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0000-0002-3984-4732
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Deutsches Elektronen-Synchrotron
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Publisher: American Physical Society (APS)
Date: 05-10-2020
Publisher: Elsevier BV
Date: 09-2020
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.
Publisher: Elsevier BV
Date: 2021
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.
Publisher: Elsevier BV
Date: 08-2021
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.
Publisher: American Physical Society (APS)
Date: 10-09-2021
Publisher: American Physical Society (APS)
Date: 09-11-2020
Publisher: American Physical Society (APS)
Date: 16-11-2020
Publisher: IOP Publishing
Date: 15-09-2020
Publisher: American Physical Society (APS)
Date: 19-03-2021
Publisher: American Physical Society (APS)
Date: 24-04-2020
Publisher: American Physical Society (APS)
Date: 05-08-2020
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 09-2020
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.
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 05-2021
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 ¯ .
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.
Publisher: Elsevier BV
Date: 02-2021
Publisher: Springer Science and Business Media LLC
Date: 06-2020
Publisher: American Physical Society (APS)
Date: 12-08-2020
Publisher: American Physical Society (APS)
Date: 30-11-2020
Publisher: American Physical Society (APS)
Date: 20-08-2021
Publisher: American Physical Society (APS)
Date: 30-11-2020
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.
Publisher: American Physical Society (APS)
Date: 19-08-2020
Publisher: American Physical Society (APS)
Date: 07-12-2020
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.
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 08-2021
Publisher: Springer Science and Business Media LLC
Date: 06-2020
Publisher: American Physical Society (APS)
Date: 14-01-2021
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.
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.
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.
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.
Publisher: Elsevier BV
Date: 10-2020
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.
Publisher: American Physical Society (APS)
Date: 28-06-2022
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.
Publisher: Springer Science and Business Media LLC
Date: 04-2020
Publisher: Springer Science and Business Media LLC
Date: 05-2020
Publisher: Springer Science and Business Media LLC
Date: 05-2020
Publisher: IOP Publishing
Date: 20-08-2020
Publisher: American Physical Society (APS)
Date: 03-09-2020
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.
Publisher: IOP Publishing
Date: 05-05-2020
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.
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.
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 .
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.
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.
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.
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.
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.
Publisher: IOP Publishing
Date: 28-02-2020
Publisher: American Physical Society (APS)
Date: 22-06-2020
Publisher: American Physical Society (APS)
Date: 25-06-2021
Publisher: American Physical Society (APS)
Date: 25-06-2021
Publisher: American Physical Society (APS)
Date: 23-03-2022
Publisher: Elsevier BV
Date: 05-2021
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.
Publisher: Elsevier BV
Date: 12-2022
Publisher: Springer Science and Business Media LLC
Date: 06-2020
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.
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.
Publisher: American Physical Society (APS)
Date: 07-10-2020
Publisher: IOP Publishing
Date: 03-06-2020
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.
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.
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.
Publisher: American Physical Society (APS)
Date: 30-07-2021
Publisher: Springer Science and Business Media LLC
Date: 05-2020
Publisher: Springer Science and Business Media LLC
Date: 04-2020
Publisher: Elsevier BV
Date: 02-2020
Publisher: IOP Publishing
Date: 10-2020
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.
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.
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.
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.
Publisher: American Physical Society (APS)
Date: 26-08-2021
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 07-2020
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.
Publisher: IOP Publishing
Date: 19-10-2020
Publisher: Elsevier BV
Date: 03-2022
Publisher: IOP Publishing
Date: 08-02-2021
Publisher: American Physical Society (APS)
Date: 19-01-2022
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.
Publisher: Elsevier BV
Date: 2021
Publisher: American Physical Society (APS)
Date: 17-09-2021
Publisher: American Physical Society (APS)
Date: 21-05-2020
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.
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.
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.
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 .
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.
Publisher: American Physical Society (APS)
Date: 31-08-2021
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.
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.
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.
Publisher: American Physical Society (APS)
Date: 28-09-2021
Publisher: American Physical Society (APS)
Date: 24-11-2020
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.
Publisher: Elsevier BV
Date: 06-2022
Publisher: American Physical Society (APS)
Date: 05-10-2020
No related grants have been discovered for Volodymyr Myronenko.