ORCID Profile
0000-0002-7073-7767
Current Organisations
Helsinki Institute of Physics
,
University of Technology
,
VTT Technical Research Centre of Finland
,
University of Helsinki
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Publications
Study of quark and gluon jet substructure in Z+jet and dijet events from pp collisions
Publisher: Springer Science and Business Media LLC
Date: 2022
Abstract: Measurements of jet substructure describing the composition of quark- and gluon-initiated jets are presented. Proton-proton (pp) collision data at $$ \\sqrt{s} $$ s = 13 TeV collected with the CMS detector are used, corresponding to an integrated luminosity of 35.9 fb − 1 . Generalized angularities are measured that characterize the jet substructure and distinguish quark- and gluon-initiated jets. These observables are sensitive to the distributions of transverse momenta and angular distances within a jet. The analysis is performed using a data s le of dijet events enriched in gluon-initiated jets, and, for the first time, a Z+jet event s le enriched in quark-initiated jets. The observables are measured in bins of jet transverse momentum, and as a function of the jet radius parameter. Each measurement is repeated applying a “soft drop” grooming procedure that removes soft and large angle radiation from the jet. Using these measurements, the ability of various models to describe jet substructure is assessed, showing a clear need for improvements in Monte Carlo generators.
Measurement of the inclusive $$ \mathrm{t}\overline{\mathrm{t}} $$ production cross section in proton-proton collisions at $$ \sqrt{s} $$ = 5.02 TeV
Publisher: Springer Science and Business Media LLC
Date: 26-04-2022
Abstract: The top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data were collected in a special LHC low-energy and low-intensity run in 2017, and correspond to an integrated luminosity of 302 pb − 1 . The measurement is performed using events with one electron and one muon of opposite charge, and at least two jets. The measured cross section is 60 . 7 ± 5 . 0 (stat) ± 2 . 8 (syst) ± 1 . 1 (lumi) pb. A combination with the result in the single lepton + jets channel, based on data collected in 2015 at the same center-of-mass energy and corresponding to an integrated luminosity of 27.4 pb − 1 , is then performed. The resulting measured value is 63 . 0 ± 4 . 1 (stat) ± 3 . 0 (syst+lumi) pb, in agreement with the standard model prediction of $$ {66.8}_{-3.1}^{+2.9} $$ 66.8 − 3.1 + 2.9 pb.
Measurement of the electroweak production of
Z γ
Publisher: American Physical Society (APS)
Date: 05-10-2021
Search for a light charged Higgs boson in the
H ±
Publisher:
American Physical Society (APS)
Date:
05-10-2020
Publisher: American Physical Society (APS)
Date: 05-10-2020
Precision measurement of the
W
Publisher: American Physical Society (APS)
Date: 26-04-2022
Measurement of CKM matrix elements in single top quark t-channel production in proton-proton collisions at
Publisher:
Elsevier BV
Date:
09-2020
Publisher: Elsevier BV
Date: 09-2020
Measurement of prompt and nonprompt charmonium suppression in $$\text {PbPb}$$ collisions at 5.02$$\,\text {Te}\text {V}$$
Publisher: Springer Science and Business Media LLC
Date: 06-2018
DOI: 10.1140/EPJC/S10052-018-5950-6
Abstract: The nuclear modification factors of $${\mathrm {J}/\psi }$$ J / ψ and $$\psi \text {(2S)}$$ ψ (2S) mesons are measured in $$\text {PbPb}$$ PbPb collisions at a centre-of-mass energy per nucleon pair of $$\sqrt{\smash [b]{s_{_{\text {NN}}}}} = 5.02\,\text {Te}\text {V} $$ s NN = 5.02 TeV . The analysis is based on $$\text {PbPb}$$ PbPb and $$\mathrm {p}\mathrm {p}$$ p p data s les collected by CMS at the LHC in 2015, corresponding to integrated luminosities of 464 $$\,\mu \mathrm {b}^{-1}$$ μ b - 1 and 28 $$\,\text {pb}^\text {-1}$$ pb -1 , respectively. The measurements are performed in the dimuon rapidity range of $$|y | 2.4$$ | y | 2.4 as a function of centrality, rapidity, and transverse momentum ( $$p_{\mathrm {T}}$$ p T ) from $$p_{\mathrm {T}} =3$$ p T = 3 $${\,\text {Ge}\text {V}/}\text {c}$$ GeV / c in the most forward region and up to 50 $${\,\text {Ge}\text {V}/}\text {c}$$ GeV / c . Both prompt and nonprompt (coming from b hadron decays) $${\mathrm {J}/\psi }$$ J / ψ mesons are observed to be increasingly suppressed with centrality, with a magnitude similar to the one observed at $$\sqrt{\smash [b]{s_{_{\text {NN}}}}} = 2.76\,\text {Te}\text {V} $$ s NN = 2.76 TeV for the two $${\mathrm {J}/\psi }$$ J / ψ meson components. No dependence on rapidity is observed for either prompt or nonprompt $${\mathrm {J}/\psi }$$ J / ψ mesons. An indication of a lower prompt $${\mathrm {J}/\psi }$$ J / ψ meson suppression at $$p_{\mathrm {T}} 25$$ p T 25 $${\,\text {Ge}\text {V}/}\text {c}$$ GeV / c is seen with respect to that observed at intermediate $$p_{\mathrm {T}}$$ p T . The prompt $$\psi \text {(2S)}$$ ψ (2S) meson yield is found to be more suppressed than that of the prompt $${\mathrm {J}/\psi }$$ J / ψ mesons in the entire $$p_{\mathrm {T}}$$ p T range.
Search for new physics in the lepton plus missing transverse momentum final state in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 07-2022
Abstract: A search for physics beyond the standard model (SM) in final states with an electron or muon and missing transverse momentum is presented. The analysis uses data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected with the CMS detector at the LHC in 2016–2018 and corresponding to an integrated luminosity of 138 fb − 1 . No significant deviation from the SM prediction is observed. Model-independent limits are set on the production cross section of W’ bosons decaying into lepton-plus-neutrino final states. Within the framework of the sequential standard model, with the combined results from the electron and muon decay channels a W’ boson with mass less than 5.7 TeV is excluded at 95% confidence level. Results on a SM precision test, the determination of the oblique electroweak W parameter, are presented using LHC data for the first time. These results together with those from the direct W’ resonance search are used to extend existing constraints on composite Higgs scenarios. This is the first experimental exclusion on compositeness parameters using results from LHC data other than Higgs boson measurements.
Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 11-2021
Abstract: A search is presented for new particles produced at the LHC in proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data s le corresponding to an integrated luminosity of 101 fb − 1 , collected in 2017–2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data s le of 36 fb − 1 , collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control s les in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.
In-medium modification of dijets in PbPb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV
Publisher: Springer Science and Business Media LLC
Date: 2021
Abstract: Modifications to the distribution of charged particles with respect to high transverse momentum ( p T ) jets passing through a quark-gluon plasma are explored using the CMS detector. Back-to-back dijets are analyzed in lead-lead and proton-proton collisions at $$ \\sqrt{s_{\\mathrm{NN}}} $$ s NN = 5 . 02 TeV via correlations of charged particles in bins of relative pseudorapidity and angular distance from the leading and subleading jet axes. In comparing the lead-lead and proton-proton collision results, modifications to the charged-particle relative distance distribution and to the momentum distributions around the jet axis are found to depend on the dijet momentum balance x j , which is the ratio between the subleading and leading jet p T . For events with x j ≈ 1, these modifications are observed for both the leading and subleading jets. However, while subleading jets show significant modifications for events with a larger dijet momentum imbalance, much smaller modifications are found for the leading jets in these events.
Measurements of production cross sections of polarized same-sign W boson pairs in association with two jets in proton-proton collisions at
Publisher:
Elsevier BV
Date:
2021
Publisher: Elsevier BV
Date: 2021
Search for electroweak production of charginos and neutralinos in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 26-04-2022
Abstract: A direct search for electroweak production of charginos and neutralinos is presented. Events with three or four leptons, with up to two hadronically decaying τ leptons, or two same-sign light leptons are analyzed. The data s le consists of 137 fb − 1 of proton-proton collisions with a center of mass energy of 13 TeV, recorded with the CMS detector at the LHC. The results are interpreted in terms of several simplified models. These represent a broad range of production and decay scenarios for charginos and neutralinos. A parametric neural network is used to target several of the models with large backgrounds. In addition, results using orthogonal search regions are provided for all the models, simplifying alternative theoretical interpretations of the results. Depending on the model hypotheses, charginos and neutralinos with masses up to values between 300 and 1450 GeV are excluded at 95% confidence level.
Measurement of the top quark mass using events with a single reconstructed top quark in pp collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 12-2021
Abstract: A measurement of the top quark mass is performed using a data s le enriched with single top quark events produced in the t channel. The study is based on proton- proton collision data, corresponding to an integrated luminosity of 35.9 fb − 1 , recorded at $$ \\sqrt{s} $$ s = 13 TeV by the CMS experiment at the LHC in 2016. Candidate events are selected by requiring an isolated high-momentum lepton (muon or electron) and exactly two jets, of which one is identified as originating from a bottom quark. Multivariate discriminants are designed to separate the signal from the background. Optimized thresholds are placed on the discriminant outputs to obtain an event s le with high signal purity. The top quark mass is found to be $$ {172.13}_{-0.77}^{+0.76} $$ 172.13 − 0.77 + 0.76 GeV, where the uncertainty includes both the statistical and systematic components, reaching sub-GeV precision for the first time in this event topology. The masses of the top quark and antiquark are also determined separately using the lepton charge in the final state, from which the mass ratio and difference are determined to be $$ {0.9952}_{-0.0104}^{+0.0079} $$ 0.9952 − 0.0104 + 0.0079 and $$ {0.83}_{-1.35}^{+1.79} $$ 0.83 − 1.35 + 1.79 GeV, respectively. The results are consistent with CPT invariance.
Identification of hadronic tau lepton decays using a deep neural network
Publisher: IOP Publishing
Date: 07-2022
DOI: 10.1088/1748-0221/17/07/P07023
Abstract: A new algorithm is presented to discriminate reconstructed hadronic decays of tau leptons ( τ h ) that originate from genuine tau leptons in the CMS detector against τ h candidates that originate from quark or gluon jets, electrons, or muons. The algorithm inputs information from all reconstructed particles in the vicinity of a τ h candidate and employs a deep neural network with convolutional layers to efficiently process the inputs. This algorithm leads to a significantly improved performance compared with the previously used one. For ex le, the efficiency for a genuine τ h to pass the discriminator against jets increases by 10–30% for a given efficiency for quark and gluon jets. Furthermore, a more efficient τ h reconstruction is introduced that incorporates additional hadronic decay modes. The superior performance of the new algorithm to discriminate against jets, electrons, and muons and the improved τ h reconstruction method are validated with LHC proton-proton collision data at √ s = 13 TeV.
Measurement of single-diffractive dijet production in proton–proton collisions at $$\sqrt{s} = 8\,\text {Te}\text {V} $$ with the CMS and TOTEM experiments
Publisher: Springer Science and Business Media LLC
Date: 12-2020
DOI: 10.1140/EPJC/S10052-020-08562-Y
Abstract: Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss $$\xi $$ ξ and the four-momentum transfer squared t . Both processes $${\text{ p }{}{}} {\text{ p }{}{}} \rightarrow {\text{ p }{}{}} {\text{ X }} $$ p p → p X and $${\text{ p }{}{}} {\text{ p }{}{}} \rightarrow {\text{ X }} {\text{ p }{}{}} $$ p p → X p , i.e. with the proton scattering to either side of the interaction point, are measured, where $${\text{ X }} $$ X includes at least two jets the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton–proton collisions at $$\sqrt{s} = 8\,\text {Te}\text {V} $$ s = 8 Te during a dedicated run with $$\beta ^{*} = 90\,\text {m} $$ β ∗ = 90 m at low instantaneous luminosity and correspond to an integrated luminosity of $$37.5{\,\text {nb}^{-1}} $$ 37.5 nb - 1 . The single-diffractive dijet cross section $$\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}$$ σ jj p X , in the kinematic region $$\xi 0.1$$ ξ 0.1 , $$0.03 |t | 1\,\text {Ge}\text {V} ^2$$ 0.03 | t | 1 Ge 2 , with at least two jets with transverse momentum $$p_{\mathrm {T}} 40\,\text {Ge}\text {V} $$ p T 40 Ge , and pseudorapidity $$|\eta | 4.4$$ | η | 4.4 , is $$21.7 \pm 0.9\,\text {(stat)} \,^{+3.0}_{-3.3}\,\text {(syst)} \pm 0.9\,\text {(lumi)} \,\text {nb} $$ 21.7 ± 0.9 (stat) - 3.3 + 3.0 (syst) ± 0.9 (lumi) nb . The ratio of the single-diffractive to inclusive dijet yields, normalised per unit of $$\xi $$ ξ , is presented as a function of x , the longitudinal momentum fraction of the proton carried by the struck parton. The ratio in the kinematic region defined above, for x values in the range $$-2.9 \le \log _{10} x \le -1.6$$ - 2.9 ≤ log 10 x ≤ - 1.6 , is $$R = (\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}/\Delta \xi )/\sigma _{\mathrm {jj}} = 0.025 \pm 0.001\,\text {(stat)} \pm 0.003\,\text {(syst)} $$ R = ( σ jj p X / Δ ξ ) / σ jj = 0.025 ± 0.001 (stat) ± 0.003 (syst) , where $$\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}$$ σ jj p X and $$\sigma _{\mathrm {jj}}$$ σ jj are the single-diffractive and inclusive dijet cross sections, respectively. The results are compared with predictions from models of diffractive and nondiffractive interactions. Monte Carlo predictions based on the HERA diffractive parton distribution functions agree well with the data when corrected for the effect of soft rescattering between the spectator partons.
Search for a W′ boson decaying to a vector-like quark and a top or bottom quark in the all-jets final state at $$ \sqrt{\mathrm{s}} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 13-09-2022
Abstract: A search is presented for a heavy W′ boson resonance decaying to a B or T vector-like quark and a t or a b quark, respectively. The analysis is performed using proton-proton collisions collected with the CMS detector at the LHC. The data correspond to an integrated luminosity of 138 fb − 1 at a center-of-mass energy of 13 TeV. Both decay channels result in a signature with a t quark, a Higgs or Z boson, and a b quark, each produced with a significant Lorentz boost. The all-hadronic decays of the Higgs or Z boson and of the t quark are selected using jet substructure techniques to reduce standard model backgrounds, resulting in a distinct three-jet W′ boson decay signature. No significant deviation in data with respect to the standard model background prediction is observed. Upper limits are set at 95% confidence level on the product of the W′ boson cross section and the final state branching fraction. A W′ boson with a mass below 3.1 TeV is excluded, given the benchmark model assumption of democratic branching fractions. In addition, limits are set based on generalizations of these assumptions. These are the most sensitive limits to date for this final state.
Measurement of the azimuthal anisotropy of and mesons in PbPb collisions at
Publisher:
Elsevier BV
Date:
08-2021
Publisher: Elsevier BV
Date: 08-2021
Measurements of $${\mathrm{p}} {\mathrm{p}} \rightarrow {\mathrm{Z}} {\mathrm{Z}} $$ production cross sections and constraints on anomalous triple gauge couplings at $$\sqrt{s} = 13\,\text {TeV} $$
Publisher: Springer Science and Business Media LLC
Date: 03-2021
DOI: 10.1140/EPJC/S10052-020-08817-8
Abstract: The production of Z boson pairs in proton–proton ( $${\\mathrm{p}} {\\mathrm{p}} $$ p p ) collisions, $${{\\mathrm{p}} {\\mathrm{p}} \\rightarrow ({\\mathrm{Z}}/\\gamma ^*)({\\mathrm{Z}}/\\gamma ^*) \\rightarrow 2\\ell 2\\ell '}$$ p p → ( Z / γ ∗ ) ( Z / γ ∗ ) → 2 ℓ 2 ℓ ′ , where $${\\ell ,\\ell ' = {\\mathrm{e}}}$$ ℓ , ℓ ′ = e or $${{\\upmu }}$$ μ , is studied at a center-of-mass energy of 13 $$\\,\\text {TeV}$$ TeV with the CMS detector at the CERN LHC. The data s le corresponds to an integrated luminosity of 137 $$\\,\\text {fb}^{-1}$$ fb - 1 , collected during 2016–2018. The $${\\mathrm{Z}} {\\mathrm{Z}} $$ Z Z production cross section, $$\\sigma _{\\text {tot}} ({\\mathrm{p}} {\\mathrm{p}} \\rightarrow {\\mathrm{Z}} {\\mathrm{Z}} ) = 17.4 \\pm 0.3 \\,\\text {(stat)} \\pm 0.5 \\,\\text {(syst)} \\pm 0.4 \\,\\text {(theo)} \\pm 0.3 \\,\\text {(lumi)} \\text { pb} $$ σ tot ( p p → Z Z ) = 17.4 ± 0.3 (stat) ± 0.5 (syst) ± 0.4 (theo) ± 0.3 (lumi) pb , measured for events with two pairs of opposite-sign, same-flavor leptons produced in the mass region $${60 m_{\\ell ^+\\ell ^-} 120\\,\\text {GeV}}$$ 60 m ℓ + ℓ - 120 GeV is consistent with standard model predictions. Differential cross sections are also measured and agree with theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous $${\\mathrm{Z}} {\\mathrm{Z}} {\\mathrm{Z}} $$ Z Z Z and $${{\\mathrm{Z}} {\\mathrm{Z}} \\gamma }$$ Z Z γ couplings.
Search for the flavor-changing neutral current interactions of the top quark and the Higgs boson which decays into a pair of b quarks at $$ \sqrt{s}=13 $$ TeV
Publisher: Springer Science and Business Media LLC
Date: 06-2018
Abstract: A search for flavor-changing neutral currents (FCNC) in events with the top quark and the Higgs boson is presented. The Higgs boson decay to a pair of b quarks is considered. The data s le corresponds to an integrated luminosity of 35.9 fb −1 recorded by the CMS experiment at the LHC in proton-proton collisions at $$ \\sqrt{s}=13 $$ s = 13 TeV. Two channels are considered: single top quark FCNC production in association with the Higgs boson (pp → tH), and top quark pair production with FCNC decay of the top quark (t → qH). Final states with one isolated lepton and at least three reconstructed jets, among which at least two are associated with b quarks, are studied. No significant deviation is observed from the predicted background. Observed (expected) upper limits at 95% confidence level are set on the branching fractions of top quark decays, ℬ(t → uH) 0.47% (0.34%) and ℬ(t → cH) 0.47% (0.44%), assuming a single nonzero FCNC coupling.
Search for top squark production in fully hadronic final states in proton-proton collisions at
s <
Publisher: American Physical Society (APS)
Date: 10-09-2021
Measurement of
W ± γ
Publisher: American Physical Society (APS)
Date: 09-03-2022
W + W −
Publisher: American Physical Society (APS)
Date: 09-11-2020
Search for invisible decays of the Higgs boson produced via vector boson fusion in proton-proton collisions at
Publisher:
American Physical Society (APS)
Date:
20-05-2022
Publisher: American Physical Society (APS)
Date: 20-05-2022
Constraints on anomalous Higgs boson couplings to vector bosons and fermions in its production and decay using the four-lepton final state
Publisher: American Physical Society (APS)
Date: 17-09-2021
Measurement of
B c (
Publisher:
American Physical Society (APS)
Date:
16-11-2020
Publisher: American Physical Society (APS)
Date: 16-11-2020
Measurement of double-parton scattering in inclusive production of four jets with low transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 2022
Abstract: A measurement of inclusive four-jet production in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. The transverse momenta of jets within |η| 4 . 7 are required to exceed 35, 30, 25, and 20 GeV for the first-, second-, third-, and fourth-leading jet, respectively. Differential cross sections are measured as functions of the jet transverse momentum, jet pseudorapidity, and several other observables that describe the angular correlations between the jets. The measured distributions show sensitivity to different aspects of the underlying event, parton shower modeling, and matrix element calculations. In particular, the interplay between angular correlations caused by parton shower and double-parton scattering contributions is shown to be important. The double-parton scattering contribution is extracted by means of a template fit to the data, using distributions for single-parton scattering obtained from Monte Carlo event generators and a double-parton scattering distribution constructed from inclusive single-jet events in data. The effective double-parton scattering cross section is calculated and discussed in view of previous measurements and of its dependence on the models used to describe the single- parton scattering background.
Pileup mitigation at CMS in 13 TeV data
Publisher: IOP Publishing
Date: 15-09-2020
Measurement of differential
t t ¯ <
Publisher: American Physical Society (APS)
Date: 19-03-2021
Inclusive and differential cross section measurements of single top quark production in association with a Z boson in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 02-2022
Abstract: Inclusive and differential cross sections of single top quark production in association with a Z boson are measured in proton-proton collisions at a center-of-mass energy of 13 TeV with a data s le corresponding to an integrated luminosity of 138 fb − 1 recorded by the CMS experiment. Events are selected based on the presence of three leptons, electrons or muons, associated with leptonic Z boson and top quark decays. The measurement yields an inclusive cross section of $$ {87.9}_{-7.3}^{+7.5}{\\left(\\mathrm{stat}\\right)}_{-6.0}^{+7.3}\\left(\\mathrm{syst}\\right) $$ 87.9 − 7.3 + 7.5 stat − 6.0 + 7.3 syst fb for a dilepton invariant mass greater than 30 GeV, in agreement with standard model (SM) calculations and represents the most precise determination to date. The ratio between the cross sections for the top quark and the top antiquark production in association with a Z boson is measured as $$ {2.37}_{-0.42}^{+0.56}{\\left(\\mathrm{stat}\\right)}_{-0.13}^{+0.27}\\left(\\mathrm{syst}\\right) $$ 2.37 − 0.42 + 0.56 stat − 0.13 + 0.27 syst . Differential measurements at parton and particle levels are performed for the first time. Several kinematic observables are considered to study the modeling of the process. Results are compared to theoretical predictions with different assumptions on the source of the initial-state b quark and found to be in agreement, within the uncertainties. Additionally, the spin asymmetry, which is sensitive to the top quark polarization, is determined from the differential distribution of the polarization angle at parton level to be 0 . 54 ± 0 . 16 (stat) ± 0 . 06 (syst), in agreement with SM predictions.
Constraints on the
χ c 1 Publisher:
American Physical Society (APS)
Date:
24-04-2020
Publisher: American Physical Society (APS)
Date: 24-04-2020
Measurements of
t t
Publisher:
American Physical Society (APS)
Date:
05-08-2020
Publisher: American Physical Society (APS)
Date: 05-08-2020
Search for the rare decay of the W boson into a pion and a photon in proton-proton collisions at
Publisher: Elsevier BV
Date: 08-2021
Measurement of the Y(1S) pair production cross section and search for resonances decaying to Y(1S)μ+μ− in proton-proton collisions at
Publisher:
Elsevier BV
Date:
09-2020
Publisher: Elsevier BV
Date: 09-2020
Evidence for Higgs boson decay to a pair of muons
Publisher: Springer Science and Business Media LLC
Date: 2021
Abstract: Evidence for Higgs boson decay to a pair of muons is presented. This result combines searches in four exclusive categories targeting the production of the Higgs boson via gluon fusion, via vector boson fusion, in association with a vector boson, and in association with a top quark-antiquark pair. The analysis is performed using proton-proton collision data at $$ \\sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 137 fb − 1 , recorded by the CMS experiment at the CERN LHC. An excess of events over the back- ground expectation is observed in data with a significance of 3.0 standard deviations, where the expectation for the standard model (SM) Higgs boson with mass of 125.38 GeV is 2.5. The combination of this result with that from data recorded at $$ \\sqrt{s} $$ s = 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.7 fb − 1 , respectively, increases both the expected and observed significances by 1%. The measured signal strength, relative to the SM prediction, is $$ {1.19}_{-0.39}^{+0.40}{\\left(\\mathrm{stat}\\right)}_{-0.14}^{+0.15}\\left(\\mathrm{syst}\\right) $$ 1.19 − 0.39 + 0.40 stat − 0.14 + 0.15 syst . This result constitutes the first evidence for the decay of the Higgs boson to second generation fermions and is the most precise measurement of the Higgs boson coupling to muons reported to date.
Measurements of Higgs boson production cross sections and couplings in the diphoton decay channel at $$ \sqrt{\mathrm{s}} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 07-2021
Abstract: Measurements of Higgs boson production cross sections and couplings in events where the Higgs boson decays into a pair of photons are reported. Events are selected from a s le of proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV collected by the CMS detector at the LHC from 2016 to 2018, corresponding to an integrated luminosity of 137 fb − 1 . Analysis categories enriched in Higgs boson events produced via gluon fusion, vector boson fusion, vector boson associated production, and production associated with top quarks are constructed. The total Higgs boson signal strength, relative to the standard model (SM) prediction, is measured to be 1 . 12±0 . 09. Other properties of the Higgs boson are measured, including SM signal strength modifiers, production cross sections, and its couplings to other particles. These include the most precise measurements of gluon fusion and vector boson fusion Higgs boson production in several different kinematic regions, the first measurement of Higgs boson production in association with a top quark pair in five regions of the Higgs boson transverse momentum, and an upper limit on the rate of Higgs boson production in association with a single top quark. All results are found to be in agreement with the SM expectations.
Search for W′ bosons decaying to a top and a bottom quark at s
Publisher:
Elsevier BV
Date:
09-2021
Publisher: Elsevier BV
Date: 09-2021
Measurement of prompt D0 and D
Publisher:
Elsevier BV
Date:
05-2021
Publisher: Elsevier BV
Date: 05-2021
A Deep Neural Network for Simultaneous Estimation of b Jet Energy and Resolution
Publisher: Springer Science and Business Media LLC
Date: 30-10-2020
DOI: 10.1007/S41781-020-00041-Z
Abstract: We describe a method to obtain point and dispersion estimates for the energies of jets arising from b quarks produced in proton–proton collisions at an energy of $$\\sqrt{s}=13\\,\\text {TeV} $$ s = 13 TeV at the CERN LHC. The algorithm is trained on a large s le of simulated b jets and validated on data recorded by the CMS detector in 2017 corresponding to an integrated luminosity of 41 $$\\,\\text {fb}^{-1}$$ fb - 1 . A multivariate regression algorithm based on a deep feed-forward neural network employs jet composition and shape information, and the properties of reconstructed secondary vertices associated with the jet. The results of the algorithm are used to improve the sensitivity of analyses that make use of b jets in the final state, such as the observation of Higgs boson decay to $$\\hbox {b}\\bar{\\hbox {b}}$$ b b ¯ .
Measurement of differential cross sections and charge ratios for t-channel single top quark production in proton–proton collisions at $$\sqrt{s}=13$$ $$\,\text {Te}\text {V}$$
Publisher: Springer Science and Business Media LLC
Date: 05-2020
DOI: 10.1140/EPJC/S10052-020-7858-1
Abstract: A measurement is presented of differential cross sections for t -channel single top quark and antiquark production in proton–proton collisions at a centre-of-mass energy of 13 $$\\,\\text {Te}\\text {V}$$ Te by the CMS experiment at the LHC. From a data set corresponding to an integrated luminosity of 35.9 $$\\,\\text {fb}^{-1}$$ fb - 1 , events containing one muon or electron and two or three jets are analysed. The cross section is measured as a function of the top quark transverse momentum ( $$p_{\\mathrm{T}} $$ p T ), rapidity, and polarisation angle, the charged lepton $$p_{\\mathrm{T}} $$ p T and rapidity, and the $$p_{\\mathrm{T}} $$ p T of the $$\\text {W}{}{}$$ W boson from the top quark decay. In addition, the charge ratio is measured differentially as a function of the top quark, charged lepton, and $$\\text {W}{}{}$$ W boson kinematic observables. The results are found to be in agreement with standard model predictions using various next-to-leading-order event generators and sets of parton distribution functions. Additionally, the spin asymmetry, sensitive to the top quark polarisation, is determined from the differential distribution of the polarisation angle at parton level to be $$0.440 \\pm 0.070$$ 0.440 ± 0.070 , in agreement with the standard model prediction.
Studies of charm and beauty hadron long-range correlations in pp and pPb collisions at LHC energies
Publisher: Elsevier BV
Date: 02-2021
Measurement of the top quark forward-backward production asymmetry and the anomalous chromoelectric and chromomagnetic moments in pp collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 06-2020
Observation of B$$^0$$ $$\rightarrow $$ $$\uppsi $$(2S)K$$^0_\mathrm {S}\uppi ^+\uppi ^-$$ and B$$^0_\mathrm {s}$$ $$\rightarrow $$ $$\uppsi $$(2S)K$$^0_\mathrm {S}$$ decays
Publisher: Springer Science and Business Media LLC
Date: 05-2022
DOI: 10.1140/EPJC/S10052-022-10315-Y
Abstract: Using a data s le of $$\\sqrt{s}=13\\,\\text {TeV}$$ s = 13 TeV proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of $$103\\text {~fb}^{-1}$$ 103 fb - 1 , the $$\\text {B}^{0}_{\\mathrm{s}} \\rightarrow \\uppsi (\\text {2S})\\text {K}_\\mathrm{S}^{0}$$ B s 0 → ψ ( 2S ) K S 0 and $$\\text {B}^{0} \\rightarrow \\uppsi (\\text {2S})\\text {K}_\\mathrm{S}^{0} \\uppi ^+\\uppi ^-$$ B 0 → ψ ( 2S ) K S 0 π + π - decays are observed with significances exceeding 5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to $${\\mathcal {B}}(\\text {B}^{0}_{\\mathrm{s}} \\rightarrow \\uppsi (\\text {2S})K_\\mathrm{S}^{0})/{\\mathcal {B}}(\\text {B}^{0}\\rightarrow \\uppsi (\\text {2S})K_\\mathrm{S}^{0}) = (3.33 \\pm 0.69 (\\text {stat})\\, \\pm 0.11\\,(\\text {syst}) \\pm 0.34\\,(f_{\\mathrm{s}}/f_{\\mathrm{d}})) \\times 10^{-2}$$ B ( B s 0 → ψ ( 2S ) K S 0 ) / B ( B 0 → ψ ( 2S ) K S 0 ) = ( 3.33 ± 0.69 ( stat ) ± 0.11 ( syst ) ± 0.34 ( f s / f d ) ) × 10 - 2 and $${\\mathcal {B}}(\\text {B}^{0} \\rightarrow \\uppsi (\\text {2S})\\text {K}_\\mathrm{S}^{0} \\uppi ^{+} \\uppi ^{-})/ {\\mathcal {B}}(\\text {B}^{0} \\rightarrow \\uppsi (\\text {2S})\\text {K}^{0}_{\\mathrm{S}}) = 0.480 \\pm 0.013\\,(\\text {stat}) \\pm 0.032\\,(\\text {syst})$$ B ( B 0 → ψ ( 2S ) K S 0 π + π - ) / B ( B 0 → ψ ( 2S ) K S 0 ) = 0.480 ± 0.013 ( stat ) ± 0.032 ( syst ) , where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of $$\\hbox {B}^{0}_{\\mathrm{s}}$$ B s 0 and $$\\hbox {B}^{0}$$ B 0 mesons, $$f_{\\mathrm{s}}/f_{\\mathrm{d}}$$ f s / f d .
Search for resonant pair production of Higgs bosons in the
b b Z Z
Publisher:
American Physical Society (APS)
Date:
12-08-2020
Publisher: American Physical Society (APS)
Date: 12-08-2020
Measurements of the
W
Publisher: American Physical Society (APS)
Date: 30-11-2020
Observation of triple J/ψ meson production in proton-proton collisions
Publisher: Springer Science and Business Media LLC
Date: 19-01-2023
DOI: 10.1038/S41567-022-01838-Y
Abstract: Protons consist of three valence quarks, two up-quarks and one down-quark, held together by gluons and a sea of quark-antiquark pairs. Collectively, quarks and gluons are referred to as partons. In a proton-proton collision, typically only one parton of each proton undergoes a hard scattering – referred to as single-parton scattering – leaving the remainder of each proton only slightly disturbed. Here, we report the study of double- and triple-parton scatterings through the simultaneous production of three J/ ψ mesons, which consist of a charm quark-antiquark pair, in proton-proton collisions recorded with the CMS experiment at the Large Hadron Collider. We observed this process – reconstructed through the decays of J/ ψ mesons into pairs of oppositely charged muons – with a statistical significance above five standard deviations. We measured the inclusive fiducial cross-section to be $$27{2}_{-104}^{+141}\\,{{{\\rm{(stat)}}}}\\,\\pm 17\\,{{{\\rm{(syst)}}}}\\,{{{\\rm{fb}}}}\\,$$ 27 2 − 104 + 141 (stat) ± 17 (syst) fb , and compared it to theoretical expectations for triple-J/ ψ meson production in single-, double- and triple-parton scattering scenarios. Assuming factorization of multiple hard-scattering probabilities in terms of single-parton scattering cross-sections, double- and triple-parton scattering are the dominant contributions for the measured process.
Search for top squarks in final states with two top quarks and several light-flavor jets in proton-proton collisions at
Publisher:
American Physical Society (APS)
Date:
20-08-2021
Publisher: American Physical Society (APS)
Date: 20-08-2021
Measurements of the Electroweak Diboson Production Cross Sections in Proton-Proton Collisions at
Publisher:
American Physical Society (APS)
Date:
02-11-2021
Publisher: American Physical Society (APS)
Date: 02-11-2021
Inclusive nonresonant multilepton probes of new phenomena at
s =
Publisher:
American Physical Society (APS)
Date:
14-06-2022
Publisher: American Physical Society (APS)
Date: 14-06-2022
Measurement of differential
t t
Publisher:
American Physical Society (APS)
Date:
30-11-2021
Publisher: American Physical Society (APS)
Date: 30-11-2021
Measurement of the top quark Yukawa coupling from
t t
Publisher:
American Physical Society (APS)
Date:
30-11-2020
Publisher: American Physical Society (APS)
Date: 30-11-2020
Observation of the rare Bs0 →µ+µ− decay from the combined analysis of CMS and LHCb data
Publisher: Springer Science and Business Media LLC
Date: 13-05-2015
DOI: 10.1038/NATURE14474
Abstract: The standard model of particle physics describes the fundamental particles and their interactions via the strong, electromagnetic and weak forces. It provides precise predictions for measurable quantities that can be tested experimentally. The probabilities, or branching fractions, of the strange B meson (B(s)(0)) and the B0 meson decaying into two oppositely charged muons (μ+ and μ−) are especially interesting because of their sensitivity to theories that extend the standard model. The standard model predicts that the B(s)(0) →µ+µ− and B(0) →µ+µ− decays are very rare, with about four of the former occurring for every billion mesons produced, and one of the latter occurring for every ten billion B0 mesons. A difference in the observed branching fractions with respect to the predictions of the standard model would provide a direction in which the standard model should be extended. Before the Large Hadron Collider (LHC) at CERN started operating, no evidence for either decay mode had been found. Upper limits on the branching fractions were an order of magnitude above the standard model predictions. The CMS (Compact Muon Solenoid) and LHCb (Large Hadron Collider beauty) collaborations have performed a joint analysis of the data from proton–proton collisions that they collected in 2011 at a centre-of-mass energy of seven teraelectronvolts and in 2012 at eight teraelectronvolts. Here we report the first observation of the B(s)(0) → µ+µ− decay, with a statistical significance exceeding six standard deviations, and the best measurement so far of its branching fraction. Furthermore, we obtained evidence for the B(0) → µ+µ− decay with a statistical significance of three standard deviations. Both measurements are statistically compatible with standard model predictions and allow stringent constraints to be placed on theories beyond the standard model. The LHC experiments will resume taking data in 2015, recording proton–proton collisions at a centre-of-mass energy of 13 teraelectronvolts, which will approximately double the production rates of B(s)(0) and B0 mesons and lead to further improvements in the precision of these crucial tests of the standard model.
Measurement of nuclear modification factors of ϒ(1S), ϒ(2S), and ϒ(3S) mesons in PbPb collisions at
Publisher:
Elsevier BV
Date:
03-2019
Publisher: Elsevier BV
Date: 03-2019
Measurement of b jet shapes in proton-proton collisions at $$ \sqrt{s} $$ = 5.02 TeV
Publisher: Springer Science and Business Media LLC
Date: 05-2021
Abstract: We present the first study of charged-hadron production associated with jets originating from b quarks in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data s le used in this study was collected with the CMS detector at the CERN LHC and corresponds to an integrated luminosity of 27.4 pb − 1 . To characterize the jet substructure, the differential jet shapes, defined as the normalized transverse momentum distribution of charged hadrons as a function of angular distance from the jet axis, are measured for b jets. In addition to the jet shapes, the per-jet yields of charged particles associated with b jets are also quantified, again as a function of the angular distance with respect to the jet axis. Extracted jet shape and particle yield distributions for b jets are compared with results for inclusive jets, as well as with the predictions from the pythia and herwig++ event generators.
Measurement of the Inclusive and Differential Higgs Boson Production Cross Sections in the Decay Mode to a Pair of
τ<
Publisher: American Physical Society (APS)
Date: 23-02-2022
Search for Higgs boson pair production in events with two bottom quarks and two tau leptons in proton–proton collisions at
Publisher:
Elsevier BV
Date:
03-2018
Publisher: Elsevier BV
Date: 03-2018
Measurement of the associated production of a
Z
Publisher: American Physical Society (APS)
Date: 19-08-2020
Search for bottom-type, vectorlike quark pair production in a fully hadronic final state in proton-proton collisions at
Publisher:
American Physical Society (APS)
Date:
07-12-2020
Publisher: American Physical Society (APS)
Date: 07-12-2020
Search for higgsinos decaying to two Higgs bosons and missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 03-05-2022
Abstract: Results are presented from a search for physics beyond the standard model in proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV in channels with two Higgs bosons, each decaying via the process H → b $$ \\overline{\\mathrm{b}} $$ b ¯ , and large missing transverse momentum. The search uses a data s le corresponding to an integrated luminosity of 137 fb − 1 collected by the CMS experiment at the CERN LHC. The search is motivated by models of supersymmetry that predict the production of neutralinos, the neutral partners of the electroweak gauge and Higgs bosons. The observed event yields in the signal regions are found to be consistent with the standard model background expectations. The results are interpreted using simplified models of supersymmetry. For the electroweak production of nearly mass-degenerate higgsinos, each of whose decay chains yields a neutralino $$ \\left({\\overset{\\sim }{\\upchi}}_1^0\\right) $$ χ ~ 1 0 that in turn decays to a massless goldstino and a Higgs boson, $$ \\left({\\overset{\\sim }{\\upchi}}_1^0\\right) $$ χ ~ 1 0 masses in the range 175 to 1025 GeV are excluded at 95% confidence level. For the strong production of gluino pairs decaying via a slightly lighter $$ \\left({\\overset{\\sim }{\\upchi}}_2^0\\right) $$ χ ~ 2 0 to H and a light $$ \\left({\\overset{\\sim }{\\upchi}}_1^0\\right) $$ χ ~ 1 0 , gluino masses below 2330 GeV are excluded.
Search for Higgs Boson Pair Production in the Four
b
Publisher: American Physical Society (APS)
Date: 18-08-2022
Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC
Publisher: IOP Publishing
Date: 05-2021
DOI: 10.1088/1748-0221/16/05/P05014
Abstract: The performance is presented of the reconstruction and identification algorithms for electrons and photons with the CMS experiment at the LHC. The reported results are based on proton-proton collision data collected at a center-of-mass energy of 13 TeV and recorded in 2016–2018, corresponding to an integrated luminosity of 136 fb^-1. Results obtained from lead-lead collision data collected at √(s NN )=5.02 TeV are also presented. Innovative techniques are used to reconstruct the electron and photon signals in the detector and to optimize the energy resolution. Events with electrons and photons in the final state are used to measure the energy resolution and energy scale uncertainty in the recorded events. The measured energy resolution for electrons produced in Z boson decays in proton-proton collision data ranges from 2 to 5%, depending on electron pseudorapidity and energy loss through bremsstrahlung in the detector material. The energy scale in the same range of energies is measured with an uncertainty smaller than 0.1 (0.3)% in the barrel (endcap) region in proton-proton collisions and better than 1 (3)% in the barrel (endcap) region in heavy ion collisions. The timing resolution for electrons from Z boson decays with the full 2016–2018 proton-proton collision data set is measured to be 200 ps.
Search for a heavy Higgs boson decaying into two lighter Higgs bosons in the ττbb final state at 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 11-2021
Abstract: A search for a heavy Higgs boson H decaying into the observed Higgs boson h with a mass of 125 GeV and another Higgs boson h S is presented. The h and h S bosons are required to decay into a pair of tau leptons and a pair of b quarks, respectively. The search uses a s le of proton-proton collisions collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb −1 . Mass ranges of 240–3000 GeV for m H and 60–2800 GeV for $$ {m}_{{\\mathrm{h}}_{\\mathrm{S}}} $$ m h S are explored in the search. No signal has been observed. Model independent 95% confidence level upper limits on the product of the production cross section and the branching fractions of the signal process are set with a sensitivity ranging from 125 fb (for m H = 240 GeV) to 2 . 7 fb (for m H = 1000 GeV). These limits are compared to maximally allowed products of the production cross section and the branching fractions of the signal process in the next-to-minimal supersymmetric extension of the standard model.
Search for a heavy resonance decaying into a top quark and a W boson in the lepton+jets final state at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 08-04-2022
Abstract: A search for a heavy resonance decaying into a top quark and a W boson in proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV is presented. The data analyzed were recorded with the CMS detector at the LHC and correspond to an integrated luminosity of 138 fb − 1 . The top quark is reconstructed as a single jet and the W boson, from its decay into an electron or muon and the corresponding neutrino. A top quark tagging technique based on jet clustering with a variable distance parameter and simultaneous jet grooming is used to identify jets from the collimated top quark decay. The results are interpreted in the context of two benchmark models, where the heavy resonance is either an excited bottom quark b ∗ or a vector-like quark B. A statistical combination with an earlier search by the CMS Collaboration in the all-hadronic final state is performed to place upper cross section limits on these two models. The new analysis extends the lower range of resonance mass probed from 1.4 down to 0.7 TeV. For left-handed, right-handed, and vector-like couplings, b ∗ masses up to 3.0, 3.0, and 3.2 TeV are excluded at 95% confidence level, respectively. The observed upper limits represent the most stringent constraints on the b ∗ model to date.
Search for a right-handed W boson and a heavy neutrino in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 08-04-2022
Abstract: A search is presented for a right-handed W boson (W R ) and a heavy neutrino (N), in a final state consisting of two same-flavor leptons (ee or μμ) and two quarks. The search is performed with the CMS experiment at the CERN LHC using a data s le of proton-proton collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb − 1 . The search covers two regions of phase space, one where the decay products of the heavy neutrino are merged into a single large-area jet, and one where the decay products are well separated. The expected signal is characterized by an excess in the invariant mass distribution of the final-state objects. No significant excess over the standard model background expectations is observed. The observations are interpreted as upper limits on the product of W R production cross sections and branching fractions assuming that couplings are identical to those of the standard model W boson. For N masses m N equal to half the W R mass $$ {m}_{{\\mathrm{W}}_{\\mathrm{R}}} $$ m W R ( m N = 0 . 2 TeV), $$ {m}_{{\\mathrm{W}}_{\\mathrm{R}}} $$ m W R is excluded at 95% confidence level up to 4.7 (4.8) and 5.0 (5.4) TeV for the electron and muon channels, respectively. This analysis provides the most stringent limits on the W R mass to date.
First measurement of the cross section for top quark pair production with additional charm jets using dileptonic final states in pp collisions at
Publisher:
Elsevier BV
Date:
09-2021
Publisher: Elsevier BV
Date: 09-2021
Search for Long-Lived Particles Decaying in the CMS End Cap Muon Detectors in Proton-Proton Collisions at
Publisher:
American Physical Society (APS)
Date:
23-12-2021
Publisher: American Physical Society (APS)
Date: 23-12-2021
Search for singly and pair-produced leptoquarks coupling to third-generation fermions in proton-proton collisions at
Publisher:
Elsevier BV
Date:
08-2021
Publisher: Elsevier BV
Date: 08-2021
Fragmentation of jets containing a prompt J/ψ meson in PbPb and pp collisions at
Publisher:
Elsevier BV
Date:
02-2022
Publisher: Elsevier BV
Date: 02-2022
Determination of the strong coupling constant αS(mZ) from measurements of inclusive W± and Z boson production cross sections in proton-proton collisions at $$ \sqrt{\mathrm{s}} $$ = 7 and 8 TeV
Publisher: Springer Science and Business Media LLC
Date: 06-2020
Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
Publisher: Elsevier BV
Date: 09-2012
Correlations of azimuthal anisotropy Fourier harmonics with subevent cumulants in
p Pb Publisher:
American Physical Society (APS)
Date:
14-01-2021
Publisher: American Physical Society (APS)
Date: 14-01-2021
Search for top squark pair production using dilepton final states in $${\text {p}}{\text {p}}$$ collision data collected at $$\sqrt{s}=13\,\text {TeV} $$
Publisher: Springer Science and Business Media LLC
Date: 2021
DOI: 10.1140/EPJC/S10052-020-08701-5
Abstract: A search is presented for supersymmetric partners of the top quark (top squarks) in final states with two oppositely charged leptons (electrons or muons), jets identified as originating from $${\\text {b}}$$ b quarks, and missing transverse momentum. The search uses data from proton-proton collisions at $$\\sqrt{s}=13\\,\\text {TeV} $$ s = 13 TeV collected with the CMS detector, corresponding to an integrated luminosity of 137 $$\\,{\\text {fb}}^{-1}$$ fb - 1 . Hypothetical signal events are efficiently separated from the dominant top quark pair production background with requirements on the significance of the missing transverse momentum and on transverse mass variables. No significant deviation is observed from the expected background. Exclusion limits are set in the context of simplified supersymmetric models with pair-produced lightest top squarks. For top squarks decaying exclusively to a top quark and a lightest neutralino, lower limits are placed at $$95\\%$$ 95 % confidence level on the masses of the top squark and the neutralino up to 925 and 450 $$\\,\\text {GeV}$$ GeV , respectively. If the decay proceeds via an intermediate chargino, the corresponding lower limits on the mass of the lightest top squark are set up to 850 $$\\,\\text {GeV}$$ GeV for neutralino masses below 420 $$\\,\\text {GeV}$$ GeV . For top squarks undergoing a cascade decay through charginos and sleptons, the mass limits reach up to 1.4 $$\\,\\text {TeV}$$ TeV and 900 $$\\,\\text {GeV}$$ GeV respectively for the top squark and the lightest neutralino.
Search for low-mass dilepton resonances in Higgs boson decays to four-lepton final states in proton–proton collisions at $$\sqrt{s}=13\,\text {TeV} $$
Publisher: Springer Science and Business Media LLC
Date: 04-2022
DOI: 10.1140/EPJC/S10052-022-10127-0
Abstract: A search for low-mass dilepton resonances in Higgs boson decays is conducted in the four-lepton final state. The decay is assumed to proceed via a pair of beyond the standard model particles, or one such particle and a $${\\mathrm{Z}}$$ Z boson. The search uses proton–proton collision data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 137 $$\\,\\text {fb}^{-1}$$ fb - 1 , at a center-of-mass energy $$\\sqrt{s} = 13\\,\\text {TeV} $$ s = 13 TeV . No significant deviation from the standard model expectation is observed. Upper limits at 95% confidence level are set on model-independent Higgs boson decay branching fractions. Additionally, limits on dark photon and axion-like particle production, based on two specific models, are reported.
Study of Drell-Yan dimuon production in proton-lead collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 8.16 TeV
Publisher: Springer Science and Business Media LLC
Date: 05-2013
Abstract: Differential cross sections for the Drell-Yan process, including Z boson production, using the dimuon decay channel are measured in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of 8.16 TeV. A data s le recorded with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 173 nb − 1 . The differential cross section as a function of the dimuon mass is measured in the range 15–600 GeV, for the first time in proton-nucleus collisions. It is also reported as a function of dimuon rapidity over the mass ranges 15–60 GeV and 60–120 GeV, and ratios for the p-going over the Pb-going beam directions are built. In both mass ranges, the differential cross sections as functions of the dimuon transverse momentum p T and of a geometric variable ϕ * are measured, where ϕ * highly correlates with p T but is determined with higher precision. In the Z mass region, the rapidity dependence of the data indicate a modification of the distribution of partons within a lead nucleus as compared to the proton case. The data are more precise than predictions based upon current models of parton distributions.
Measurement of the inclusive and differential WZ production cross sections, polarization angles, and triple gauge couplings in pp collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 07-2022
Abstract: The associated production of a W and a Z boson is studied in final states with multiple leptons produced in proton-proton (pp) collisions at a centre-of-mass energy of 13 TeV using 137 fb − 1 of data collected with the CMS detector at the LHC. A measurement of the total inclusive production cross section yields σ tot (pp → WZ) = 50 . 6 ± 0 . 8 (stat) ± 1 . 5 (syst) ± 1 . 1 (lumi) ± 0 . 5 (theo) pb. Measurements of the fiducial and differential cross sections for several key observables are also performed in all the final-state lepton flavour and charge compositions with a total of three charged leptons, which can be electrons or muons. All results are compared with theoretical predictions computed up to next-to-next-to-leading order in quantum chromodynamics plus next-to-leading or- der in electroweak theory and for various sets of parton distribution functions. The results include direct measurements of the charge asymmetry and the W and Z vector boson polarization. The first observation of longitudinally polarized W bosons in WZ production is reported. Anomalous gauge couplings are searched for, leading to new constraints on beyond-the-standard-model contributions to the WZ triple gauge coupling.
Performance of the CMS muon trigger system in proton-proton collisions at √(s) = 13
Publisher: IOP Publishing
Date: 07-2021
DOI: 10.1088/1748-0221/16/07/P07001
Abstract: The muon trigger system of the CMS experiment uses a combination of hardware and software to identify events containing a muon. During Run 2 (covering 2015–2018) the LHC achieved instantaneous luminosities as high as 2 × 10 34 while delivering proton-proton collisions at √(s) = 13. The challenge for the trigger system of the CMS experiment is to reduce the registered event rate from about 40MHz to about 1kHz. Significant improvements important for the success of the CMS physics program have been made to the muon trigger system via improved muon reconstruction and identification algorithms since the end of Run 1 and throughout the Run 2 data-taking period. The new algorithms maintain the acceptance of the muon triggers at the same or even lower rate throughout the data-taking period despite the increasing number of additional proton-proton interactions in each LHC bunch crossing. In this paper, the algorithms used in 2015 and 2016 and their improvements throughout 2017 and 2018 are described. Measurements of the CMS muon trigger performance for this data-taking period are presented, including efficiencies, transverse momentum resolution, trigger rates, and the purity of the selected muon s le. This paper focuses on the single- and double-muon triggers with the lowest sustainable transverse momentum thresholds used by CMS. The efficiency is measured in a transverse momentum range from 8 to several hundred.
Search for charged-lepton flavor violation in top quark production and decay in pp collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 15-06-2022
Abstract: Results are presented from a search for charged-lepton flavor violating (CLFV) interactions in top quark production and decay in pp collisions at a center-of-mass energy of 13 TeV. The events are required to contain one oppositely charged electron-muon pair in the final state, along with at least one jet identified as originating from a bottom quark. The data correspond to an integrated luminosity of 138 fb − 1 , collected by the CMS experiment at the LHC. This analysis includes both the production (q → e μ t) and decay (t → e μ q) modes of the top quark through CLFV interactions, with q referring to a u or c quark. These interactions are parametrized using an effective field theory approach. With no significant excess over the standard model expectation, the results are interpreted in terms of vector-, scalar-, and tensor-like CLFV four-fermion effective interactions. Finally, observed exclusion limits are set at 95% confidence levels on the respective branching fractions of a top quark to an e μ pair and an up (charm) quark of 0 . 13 × 10 − 6 (1 . 31 × 10 − 6 ), 0 . 07 × 10 − 6 (0 . 89 × 10 − 6 ), and 0 . 25 × 10 − 6 (2 . 59 × 10 − 6 ) for vector, scalar, and tensor CLFV interactions, respectively.
Measurements of production cross sections of WZ and same-sign WW boson pairs in association with two jets in proton-proton collisions at
Publisher:
Elsevier BV
Date:
10-2020
Publisher: Elsevier BV
Date: 10-2020
Measurement of $$\hbox {t}{\bar{\hbox {t}}}$$ normalised multi-differential cross sections in $${\text {p}}{\text {p}} $$ collisions at $$\sqrt{s}=13\,{\text {TeV}} $$, and simultaneous determination
Publisher: Springer Science and Business Media LLC
Date: 07-2020
DOI: 10.1140/EPJC/S10052-020-7917-7
Abstract: Normalised multi-differential cross sections for top quark pair ( $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ ) production are measured in proton-proton collisions at a centre-of-mass energy of 13 $$\\,{\\text {TeV}}$$ TeV using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of $$35.9{\\,{\\text {fb}}^{-1}} $$ 35.9 fb - 1 . The double-differential $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ cross section is measured as a function of the kinematic properties of the top quark and of the $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength $$\\alpha _{S}$$ α S and the top quark pole mass ( $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole ) using several sets of parton distribution functions (PDFs). The measurement of $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole exploits the sensitivity of the $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ invariant mass distribution to $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole near the production threshold. Furthermore, a simultaneous fit of the PDFs, $$\\alpha _{S}$$ α S , and $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of $$\\alpha _{S}$$ α S and $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole . The values $$\\alpha _{S}(m_{{\\text {Z}}}) = 0.1135{}^{+0.0021}_{-0.0017}$$ α S ( m Z ) = 0.1135 - 0.0017 + 0.0021 and $$m_{{\\text {t}}}^{{\\text {pole}}} = 170.5 \\pm 0.8 \\,{\\text {GeV}} $$ m t pole = 170.5 ± 0.8 GeV are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole of the order of $$+1 \\,{\\text {GeV}} $$ + 1 GeV , which can be regarded as additional theoretical uncertainty in the current $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole extraction.
First Search for Exclusive Diphoton Production at High Mass with Tagged Protons in Proton-Proton Collisions at
Publisher:
American Physical Society (APS)
Date:
28-06-2022
Publisher: American Physical Society (APS)
Date: 28-06-2022
Measurement of prompt open-charm production cross sections in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 11-2021
Abstract: The production cross sections for prompt open-charm mesons in proton-proton collisions at a center-of-mass energy of 13 TeV are reported. The measurement is performed using a data s le collected by the CMS experiment corresponding to an integrated luminosity of 29 nb − 1 . The differential production cross sections of the D ∗ ± , D ± , and D 0 $$ \left({\overline{\mathrm{D}}}^0\right) $$ D ¯ 0 mesons are presented in ranges of transverse momentum and pseudorapidity 4 p T 100 GeV and |η| 2 . 1, respectively. The results are compared to several theoretical calculations and to previous measurements.
Measurement of properties of $$ {\mathrm{B}}_{\mathrm{s}}^0 $$→ μ+μ− decays and search for B0→ μ+μ− with the CMS experiment
Publisher: Springer Science and Business Media LLC
Date: 04-2020
Search for high mass dijet resonances with a new background prediction method in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 05-2020
Search for direct top squark pair production in events with one lepton, jets, and missing transverse momentum at 13 TeV with the CMS experiment
Publisher: Springer Science and Business Media LLC
Date: 05-2020
A deep neural network to search for new long-lived particles decaying to jets
Publisher: IOP Publishing
Date: 20-08-2020
Studies of Charm Quark Diffusion inside Jets Using Pb-Pb and
p p Publisher:
American Physical Society (APS)
Date:
03-09-2020
Publisher: American Physical Society (APS)
Date: 03-09-2020
Search for heavy resonances decaying to
W W Publisher:
American Physical Society (APS)
Date:
25-02-2022
Publisher: American Physical Society (APS)
Date: 25-02-2022
Calibration of the CMS hadron calorimeters using proton-proton collision data at √s = 13 TeV
Publisher: IOP Publishing
Date: 05-05-2020
Search for a light pseudoscalar Higgs boson in the boosted μμττ final state in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 08-2020
Abstract: A search for a light pseudoscalar Higgs boson (a) decaying from the 125 GeV (or a heavier) scalar Higgs boson (H) is performed using the 2016 LHC proton-proton collision data at $$ \\sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 35 . 9 fb − 1 , collected by the CMS experiment. The analysis considers gluon fusion and vector boson fusion production of the H, followed by the decay H → aa → μμττ , and considers pseudoscalar masses in the range 3 . 6 m a 21 GeV. Because of the large mass difference between the H and the a bosons and the small masses of the a boson decay products, both the μμ and the ττ pairs have high Lorentz boost and are collimated. The ττ reconstruction efficiency is increased by modifying the standard technique for hadronic τ lepton decay reconstruction to account for a nearby muon. No significant signal is observed. Model-independent limits are set at 95% confidence level, as a function of m a , on the branching fraction (ℬ) for H → aa → μμττ , down to 1 . 5 (2 . 0) × 10 − 4 for m H = 125 (300) GeV. Model-dependent limits on ℬ(H → aa) are set within the context of two Higgs doublets plus singlet models, with the most stringent results obtained for Type-III models. These results extend current LHC searches for heavier a bosons that decay to resolved lepton pairs and provide the first such bounds for an H boson with a mass above 125 GeV.
Inclusive search for highly boosted Higgs bosons decaying to bottom quark-antiquark pairs in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 12-2020
Abstract: A search for standard model Higgs bosons (H) produced with transverse momentum ( p T ) greater than 450 GeV and decaying to bottom quark-antiquark pairs ( $$ \\mathrm{b}\\overline{\\mathrm{b}} $$ b b ¯ ) is performed using proton-proton collision data collected by the CMS experiment at the LHC at $$ \\sqrt{s} $$ s = 13 TeV. The data s le corresponds to an integrated luminosity of 137 fb − 1 . The search is inclusive in the Higgs boson production mode. Highly Lorentz-boosted Higgs bosons decaying to $$ \\mathrm{b}\\overline{\\mathrm{b}} $$ b b ¯ are reconstructed as single large-radius jets, and are identified using jet substructure and a dedicated b tagging technique based on a deep neural network. The method is validated with Z → $$ \\mathrm{b}\\overline{\\mathrm{b}} $$ b b ¯ decays. For a Higgs boson mass of 125 GeV, an excess of events above the background assuming no Higgs boson production is observed with a local significance of 2.5 standard deviations ( σ ), while the expectation is 0.7. The corresponding signal strength and local significance with respect to the standard model expectation are μ H = 3 . 7 ± 1 . 2(stat) $$ {}_{-0.7}^{+0.8} $$ − 0.7 + 0.8 (syst) $$ {}_{-0.5}^{+0.8} $$ − 0.5 + 0.8 (theo) and 1 . 9 σ . Additionally, an unfolded differential cross section as a function of Higgs boson p T for the gluon fusion production mode is presented, assuming the other production modes occur at the expected rates.
Search for new physics in dijet angular distributions using proton–proton collisions at $$\sqrt{s}=13\hbox {TeV}$$ and constraints on dark matter and other models
Publisher: Springer Science and Business Media LLC
Date: 09-2018
DOI: 10.1140/EPJC/S10052-018-6242-X
Abstract: A search is presented for physics beyond the standard model, based on measurements of dijet angular distributions in proton–proton collisions at $$\\sqrt{s}=13\\hbox {TeV}$$ s = 13 TeV . The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 35.9 $$\\,\\text {fb}^{-1}$$ fb - 1 . The observed distributions, corrected to particle level, are found to be in agreement with predictions from perturbative quantum chromodynamics that include electroweak corrections. Constraints are placed on models containing quark contact interactions, extra spatial dimensions, quantum black holes, or dark matter, using the detector-level distributions. In a benchmark model where only left-handed quarks participate, contact interactions are excluded at the 95% confidence level up to a scale of 12.8 or 17.5TeV, for destructive or constructive interference, respectively. The most stringent lower limits to date are set on the ultraviolet cutoff in the Arkani–Hamed–Dimopoulos–Dvali model of extra dimensions. In the Giudice–Rattazzi–Wells convention, the cutoff scale is excluded up to 10.1TeV. The production of quantum black holes is excluded for masses below 5.9 and 8.2TeV, depending on the model. For the first time, lower limits between 2.0 and 4.6TeVare set on the mass of a dark matter mediator for (axial-)vector mediators, for the universal quark coupling $$g_{\\mathrm {\\mathrm {q}}} =1.0$$ g q = 1.0 .
Search for a heavy vector resonance decaying to a $${\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}$$ boson and a Higgs boson in proton-proton collisions at $$\sqrt{s} = 13\,\text {Te}\text {V} $$
Publisher: Springer Science and Business Media LLC
Date: 08-2021
DOI: 10.1140/EPJC/S10052-021-09348-6
Abstract: A search is presented for a heavy vector resonance decaying into a $${\\mathrm{Z}}_{\\mathrm{}}^{\\mathrm{}}$$ Z boson and the standard model Higgs boson, where the $${\\mathrm{Z}}_{\\mathrm{}}^{\\mathrm{}}$$ Z boson is identified through its leptonic decays to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137 $$\\,\\text {fb}^{-1}$$ fb - 1 . Upper limits are derived on the production of a narrow heavy resonance $${\\mathrm{{{\\mathrm{Z}}_{\\mathrm{}}^{\\mathrm{}}}}}_{\\mathrm{}}^{\\mathrm{\\prime }}$$ Z ′ , and a mass below 3.5 and 3.7 $$\\,\\text {Te}\\text {V}$$ Te is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet $${\\mathrm{{{\\mathrm{Z}}_{\\mathrm{}}^{\\mathrm{}}}}}_{\\mathrm{}}^{\\mathrm{\\prime }}$$ Z ′ model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3 $$\\,\\text {fb}$$ fb for a $${\\mathrm{{{\\mathrm{Z}}_{\\mathrm{}}^{\\mathrm{}}}}}_{\\mathrm{}}^{\\mathrm{\\prime }}$$ Z ′ mass between 0.8 and 4.6 $$\\,\\text {Te}\\text {V}$$ Te , respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.
Search for the lepton flavor violating decay τ → 3μ in proton-proton collisions at $$ \sqrt{\mathrm{s}} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 2021
Abstract: Results are reported from a search for the lepton flavor violating decay τ → 3 μ in proton-proton collisions at $$ \\sqrt{\\mathrm{s}} $$ s = 13 TeV. The data s le corresponds to an integrated luminosity of 33.2 fb − 1 recorded by the CMS experiment at the LHC in 2016. The search exploits τ leptons produced in both W boson and heavy-flavor hadron decays. No significant excess above the expected background is observed. An upper limit on the branching fraction ℬ( τ → 3 μ ) of 8 . 0 × 10 − 8 at 90% confidence level is obtained, with an expected upper limit of 6 . 9 × 10 − 8 .
Mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles in $$\mathrm {PbPb}$$ collisions at $$\sqrt{\smash [b]{s_{_{\mathrm {NN}}}}} = 2.76$$ and 5.02$$\,\text {Te
Publisher: Springer Science and Business Media LLC
Date: 06-2020
DOI: 10.1140/EPJC/S10052-020-7834-9
Abstract: Anisotropies in the initial energy density distribution of the quark-gluon plasma created in high energy heavy ion collisions lead to anisotropies in the azimuthal distributions of the final-state particles known as collective anisotropic flow. Fourier harmonic decomposition is used to quantify these anisotropies. The higher-order harmonics can be induced by the same order anisotropies (linear response) or by the combined influence of several lower order anisotropies (nonlinear response) in the initial state. The mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles are measured as functions of transverse momentum and centrality in $$\\mathrm {PbPb}$$ PbPb collisions at nucleon-nucleon center-of-mass energies $$\\sqrt{\\smash [b]{s_{_{\\mathrm {NN}}}}} = 2.76$$ s NN = 2.76 and 5.02 $$\\,\\text {TeV}$$ TeV with the CMS detector. The results are compared with viscous hydrodynamic calculations using several different initial conditions, as well as microscopic transport model calculations. None of the models provides a simultaneous description of the mixed higher-order flow harmonics and nonlinear response coefficients.
Search for high-mass resonances decaying to a jet and a Lorentz-boosted resonance in proton-proton collisions at
Publisher:
Elsevier BV
Date:
09-2022
Publisher: Elsevier BV
Date: 09-2022
Search for decays of the 125 GeV Higgs boson into a Z boson and a ρ or ϕ meson
Publisher: Springer Science and Business Media LLC
Date: 11-2020
Abstract: Decays of the 125 GeV Higgs boson into a Z boson and a ρ 0 (770) or ϕ(1020) meson are searched for using proton-proton collision data collected by the CMS experiment at the LHC at $$ \\sqrt{s} $$ s = 13 TeV. The analysed data set corresponds to an integrated luminosity of 137 fb − 1 . Events are selected in which the Z boson decays into a pair of electrons or a pair of muons, and the ρ and ϕ mesons decay into pairs of pions and kaons, respectively. No significant excess above the background model is observed. As different polarization states are possible for the decay products of the Z boson and ρ or ϕ mesons, affecting the signal acceptance, scenarios in which the decays are longitudinally or transversely polarized are considered. Upper limits at the 95% confidence level on the Higgs boson branching fractions into Zρ and Zϕ are determined to be 1.04–1.31% and 0.31–0.40%, respectively, where the ranges reflect the considered polarization scenarios these values are 740–940 and 730–950 times larger than the respective standard model expectations. These results constitute the first experimental limits on the two decay channels.
Dependence of inclusive jet production on the anti-kT distance parameter in pp collisions at $$ \sqrt{\mathrm{s}} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 12-2020
Abstract: The dependence of inclusive jet production in proton-proton collisions with a center-of-mass energy of 13 TeV on the distance parameter R of the anti- k T algorithm is studied using data corresponding to integrated luminosities up to 35.9 fb − 1 collected by the CMS experiment in 2016. The ratios of the inclusive cross sections as functions of transverse momentum p T and rapidity y , for R in the range 0.1 to 1.2 to those using R = 0 . 4 are presented in the region 84 p T 1588 GeV and | y | 2 . 0. The results are compared to calculations at leading and next-to-leading order in the strong coupling constant using different parton shower models. The variation of the ratio of cross sections with R is well described by calculations including a parton shower model, but not by a leading-order quantum chromodynamics calculation including nonperturbative effects. The agreement between the data and the theoretical predictions for the ratios of cross sections is significantly improved when next-to-leading order calculations with nonperturbative effects are used.
Study of central exclusive Equation missing production in proton-proton collisions at $$\sqrt{s} = 5.02$$ and 13TeV
Publisher: Springer Science and Business Media LLC
Date: 08-2020
DOI: 10.1140/EPJC/S10052-020-8166-5
Abstract: Central exclusive and semiexclusive production of "Equation missing" pairs is measured with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of 5.02 and 13TeV. The theoretical description of these nonperturbative processes, which have not yet been measured in detail at the LHC, poses a significant challenge to models. The two pions are measured and identified in the CMS silicon tracker based on specific energy loss, whereas the absence of other particles is ensured by calorimeter information. The total and differential cross sections of exclusive and semiexclusive central "Equation missing" production are measured as functions of invariant mass, transverse momentum, and rapidity of the "Equation missing" system in the fiducial region defined as transverse momentum "Equation missing" and pseudorapidity "Equation missing" . The production cross sections for the four resonant channels "Image missing" , "Equation missing" , "Image missing" , and "Image missing" are extracted using a simple model. These results represent the first measurement of this process at the LHC collision energies of 5.02 and 13TeV.
Search for flavor-changing neutral current interactions of the top quark and the Higgs boson decaying to a bottom quark-antiquark pair at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 02-2022
Abstract: A search for flavor-changing neutral current interactions of the top quark (t) and the Higgs boson (H) is presented. The search is based on a data s le corresponding to an integrated luminosity of 137 fb − 1 recorded by the CMS experiment at the LHC in proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV. Events containing exactly one lepton (muon or electron) and at least three jets, among which at least two are identified as originating from the hadronization of a bottom quark, are analyzed. A set of deep neural networks is used for kinematic event reconstruction, while boosted decision trees distinguish the signal from the background events. No significant excess over the background predictions is observed, and upper limits on the signal production cross sections are extracted. These limits are interpreted in terms of top quark decay branching fractions ( $$ \\mathcal{B} $$ B ) to the Higgs boson and an up (u) or a charm quark (c). Assuming one nonvanishing extra coupling at a time, the observed (expected) upper limits at 95% confidence level are $$ \\mathcal{B} $$ B (t → Hu) 0 . 079 (0 . 11)% and $$ \\mathcal{B} $$ B (t → Hc) 0 . 094 (0 . 086)%.
Search for long-lived particles decaying into muon pairs in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV collected with a dedicated high-rate data stream
Publisher: Springer Science and Business Media LLC
Date: 11-04-2022
Abstract: A search for long-lived particles decaying into muon pairs is performed using proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment at the LHC in 2017 and 2018, corresponding to an integrated luminosity of 101 fb − 1 . The data sets used in this search were collected with a dedicated dimuon trigger stream with low transverse momentum thresholds, recorded at high rate by retaining a reduced amount of information, in order to explore otherwise inaccessible phase space at low dimuon mass and nonzero displacement from the primary interaction vertex. No significant excess of events beyond the standard model expectation is found. Upper limits on branching fractions at 95% confidence level are set on a wide range of mass and lifetime hypotheses in beyond the standard model frameworks with the Higgs boson decaying into a pair of long-lived dark photons, or with a long-lived scalar resonance arising from a decay of a b hadron. The limits are the most stringent to date for substantial regions of the parameter space. These results can be also used to constrain models of displaced dimuons that are not explicitly considered in this paper.
Measurement of the inclusive and differential Higgs boson production cross sections in the leptonic WW decay mode at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 03-2021
Abstract: Measurements of the fiducial inclusive and differential production cross sections of the Higgs boson in proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV are performed using events where the Higgs boson decays into a pair of W bosons that subsequently decay into a final state with an electron, a muon, and a pair of neutrinos. The analysis is based on data collected with the CMS detector at the LHC during 2016–2018, corresponding to an integrated luminosity of 137 fb − 1 . Production cross sections are measured as a function of the transverse momentum of the Higgs boson and the associated jet multiplicity. The Higgs boson signal is extracted and simultaneously unfolded to correct for selection efficiency and resolution effects using maximum-likelihood fits to the observed distributions in data. The integrated fiducial cross section is measured to be 86 . 5 ± 9 . 5 fb, consistent with the Standard Model expectation of 82 . 5 ± 4 . 2 fb. No significant deviation from the Standard Model expectations is observed in the differential measurements.
Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 12-2021
Abstract: A search for new top quark interactions is performed within the framework of an effective field theory using the associated production of either one or two top quarks with a Z boson in multilepton final states. The data s le corresponds to an integrated luminosity of 138 fb − 1 of proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV collected by the CMS experiment at the LHC. Five dimension-six operators modifying the electroweak interactions of the top quark are considered. Novel machine-learning techniques are used to enhance the sensitivity to effects arising from these operators. Distributions used for the signal extraction are parameterized in terms of Wilson coefficients describing the interaction strengths of the operators. All five Wilson coefficients are simultaneously fit to data and 95% confidence level intervals are computed. All results are consistent with the SM expectations.
Observation of tW production in the single-lepton channel in pp collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 11-2021
Abstract: A measurement of the cross section of the associated production of a single top quark and a W boson in final states with a muon or electron and jets in proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV is presented. The data correspond to an integrated luminosity of 36 fb − 1 collected with the CMS detector at the CERN LHC in 2016. A boosted decision tree is used to separate the tW signal from the dominant t $$ \\overline{\\mathrm{t}} $$ t ¯ background, whilst the subleading W+jets and multijet backgrounds are constrained using data-based estimates. This result is the first observation of the tW process in final states containing a muon or electron and jets, with a significance exceeding 5 standard deviations. The cross section is determined to be 89 ± 4 (stat) ± 12 (syst) pb, consistent with the standard model.
Performance of the reconstruction and identification of high-momentum muons in proton-proton collisions at √s = 13 TeV
Publisher: IOP Publishing
Date: 28-02-2020
Measurement of the
W γ
Publisher: American Physical Society (APS)
Date: 25-06-2021
Strange hadron production in
pp p <
Publisher: American Physical Society (APS)
Date: 22-06-2020
Evidence for WW/WZ vector boson scattering in the decay channel ℓνqq produced in association with two jets in proton-proton collisions at
Publisher:
Elsevier BV
Date:
11-2022
Publisher: Elsevier BV
Date: 11-2022
Observation of a New Excited Beauty Strange Baryon Decaying to
Ξ b<
Publisher: American Physical Society (APS)
Date: 25-06-2021
Using
Z
Publisher: American Physical Society (APS)
Date: 23-03-2022
Measurement of the CP-violating phase ϕs in the B
Publisher:
Elsevier BV
Date:
05-2021
Publisher: Elsevier BV
Date: 05-2021
Measurements of the associated production of a W boson and a charm quark in proton–proton collisions at $$\sqrt{s}=8\,\text {TeV} $$
Publisher: Springer Science and Business Media LLC
Date: 05-12-2022
DOI: 10.1140/EPJC/S10052-022-10897-7
Abstract: Measurements of the associated production of a W boson and a charm ( $${\\text {c}}$$ c ) quark in proton–proton collisions at a centre-of-mass energy of 8 $$\\,\\text {TeV}$$ TeV are reported. The analysis uses a data s le corresponding to a total integrated luminosity of 19.7 $$\\,\\text {fb}^{-1}$$ fb - 1 collected by the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm quark jets are selected using distinctive signatures of charm hadron decays. The product of the cross section and branching fraction $$\\sigma (\\text {p}\\text {p}\\rightarrow \\text {W}+ {\\text {c}}+ \\text {X}) {\\mathcal {B}}(\\text {W}\\rightarrow \\ell \\upnu )$$ σ ( pp → W + c + X ) B ( W → ℓ ν ) , where $$\\ell = \\text {e}$$ ℓ = e or $$\\upmu $$ μ , and the cross section ratio $$\\sigma (\\text {p}\\text {p}\\rightarrow {{\\text {W}}^{+} + \\bar{{\\text {c}}} + \\text {X}}) / \\sigma (\\text {p}\\text {p}\\rightarrow {{\\text {W}}^{-} + {\\text {c}}+ \\text {X}})$$ σ ( pp → W + + c ¯ + X ) / σ ( pp → W - + c + X ) are measured in a fiducial volume and differentially as functions of the pseudorapidity and of the transverse momentum of the lepton from the W boson decay. The results are compared with theoretical predictions. The impact of these measurements on the determination of the strange quark distribution is assessed.
Nuclear modification of Y states in pPb collisions at s
Publisher:
Elsevier BV
Date:
12-2022
Publisher: Elsevier BV
Date: 12-2022
Measurement of the cross section for electroweak production of a Z boson, a photon and two jets in proton-proton collisions at $$ \sqrt{\mathrm{s}} $$ = 13 TeV and constraints on anomalous quartic cou
Publisher: Springer Science and Business Media LLC
Date: 06-2020
Study of Z boson plus jets events using variables sensitive to double-parton scattering in pp collisions at 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 10-2021
Abstract: Double-parton scattering is investigated using events with a Z boson and jets. The Z boson is reconstructed using only the dimuon channel. The measurements are performed with proton-proton collision data recorded by the CMS experiment at the LHC at $$ \sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb − 1 collected in the year 2016. Differential cross sections of Z+ ≥ 1 jet and Z+ ≥ 2 jets are measured with transverse momentum of the jets above 20 GeV and pseudorapidity |η| 2 . 4. Several distributions with sensitivity to double-parton scattering effects are measured as functions of the angle and the transverse momentum imbalance between the Z boson and the jets. The measured distributions are compared with predictions from several event generators with different hadronization models and different parameter settings for multiparton interactions. The measured distributions show a dependence on the hadronization and multiparton interaction simulation parameters, and are important input for future improvements of the simulations.
Measurements of the pp → W±γγ and pp → Zγγ cross sections at $$ \sqrt{\mathrm{s}} $$ = 13 TeV and limits on anomalous quartic gauge couplings
Publisher: Springer Science and Business Media LLC
Date: 10-2021
Abstract: The cross section for W or Z boson production in association with two photons is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data set corresponds to an integrated luminosity of 137 fb − 1 collected by the CMS experiment at the LHC. The W → ℓν and Z → ℓℓ decay modes (where ℓ = e , μ ) are used to extract the W γγ and Z γγ cross sections in a phase space defined by electron (muon) with transverse momentum larger than 30 GeV and photon transverse momentum larger than 20 GeV. All leptons and photons are required to have absolute pseudorapidity smaller than 2.5. The measured cross sections in this phase space are σ (W γγ ) = $$ {13.6}_{-1.9}^{+1.9}{\\left(\\mathrm{stat}\\right)}_{-4.0}^{+4.0} $$ 13.6 − 1.9 + 1.9 stat − 4.0 + 4.0 (syst) ± 0 . 08 (PDF + scale) fb and σ (Z γγ ) = $$ {5.41}_{-0.55}^{+0.58}{\\left(\\mathrm{stat}\\right)}_{-.070}^{+0.64} $$ 5.41 − 0.55 + 0.58 stat − .070 + 0.64 (syst) ± 0 . 06 (PDF + scale) fb. Limits on anomalous quartic gauge couplings are set in the framework of an effective field theory with dimension-8 operators.
Search for long-lived particles produced in association with a Z boson in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 03-2022
Abstract: A search for long-lived particles (LLPs) produced in association with a Z boson is presented. The study is performed using data from proton-proton collisions with a center-of-mass energy of 13 TeV recorded by the CMS experiment during 2016–2018, corresponding to an integrated luminosity of 117 fb − 1 . The LLPs are assumed to decay to a pair of standard model quarks that are identified as displaced jets within the CMS tracker system. Triggers and selections based on Z boson decays to electron or muon pairs improve the sensitivity to light LLPs (down to 15 GeV). This search provides sensitivity to beyond the standard model scenarios which predict LLPs produced in association with a Z boson. In particular, the results are interpreted in the context of exotic decays of the Higgs boson to a pair of scalar LLPs (H → SS). The Higgs boson decay branching fraction is constrained to values less than 6% for proper decay lengths of 10–100 mm and for LLP masses between 40 and 55 GeV. In the case of low-mass ( ≈ 15 GeV) scalar particles that subsequently decay to a pair of b quarks, the search is sensitive to branching fractions $$ \\mathcal{B} $$ B (H → SS) 20% for proper decay lengths of 10–50 mm. The use of associated production with a Z boson increases the sensitivity to low-mass LLPs of this analysis with respect to gluon fusion searches. In the case of 15 GeV scalar LLPs, the improvement corresponds to a factor of 2 at a proper decay length of 30 mm.
Measurements of the differential cross sections of the production of Z + jets and γ + jets and of Z boson emission collinear with a jet in pp collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 05-2021
Abstract: Measurements of the differential cross sections of Z + jets and γ + jets production, and their ratio, are presented as a function of the boson transverse momentum. Measurements are also presented of the angular distribution between the Z boson and the closest jet. The analysis is based on pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 35.9 fb − 1 recorded by the CMS experiment at the LHC. The results, corrected for detector effects, are compared with various theoretical predictions. In general, the predictions at higher orders in perturbation theory show better agreement with the measurements. This work provides the first measurement of the ratio of the differential cross sections of Z + jets and γ + jets production at 13 TeV, as well as the first direct measurement of Z bosons emitted collinearly with a jet.
First measurement of large area jet transverse momentum spectra in heavy-ion collisions
Publisher: Springer Science and Business Media LLC
Date: 05-2021
Abstract: Jet production in lead-lead (PbPb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV is studied with the CMS detector at the LHC, using PbPb and pp data s les corresponding to integrated luminosities of 404 μ b − 1 and 27.4 pb − 1 , respectively. Jets with different areas are reconstructed using the anti- k T algorithm by varying the distance parameter R . The measurements are performed using jets with transverse momenta ( p T ) greater than 200 GeV and in a pseudorapidity range of |η| 2. To reveal the medium modification of the jet spectra in PbPb collisions, the properly normalized ratio of spectra from PbPb and pp data is used to extract jet nuclear modification factors as functions of the PbPb collision centrality, p T and, for the first time, as a function of R up to 1.0. For the most central collisions, a strong suppression is observed for high- p T jets reconstructed with all distance parameters, implying that a significant amount of jet energy is scattered to large angles. The dependence of jet suppression on R is expected to be sensitive to both the jet energy loss mechanism and the medium response, and so the data are compared to several modern event generators and analytic calculations. The models considered do not fully reproduce the data.
Probing Charm Quark Dynamics via Multiparticle Correlations in Pb-Pb Collisions at
<
Publisher: American Physical Society (APS)
Date: 05-07-2022
Search for heavy resonances decaying to a pair of Lorentz-boosted Higgs bosons in final states with leptons and a bottom quark pair at $$ \sqrt{s} $$= 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 02-05-2012
Abstract: A search for new heavy resonances decaying to a pair of Higgs bosons (HH) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. Data were collected with the CMS detector at the LHC in 2016–2018, corresponding to an integrated luminosity of 138 fb − 1 . Resonances with a mass between 0.8 and 4.5 TeV are considered using events in which one Higgs boson decays into a bottom quark pair and the other into final states with either one or two charged leptons. Specifically, the single-lepton decay channel $$ \\mathrm{HH}\\to \\mathrm{b}\\overline{\\mathrm{b}}{\\mathrm{WW}}^{\\ast}\\to \\mathrm{b}\\overline{\\mathrm{b}}\\ell v\\mathrm{q}{\\overline{\\mathrm{q}}}^{\\prime } $$ HH → b b ¯ WW ∗ → b b ¯ ℓ v q q ¯ ′ and the dilepton decay channels $$ \\mathrm{HH}\\to \\mathrm{b}\\overline{\\mathrm{b}}{\\mathrm{WW}}^{\\ast}\\to \\mathrm{b}\\overline{\\mathrm{b}}\\ell v\\ell v $$ HH → b b ¯ WW ∗ → b b ¯ ℓ v ℓ v and $$ \\mathrm{HH}\\to \\mathrm{b}\\overline{\\mathrm{b}}\\uptau \\uptau \\to \\mathrm{b}\\overline{\\mathrm{b}}\\ell vv\\ell vv $$ HH → b b ¯ ττ → b b ¯ ℓ vv ℓ vv are examined, where ℓ in the final state corresponds to an electron or muon. The signal is extracted using a two-dimensional maximum likelihood fit of the $$ \\mathrm{H}\\to \\mathrm{b}\\overline{\\mathrm{b}} $$ H → b b ¯ jet mass and HH invariant mass distributions. No significant excess above the standard model expectation is observed in data. Model-independent exclusion limits are placed on the product of the cross section and branching fraction for narrow spin-0 and spin-2 massive bosons decaying to HH. The results are also interpreted in the context of radion and bulk graviton production in models with a warped extra spatial dimension. The results provide the most stringent limits to date for X → HH signatures with final-state leptons and at some masses provide the most sensitive limits of all X → HH searches.
Observation of the
B s
Publisher:
American Physical Society (APS)
Date:
07-10-2020
Publisher: American Physical Society (APS)
Date: 07-10-2020
Identification of heavy, energetic, hadronically decaying particles using machine-learning techniques
Publisher: IOP Publishing
Date: 03-06-2020
Measurement of the Z boson differential production cross section using its invisible decay mode (Z → $$ \nu \overline{\nu} $$) in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 05-2021
Abstract: Measurements of the total and differential fiducial cross sections for the Z boson decaying into two neutrinos are presented at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were collected by the CMS detector in 2016 and correspond to an integrated luminosity of 35.9 fb − 1 . In these measurements, events are selected containing an imbalance in transverse momentum and one or more energetic jets. The fiducial differential cross section is measured as a function of the Z boson transverse momentum. The results are combined with a previous measurement of charged-lepton decays of the Z boson. The measured total fiducial cross section for events with Z boson transverse momentum greater than 200 GeV is $$ {3000}_{-170}^{+180} $$ 3000 − 170 + 180 fb.
A new calibration method for charm jet identification validated with proton-proton collision events at √s = 13 TeV
Publisher: IOP Publishing
Date: 03-2022
DOI: 10.1088/1748-0221/17/03/P03014
Abstract: Many measurements at the LHC require efficient identification of heavy-flavour jets, i.e. jets originating from bottom (b) or charm (c) quarks. An overview of the algorithms used to identify c jets is described and a novel method to calibrate them is presented. This new method adjusts the entire distributions of the outputs obtained when the algorithms are applied to jets of different flavours. It is based on an iterative approach exploiting three distinct control regions that are enriched with either b jets, c jets, or light-flavour and gluon jets. Results are presented in the form of correction factors evaluated using proton-proton collision data with an integrated luminosity of 41.5 fb -1 at √s = 13 TeV, collected by the CMS experiment in 2017. The closure of the method is tested by applying the measured correction factors on simulated data sets and checking the agreement between the adjusted simulation and collision data. Furthermore, a validation is performed by testing the method on pseudodata, which emulate various mismodelling conditions. The calibrated results enable the use of the full distributions of heavy-flavour identification algorithm outputs, e.g. as inputs to machine-learning models. Thus, they are expected to increase the sensitivity of future physics analyses.
Measurements with silicon photomultipliers of dose-rate effects in the radiation damage of plastic scintillator tiles in the CMS hadron endcap calorimeter
Publisher: IOP Publishing
Date: 08-06-2020
DOI: 10.1088/1748-0221/15/06/P06009
Abstract: Measurements are presented of the reduction of signal output due to radiation damage for two types of plastic scintillator tiles used in the hadron endcap (HE) calorimeter of the CMS detector. The tiles were exposed to particles produced in proton-proton (pp) collisions at the CERN LHC with a center-of-mass energy of 13 TeV, corresponding to a delivered luminosity of 50 fb −1 . The measurements are based on readout channels of the HE that were instrumented with silicon photomultipliers, and are derived using data from several sources: a laser calibration system, a movable radioactive source, as well as hadrons and muons produced in pp collisions. Results from several irradiation c aigns using 60 Co sources are also discussed. The damage is presented as a function of dose rate. Within the range of these measurements, for a fixed dose the damage increases with decreasing dose rate.
Search for single production of a vector-like T quark decaying to a top quark and a Z boson in the final state with jets and missing transverse momentum at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 16-05-2022
Abstract: A search is presented for single production of a vector-like T quark with charge 2 / 3 e , in the decay channel featuring a top quark and a Z boson, with the top quark decaying hadronically and the Z boson decaying to neutrinos. The search uses data collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb − 1 recorded at the CERN LHC in 2016–2018. The search is sensitive to a T quark mass between 0.6 and 1.8 TeV with decay widths ranging from negligibly small up to 30% of the T quark mass. Reconstruction strategies for the top quark are based on the degree of Lorentz boosting of its final state. At 95% confidence level, the upper limit on the product of the cross section and branching fraction for a T quark of small decay width varies between 15 and 602 fb, depending on its mass. For a T quark with decay widths between 10 and 30% of its mass, this upper limit ranges between 16 and 836 fb. For most of the studied range, the results provide the best limits to date. This is the first search for single T quark production based on the full Run 2 data set of the LHC.
Angular analysis of the decay B+ → K∗(892)+μ+μ− in proton-proton collisions at $$ \sqrt{\mathrm{s}} $$ = 8 TeV
Publisher: Springer Science and Business Media LLC
Date: 04-2021
Abstract: Angular distributions of the decay B + → K ∗ (892) + μ + μ − are studied using events collected with the CMS detector in $$ \\sqrt{\\mathrm{s}} $$ s = 8 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 20.0 fb − 1 . The forward-backward asymmetry of the muons and the longitudinal polarization of the K ∗ (892) + meson are determined as a function of the square of the dimuon invariant mass. These are the first results from this exclusive decay mode and are in agreement with a standard model prediction.
Strategies and performance of the CMS silicon tracker alignment during LHC Run 2
Publisher: Elsevier BV
Date: 08-2022
Search for long-lived particles using displaced jets in proton-proton collisions at
s<
Publisher: American Physical Society (APS)
Date: 30-07-2021
Measurement of the inclusive and differential t$$ \overline{t} $$γ cross sections in the dilepton channel and effective field theory interpretation in proton-proton collisions at $$ \sqrt{s} $$ = 13 T
Publisher: Springer Science and Business Media LLC
Date: 16-05-2022
Abstract: The production cross section of a top quark pair in association with a photon is measured in proton-proton collisions in the decay channel with two oppositely charged leptons ( e ± μ ∓ , e + e − , or μ + μ − ). The measurement is performed using 138 fb − 1 of proton-proton collision data recorded by the CMS experiment at $$ \\sqrt{s} $$ s = 13 TeV during the 2016–2018 data-taking period of the CERN LHC. A fiducial phase space is defined such that photons radiated by initial-state particles, top quarks, or any of their decay products are included. An inclusive cross section of 175 . 2 ± 2 . 5(stat) ± 6 . 3(syst) fb is measured in a signal region with at least one jet coming from the hadronization of a bottom quark and exactly one photon with transverse momentum above 20 GeV. Differential cross sections are measured as functions of several kinematic observables of the photon, leptons, and jets, and compared to standard model predictions. The measurements are also interpreted in the standard model effective field theory framework, and limits are found on the relevant Wilson coefficients from these results alone and in combination with a previous CMS measurement of the t $$ \\overline{t} $$ t ¯ γ production process using the lepton+jets final state.
Search for an excited lepton that decays via a contact interaction to a lepton and two jets in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 05-2020
Measurement of the Higgs boson width and evidence of its off-shell contributions to ZZ production
Publisher: Springer Science and Business Media LLC
Date: 20-10-2022
DOI: 10.1038/S41567-022-01682-0
Abstract: Since the discovery of the Higgs boson in 2012, detailed studies of its properties have been ongoing. Besides its mass, its width—related to its lifetime—is an important parameter. One way to determine this quantity is to measure its off-shell production, where the Higgs boson mass is far away from its nominal value, and relating it to its on-shell production, where the mass is close to the nominal value. Here we report evidence for such off-shell contributions to the production cross-section of two Z bosons with data from the CMS experiment at the CERN Large Hadron Collider. We constrain the total rate of the off-shell Higgs boson contribution beyond the Z boson pair production threshold, relative to its standard model expectation, to the interval [0.0061, 2.0] at the 95% confidence level. The scenario with no off-shell contribution is excluded at a p -value of 0.0003 (3.6 standard deviations). We measure the width of the Higgs boson as $${{{\\varGamma }}}_{{{{{{\\rm{H}}}}}}}={3.2}_{-1.7}^{+2.4}\\,{{{{{\\rm{MeV}}}}}}$$ Γ H = 3.2 − 1.7 + 2.4 MeV , in agreement with the standard model expectation of 4.1 MeV. In addition, we set constraints on anomalous Higgs boson couplings to W and Z boson pairs.
Search for heavy Higgs bosons decaying to a top quark pair in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 04-2020
Search for new particles in an extended Higgs sector with four b quarks in the final state at s
Publisher:
Elsevier BV
Date:
12-2022
Publisher: Elsevier BV
Date: 12-2022
Search for chargino-neutralino production in events with Higgs and W bosons using 137 fb−1 of proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 10-2021
Abstract: A search for electroweak production of supersymmetric (SUSY) particles in final states with one lepton, a Higgs boson decaying to a pair of bottom quarks, and large missing transverse momentum is presented. The search uses data from proton-proton collisions at a center-of-mass energy of 13 TeV collected using the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb − 1 . The observed yields are consistent with backgrounds expected from the standard model. The results are interpreted in the context of a simplified SUSY model of chargino-neutralino production, with the chargino decaying to a W boson and the lightest SUSY particle (LSP) and the neutralino decaying to a Higgs boson and the LSP. Charginos and neutralinos with masses up to 820 GeV are excluded at 95% confidence level when the LSP mass is small, and LSPs with mass up to 350 GeV are excluded when the masses of the chargino and neutralino are approximately 700 GeV.
Analysis of the CP structure of the Yukawa coupling between the Higgs boson and τ leptons in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 03-06-2022
Abstract: The first measurement of the CP structure of the Yukawa coupling between the Higgs boson and τ leptons is presented. The measurement is based on data collected in proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb − 1 . The analysis uses the angular correlation between the decay planes of τ leptons produced in Higgs boson decays. The effective mixing angle between CP -even and CP -odd τ Yukawa couplings is found to be − 1 ± 19°, compared to an expected value of 0 ± 21° at the 68.3% confidence level. The data disfavour the pure CP -odd scenario at 3.0 standard deviations. The results are compatible with predictions for the standard model Higgs boson.
Reconstruction of signal amplitudes in the CMS electromagnetic calorimeter in the presence of overlapping proton-proton interactions
Publisher: IOP Publishing
Date: 10-2020
Combined search for supersymmetry with photons in proton-proton collisions at s
Publisher:
Elsevier BV
Date:
02-2020
Publisher: Elsevier BV
Date: 02-2020
Search for supersymmetry in final states with two oppositely charged same-flavor leptons and missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 04-2021
Abstract: A search for phenomena beyond the standard model in final states with two oppositely charged same-flavor leptons and missing transverse momentum is presented. The search uses a data s le of proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 137 fb − 1 , collected by the CMS experiment at the LHC. Three potential signatures of physics beyond the standard model are explored: an excess of events with a lepton pair, whose invariant mass is consistent with the Z boson mass a kinematic edge in the invariant mass distribution of the lepton pair and the nonresonant production of two leptons. The observed event yields are consistent with those expected from standard model backgrounds. The results of the first search allow the exclusion of gluino masses up to 1870 GeV, as well as chargino (neutralino) masses up to 750 (800) GeV, while those of the searches for the other two signatures allow the exclusion of light-flavor (bottom) squark masses up to 1800 (1600) GeV and slepton masses up to 700 GeV, respectively, at 95% confidence level within certain supersymmetry scenarios.
Measurement of quark- and gluon-like jet fractions using jet charge in PbPb and pp collisions at 5.02 TeV
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Abstract: The momentum-weighted sum of the electric charges of particles inside a jet, known as jet charge, is sensitive to the electric charge of the particle initiating the parton shower. This paper presents jet charge distributions in $$ \\sqrt{s_{\\mathrm{NN}}} $$ s NN = 5 . 02 TeV lead-lead (PbPb) and proton-proton (pp) collisions recorded with the CMS detector at the LHC. These data correspond to integrated luminosities of 404 μ b − 1 and 27.4 pb − 1 for PbPb and pp collisions, respectively. Leveraging the sensitivity of the jet charge to fundamental differences in the electric charges of quarks and gluons, the jet charge distributions from simulated events are used as templates to extract the quark- and gluon-like jet fractions from data. The modification of these jet fractions is examined by comparing pp and PbPb data as a function of the overlap of the colliding Pb nuclei (centrality). This measurement tests the color charge dependence of jet energy loss due to interactions with the quark-gluon plasma. No significant modification between different centrality classes and with respect to pp results is observed in the extracted quark- and gluon-like jet fractions.
The production of isolated photons in PbPb and pp collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Abstract: The transverse energy ( $$ {E}_{\mathrm{T}}^{\upgamma} $$ E T γ ) spectra of photons isolated from other particles are measured using proton-proton (pp) and lead-lead (PbPb) collisions at the LHC at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5 . 02 TeV with integrated luminosities of 27.4 pb − 1 and 404 μ b − 1 for pp and PbPb data, respectively. The results are presented for photons with 25 $$ {E}_{\mathrm{T}}^{\upgamma} $$ E T γ 200 GeV in the pseudorapidity range |η| 1 . 44, and for different centrality intervals for PbPb collisions. Photon production in PbPb collisions is consistent with that in pp collisions scaled by the number of binary nucleon-nucleon collisions, demonstrating that photons do not interact with the quark-gluon plasma. Therefore, isolated photons can provide information about the initial energy of the associated parton in photon+jet measurements. The results are compared with predictions from the next-to-leading-order jetphox generator for different parton distribution functions (PDFs) and nuclear PDFs (nPDFs). The comparisons can help to constrain the nPDFs global fits.
Search for heavy resonances decaying to ZZ or ZW and axion-like particles mediating nonresonant ZZ or ZH production at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 14-04-2022
Abstract: A search has been performed for heavy resonances decaying to ZZ or ZW and for axion-like particles (ALPs) mediating nonresonant ZZ or ZH production, in final states with two charged leptons ( ℓ = e , μ) produced by the decay of a Z boson, and two quarks produced by the decay of a Z, W, or Higgs boson H. The analysis is sensitive to resonances with masses in the range 450 to 2000 GeV. Two categories are defined corresponding to the merged or resolved reconstruction of the hadronically decaying boson. The search is based on data collected during 2016–2018 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb − 1 . No significant excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-2 and spin-1 resonances are derived as functions of the resonance mass, and exclusion limits on the production of bulk graviton particles and W′ bosons are calculated in the framework of the warped extra dimensions and heavy vector triplet models, respectively. In addition, upper limits on the ALP-mediated diboson production cross section and ALP couplings to standard model particles are obtained in the framework of linear and chiral effective field theories. These are the first limits on nonresonant ALP-mediated ZZ and ZH production obtained by the LHC experiments.
Search for a heavy resonance decaying to a top quark and a W boson at $$ \sqrt{s} $$ = 13 TeV in the fully hadronic final state
Publisher: Springer Science and Business Media LLC
Date: 12-2021
Abstract: A search for a heavy resonance decaying to a top quark and a W boson in the fully hadronic final state is presented. The analysis is performed using data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb − 1 recorded by the CMS experiment at the LHC. The search is focused on heavy resonances, where the decay products of each top quark or W boson are expected to be reconstructed as a single, large-radius jet with a distinct substructure. The production of an excited bottom quark, b * , is used as a benchmark when setting limits on the cross section for a heavy resonance decaying to a top quark and a W boson. The hypotheses of b * quarks with left-handed, right-handed, and vector-like chiralities are excluded at 95% confidence level for masses below 2.6, 2.8, and 3.1 TeV, respectively. These are the most stringent limits on the b * quark mass to date, extending the previous best limits by almost a factor of two.
Hard color-singlet exchange in dijet events in proton-proton collisions at
s =
Publisher: American Physical Society (APS)
Date: 26-08-2021
Observation of electroweak production of Wγ with two jets in proton-proton collisions at s
Publisher:
Elsevier BV
Date:
12-2020
Publisher: Elsevier BV
Date: 12-2020
Measurement of the inclusive and differential t$$ \overline{t} $$γ cross sections in the single-lepton channel and EFT interpretation at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 12-2021
Abstract: The production cross section of a top quark pair in association with a photon is measured in proton-proton collisions at a center-of-mass energy of 13 TeV. The data set, corresponding to an integrated luminosity of 137 fb − 1 , was recorded by the CMS experiment during the 2016–2018 data taking of the LHC. The measurements are performed in a fiducial volume defined at the particle level. Events with an isolated, highly energetic lepton, at least three jets from the hadronization of quarks, among which at least one is b tagged, and one isolated photon are selected. The inclusive fiducial t $$ \overline{\mathrm{t}} $$ t ¯ γ cross section, for a photon with transverse momentum greater than 20 GeV and pseudorapidity |η| 1 . 4442, is measured to be 798 ± 7(stat) ± 48(syst) fb, in good agreement with the prediction from the standard model at next-to-leading order in quantum chromodynamics. The differential cross sections are also measured as a function of several kinematic observables and interpreted in the framework of the standard model effective field theory (EFT), leading to the most stringent direct limits to date on anomalous electromagnetic dipole moment interactions of the top quark and the photon.
Search for disappearing tracks in proton-proton collisions at s
Publisher:
Elsevier BV
Date:
07-2020
Publisher: Elsevier BV
Date: 07-2020
Combination of the W boson polarization measurements in top quark decays using ATLAS and CMS data at $$ \sqrt{s} $$ = 8 TeV
Publisher: Springer Science and Business Media LLC
Date: 08-2020
Abstract: The combination of measurements of the W boson polarization in top quark decays performed by the ATLAS and CMS collaborations is presented. The measurements are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of about 20 fb − 1 for each experiment. The measurements used events containing one lepton and having different jet multiplicities in the final state. The results are quoted as fractions of W bosons with longitudinal ( F 0 ), left-handed ( F L ), or right-handed ( F R ) polarizations. The resulting combined measurements of the polarization fractions are F 0 = 0 . 693 ± 0 . 014 and F L = 0 . 315 ± 0 . 011. The fraction F R is calculated from the unitarity constraint to be F R = − 0 . 008 ± 0 . 007. These results are in agreement with the standard model predictions at next-to-next-to-leading order in perturbative quantum chromodynamics and represent an improvement in precision of 25 (29)% for F 0 ( F L ) with respect to the most precise single measurement. A limit on anomalous right-handed vector ( V R ), and left- and right-handed tensor ( g L , g R ) tWb couplings is set while fixing all others to their standard model values. The allowed regions are [ − 0 . 11 , 0 . 16] for V R , [ − 0 . 08 , 0 . 05] for g L , and [ − 0 . 04 , 0 . 02] for g R , at 95% confidence level. Limits on the corresponding Wilson coefficients are also derived.
Search for Flavor-Changing Neutral Current Interactions of the Top Quark and Higgs Boson in Final States with Two Photons in Proton-Proton Collisions at
Publisher:
American Physical Society (APS)
Date:
13-07-2022
Publisher: American Physical Society (APS)
Date: 13-07-2022
Performance of the CMS Level-1 trigger in proton-proton collisions at √s = 13 TeV
Publisher: IOP Publishing
Date: 19-10-2020
Evidence for X(3872) in Pb-Pb Collisions and Studies of its Prompt Production at
s
Publisher:
American Physical Society (APS)
Date:
19-01-2022
Publisher: American Physical Society (APS)
Date: 19-01-2022
The very forward CASTOR calorimeter of the CMS experiment
Publisher: IOP Publishing
Date: 08-02-2021
Search for Wγ resonances in proton-proton collisions at s
Publisher:
Elsevier BV
Date:
03-2022
Publisher: Elsevier BV
Date: 03-2022
Measurement of the Drell-Yan forward-backward asymmetry at high dilepton masses in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 04-08-2022
Abstract: A measurement of the forward-backward asymmetry of pairs of oppositely charged leptons (dimuons and dielectrons) produced by the Drell-Yan process in proton-proton collisions is presented. The data s le corresponds to an integrated luminosity of 138 fb − 1 collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV. The asymmetry is measured as a function of lepton pair mass for masses larger than 170 GeV and compared with standard model predictions. An inclusive measurement across both channels and the full mass range yields an asymmetry of 0 . 612 ± 0 . 005 (stat) ± 0 . 007 (syst). As a test of lepton flavor universality, the difference between the dimuon and dielectron asymmetries is measured as well. No statistically significant deviations from standard model predictions are observed. The measurements are used to set limits on the presence of additional gauge bosons. For a Z′ boson in the sequential standard model the observed (expected) 95% confidence level lower limit on the Z′ mass is 4.4 TeV (3.7 TeV).
Observation of the
B c
Publisher:
American Physical Society (APS)
Date:
21-06-2022
Publisher: American Physical Society (APS)
Date: 21-06-2022
Study of dijet events with large rapidity separation in proton-proton collisions at $$ \sqrt{s} $$ = 2.76 TeV
Publisher: Springer Science and Business Media LLC
Date: 03-2022
Abstract: The cross sections for inclusive and Mueller-Navelet dijet production are measured as a function of the rapidity separation between the jets in proton-proton collisions at $$ \sqrt{s} $$ s = 2 . 76 TeV for jets with transverse momentum p T 35 GeV and rapidity | y | 4 . 7. Various dijet production cross section ratios are also measured. A veto on additional jets with p T 20 GeV is introduced to improve the sensitivity to the effects of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution. The measurement is compared with the predictions of various Monte Carlo models based on leading-order and next-to-leading-order calculations including the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi leading-logarithm (LL) parton shower as well as the LL BFKL resummation.
Evidence for electroweak production of four charged leptons and two jets in proton-proton collisions at <
Publisher: Elsevier BV
Date: 2021
Observation of Forward Neutron Multiplicity Dependence of Dimuon Acoplanarity in Ultraperipheral Pb-Pb Collisions at
Publisher:
American Physical Society (APS)
Date:
17-09-2021
Publisher: American Physical Society (APS)
Date: 17-09-2021
Search for supersymmetry in final states with two or three soft leptons and missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 14-04-2022
Abstract: A search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed. The search uses proton-proton collisions at $$ \\sqrt{s} $$ s = 13 TeV collected in the three-year period 2016–2018 by the CMS experiment at the LHC and corresponding to an integrated luminosity of up to 137 fb − 1 . The data are found to be in agreement with expectations from standard model processes. The results are interpreted in terms of electroweakino and top squark pair production with a small mass difference between the produced supersymmetric particles and the lightest neutralino. For the electroweakino interpretation, two simplified models are used, a wino-bino model and a higgsino model. Exclusion limits at 95% confidence level are set on $$ {\\overset{\\sim }{\\upchi}}_2^0/{\\overset{\\sim }{\\upchi}}_1^{\\pm } $$ χ ~ 2 0 / χ ~ 1 ± masses up to 275 GeV for a mass difference of 10 GeV in the wino-bino case, and up to 205(150) GeV for a mass difference of 7.5 (3) GeV in the higgsino case. The results for the higgsino are further interpreted using a phenomenological minimal supersymmetric standard model, excluding the higgsino mass parameter μ up to 180 GeV with the bino mass parameter M 1 at 800 GeV. In the top squark interpretation, exclusion limits are set at top squark masses up to 540 GeV for four-body top squark decays and up to 480 GeV for chargino-mediated decays with a mass difference of 30 GeV.
Measurement of the Jet Mass Distribution and Top Quark Mass in Hadronic Decays of Boosted Top Quarks in
p
Publisher:
American Physical Society (APS)
Date:
21-05-2020
Publisher: American Physical Society (APS)
Date: 21-05-2020
Investigation into the event-activity dependence of ϒ(nS) relative production in proton-proton collisions at $$ \sqrt{s} $$ = 7 TeV
Publisher: Springer Science and Business Media LLC
Date: 11-2020
Abstract: The ratios of the production cross sections between the excited ϒ(2S) and ϒ(3S) mesons and the ϒ(1S) ground state, detected via their decay into two muons, are studied as a function of the number of charged particles in the event. The data are from proton-proton collisions at $$ \\sqrt{s} $$ s = 7 TeV, corresponding to an integrated luminosity of 4.8 fb − 1 , collected with the CMS detector at the LHC. Evidence of a decrease in these ratios as a function of the particle multiplicity is observed, more pronounced at low transverse momentum $$ {p}_{\\mathrm{T}}^{\\upmu \\upmu} $$ p T μμ . For ϒ(nS) mesons with $$ {p}_{\\mathrm{T}}^{\\upmu \\upmu} $$ p T μμ 7 GeV, where most of the data were collected, the correlation with multiplicity is studied as a function of the underlying event transverse sphericity and the number of particles in a cone around the ϒ(nS) direction. The ratios are found to be multiplicity independent for jet-like events. The mean $$ {p}_{\\mathrm{T}}^{\\upmu \\upmu} $$ p T μμ values for the ϒ(nS) states as a function of particle multiplicity are also measured and found to grow more steeply as their mass increases.
Search for resonances decaying to three
W
Publisher: American Physical Society (APS)
Date: 06-07-2022
Search for lepton-flavor violating decays of the Higgs boson in the
μ τ
Publisher:
American Physical Society (APS)
Date:
31-08-2021
Publisher: American Physical Society (APS)
Date: 31-08-2021
Search for charged Higgs bosons decaying into a top and a bottom quark in the all-jet final state of pp collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Abstract: A search for charged Higgs bosons (H ± ) decaying into a top and a bottom quark in the all-jet final state is presented. The analysis uses LHC proton-proton collision data recorded with the CMS detector in 2016 at $$ \\sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb − 1 . No significant excess is observed above the expected background. Model-independent upper limits at 95% confidence level are set on the product of the H ± production cross section and branching fraction in two scenarios. For production in association with a top quark, limits of 21.3 to 0.007 pb are obtained for H ± masses in the range of 0.2 to 3 TeV. Combining this with a search in leptonic final states results in improved limits of 9.25 to 0.005 pb. The complementary s -channel production of an H ± is investigated in the mass range of 0.8 to 3 TeV and the corresponding upper limits are 4.5 to 0.023 pb. These results are interpreted using different minimal supersymmetric extensions of the standard model.
Measurement of the cross section for $$ \mathrm{t}\overline{\mathrm{t}} $$ production with additional jets and b jets in pp collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Abstract: Measurements of the cross section for the production of top quark pairs in association with a pair of jets from bottom quarks $$ \\left({\\sigma}_{\\mathrm{t}\\overline{\\mathrm{t}}\\mathrm{b}\\overline{\\mathrm{b}}}\\right) $$ σ t t ¯ b b ¯ and in association with a pair of jets from quarks of any flavor or gluons $$ \\left({\\sigma}_{\\mathrm{t}\\overline{\\mathrm{t}}\\mathrm{jj}}\\right) $$ σ t t ¯ jj and their ratio are presented. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.9 fb − 1 . The measurements are performed in a fiducial phase space and extrapolated to the full phase space, separately for the dilepton and lepton+jets channels, where lepton corresponds to either an electron or a muon. The results of the measurements in the fiducial phase space for the dilepton and lepton+jets channels, respectively, are $$ {\\sigma}_{\\mathrm{t}\\overline{\\mathrm{t}}\\mathrm{jj}} $$ σ t t ¯ jj = 2 . 36 ± 0 . 02 (stat) ± 0 . 20 (syst) pb and 31 . 0 ± 0 . 2 (stat) ± 2 . 9 (syst) pb, and for the cross section ratio 0 . 017 ± 0 . 001 (stat) ± 0 . 001 (syst) and 0 . 020 ± 0 . 001 (stat) ± 0 . 001 (syst). The values of $$ {\\sigma}_{\\mathrm{t}\\overline{\\mathrm{t}}\\mathrm{b}\\overline{\\mathrm{b}}} $$ σ t t ¯ b b ¯ are determined from the product of the $$ {\\sigma}_{\\mathrm{t}\\overline{\\mathrm{t}}\\mathrm{jj}} $$ σ t t ¯ jj and the cross section ratio, obtaining, respectively, 0 . 040 ± 0 . 002 (stat) ± 0 . 005 (syst) pb and 0 . 62 ± 0 . 03 (stat) ± 0 . 07 (syst) pb. These measurements are the most precise to date and are consistent, within the uncertainties, with the standard model expectations obtained using a matrix element calculation at next-to-leading order in quantum chromodynamics matched to a parton shower.
Search for nonresonant Higgs boson pair production in final states with two bottom quarks and two photons in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 03-2021
Abstract: A search for nonresonant production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two photons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of $$ \\sqrt{s} $$ s = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb − 1 . No significant deviation from the background-only hypothesis is observed. An upper limit at 95% confidence level is set on the product of the Higgs boson pair production cross section and branching fraction into $$ \\gamma \\gamma \\mathrm{b}\\overline{\\mathrm{b}} $$ γγ b b ¯ . The observed (expected) upper limit is determined to be 0.67 (0 . 45) fb, which corresponds to 7.7 (5.2) times the standard model prediction. This search has the highest sensitivity to Higgs boson pair production to date. Assuming all other Higgs boson couplings are equal to their values in the standard model, the observed coupling modifiers of the trilinear Higgs boson self-coupling κ λ and the coupling between a pair of Higgs bosons and a pair of vector bosons c 2V are constrained within the ranges − 3 . 3 κ λ 8 . 5 and − 1 . 3 c 2V 3 . 5 at 95% confidence level. Constraints on κ λ are also set by combining this analysis with a search for single Higgs bosons decaying to two photons, produced in association with top quark-antiquark pairs, and by performing a simultaneous fit of κ λ and the top quark Yukawa coupling modifier κ t .
Search for dark photons in Higgs boson production via vector boson fusion in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 03-2021
Abstract: A search is presented for a Higgs boson that is produced via vector boson fusion and that decays to an undetected particle and an isolated photon. The search is performed by the CMS collaboration at the LHC, using a data set corresponding to an integrated luminosity of 130 fb − 1 , recorded at a center-of-mass energy of 13 TeV in 2016–2018. No significant excess of events above the expectation from the standard model background is found. The results are interpreted in the context of a theoretical model in which the undetected particle is a massless dark photon. An upper limit is set on the product of the cross section for production via vector boson fusion and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a Higgs boson mass of 125 GeV, assuming the standard model production rates, the observed (expected) 95% confidence level upper limit on the branching fraction is 3.5 (2.8)%. This is the first search for such decays in the vector boson fusion channel. Combination with a previous search for Higgs bosons produced in association with a Z boson results in an observed (expected) upper limit on the branching fraction of 2.9 (2.1)% at 95% confidence level.
Constraints on the Initial State of Pb-Pb Collisions via Measurements of
Z
Publisher: American Physical Society (APS)
Date: 31-08-2021
Search for new physics in top quark production with additional leptons in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV using effective field theory
Publisher: Springer Science and Business Media LLC
Date: 03-2021
Abstract: Events containing one or more top quarks produced with additional prompt leptons are used to search for new physics within the framework of an effective field theory (EFT). The data correspond to an integrated luminosity of 41.5 fb − 1 of proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, collected by the CMS experiment in 2017. The selected events are required to have either two leptons with the same charge or more than two leptons jets, including identified bottom quark jets, are also required, and the selected events are ided into categories based on the multiplicities of these objects. Sixteen dimension-six operators that can affect processes involving top quarks produced with additional charged leptons are considered in this analysis. Constructed to target EFT effects directly, the analysis applies a novel approach in which the observed yields are parameterized in terms of the Wilson coefficients (WCs) of the EFT operators. A simultaneous fit of the 16 WCs to the data is performed and two standard deviation confidence intervals for the WCs are extracted the standard model expectations for the WC values are within these intervals for all of the WCs probed.
Measurement of differential cross sections for Z bosons produced in association with charm jets in pp collisions at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 04-2021
Abstract: Measurements are presented of differential cross sections for the production of Z bosons in association with at least one jet initiated by a charm quark in pp collisions at $$ \sqrt{s} $$ s = 13 TeV. The data recorded by the CMS experiment at the LHC correspond to an integrated luminosity of 35.9 fb − 1 . The final states contain a pair of electrons or muons that are the decay products of a Z boson, and a jet consistent with being initiated by a charm quark produced in the hard interaction. Differential cross sections as a function of the transverse momentum p T of the Z boson and p T of the charm jet are compared with predictions from Monte Carlo event generators. The inclusive production cross section 405 . 4 ± 5 . 6 (stat) ± 24 . 3 (exp) ± 3 . 7 (theo) pb, is measured in a fiducial region requiring both leptons to have pseudorapidity |η| 2 . 4 and p T 10 GeV, at least one lepton with p T 26 GeV, and a mass of the pair in the range 71–111 GeV, while the charm jet is required to have p T 30 GeV and |η| 2 . 4. These are the first measurements of these cross sections in proton-proton collisions at 13 TeV.
Search for resonant and nonresonant new phenomena in high-mass dilepton final states at $$ \sqrt{s} $$ = 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 07-2021
Abstract: A search is presented for physics beyond the standard model (SM) using electron or muon pairs with high invariant mass. A data set of proton-proton collisions collected by the CMS experiment at the LHC at $$ \\sqrt{s} $$ s = 13 TeV from 2016 to 2018 corresponding to a total integrated luminosity of up to 140 fb − 1 is analyzed. No significant deviation is observed with respect to the SM background expectations. Upper limits are presented on the ratio of the product of the production cross section and the branching fraction to dileptons of a new narrow resonance to that of the Z boson. These provide the most stringent lower limits to date on the masses for various spin-1 particles, spin-2 gravitons in the Randall-Sundrum model, as well as spin-1 mediators between the SM and dark matter particles. Lower limits on the ultraviolet cutoff parameter are set both for four-fermion contact interactions and for the Arkani-Hamed, Dimopoulos, and Dvali model with large extra dimensions. Lepton flavor universality is tested at the TeV scale for the first time by comparing the dimuon and dielectron mass spectra. No significant deviation from the SM expectation of unity is observed.
Search for Resonances Decaying to Three
W
Publisher: American Physical Society (APS)
Date: 06-07-2022
Search for long-lived particles decaying to jets with displaced vertices in proton-proton collisions at
s<
Publisher: American Physical Society (APS)
Date: 28-09-2021
Evidence for Top Quark Production in Nucleus-Nucleus Collisions
Publisher: American Physical Society (APS)
Date: 24-11-2020
Observation of Bs 0
Publisher:
Elsevier BV
Date:
06-2022
Publisher: Elsevier BV
Date: 06-2022
Search for supersymmetry in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV in events with high-momentum Z bosons and missing transverse momentum
Publisher: Springer Science and Business Media LLC
Date: 09-2020
Abstract: A search for new physics in events with two highly Lorentz-boosted Z bosons and large missing transverse momentum is presented. The analyzed proton-proton collision data, corresponding to an integrated luminosity of 137 fb − 1 , were recorded at $$ \\sqrt{s} $$ s = 13 TeV by the CMS experiment at the CERN LHC. The search utilizes the substructure of jets with large radius to identify quark pairs from Z boson decays. Backgrounds from standard model processes are suppressed by requirements on the jet mass and the missing transverse momentum. No significant excess in the event yield is observed beyond the number of background events expected from the standard model. For a simplified supersymmetric model in which the Z bosons arise from the decay of gluinos, an exclusion limit of 1920 GeV on the gluino mass is set at 95% confidence level. This is the first search for beyond-standard-model production of pairs of boosted Z bosons plus large missing transverse momentum.
Measurement of the production cross section for
Z + b Publisher:
American Physical Society (APS)
Date:
31-05-2022
Publisher: American Physical Society (APS)
Date: 31-05-2022
Observation of the Production of Three Massive Gauge Bosons at
s =
Publisher:
American Physical Society (APS)
Date:
05-10-2020
Publisher: American Physical Society (APS)
Date: 05-10-2020
Search for long-lived heavy neutral leptons with displaced vertices in proton-proton collisions at $$ \sqrt{\mathrm{s}} $$ =13 TeV
Publisher: Springer Science and Business Media LLC
Date: 07-2019
Abstract: A search for heavy neutral leptons (HNLs), the right-handed Dirac or Majorana neutrinos, is performed in final states with three charged leptons (electrons or muons) using proton-proton collision data collected by the CMS experiment at $$ \\sqrt{s} $$ s = 13 TeV at the CERN LHC. The data correspond to an integrated luminosity of 138 fb − 1 . The HNLs could be produced through mixing with standard model neutrinos ν . For small values of the HNL mass ( 20 GeV) and the square of the HNL- ν mixing parameter (10 − 7 –10 − 2 ), the decay length of these particles can be large enough so that the secondary vertex of the HNL decay can be resolved with the CMS silicon tracker. The selected final state consists of one lepton emerging from the primary proton-proton collision vertex, and two leptons forming a displaced, secondary vertex. No significant deviations from the standard model expectations are observed, and constraints are obtained on the HNL mass and coupling strength parameters, excluding previously unexplored regions of parameter space in the mass range 1–20 GeV and squared mixing parameter values as low as 10 − 7 .
Search for resonant production of strongly coupled dark matter in proton-proton collisions at 13 TeV
Publisher: Springer Science and Business Media LLC
Date: 29-06-2022
Abstract: The first collider search for dark matter arising from a strongly coupled hidden sector is presented and uses a data s le corresponding to 138 fb −1 , collected with the CMS detector at the CERN LHC, at $$ \\sqrt{s} $$ s = 13 TeV. The hidden sector is hypothesized to couple to the standard model (SM) via a heavy leptophobic Z′ mediator produced as a resonance in proton-proton collisions. The mediator decay results in two “semivisible” jets, containing both visible matter and invisible dark matter. The final state therefore includes moderate missing energy aligned with one of the jets, a signature ignored by most dark matter searches. No structure in the dijet transverse mass spectra compatible with the signal is observed. Assuming the Z′ boson has a universal coupling of 0.25 to the SM quarks, an inclusive search, relevant to any model that exhibits this kinematic behavior, excludes mediator masses of 1.5–4.0 TeV at 95% confidence level, depending on the other signal model parameters. To enhance the sensitivity of the search for this particular class of hidden sector models, a boosted decision tree (BDT) is trained using jet substructure variables to distinguish between semivisible jets and SM jets from background processes. When the BDT is employed to identify each jet in the dijet system as semivisible, the mediator mass exclusion increases to 5.1 TeV, for wider ranges of the other signal model parameters. These limits exclude a wide range of strongly coupled hidden sector models for the first time.
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