ORCID Profile
0000-0001-7379-4540
Current Organisation
Universität Hamburg
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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.
Publisher: Springer Science and Business Media LLC
Date: 09-08-2023
Abstract: Measurements of the inclusive and differential fiducial cross sections for the Higgs boson production in the H → ZZ → 4 ℓ ( ℓ = e , μ ) decay channel are presented. The results are obtained from the analysis of proton-proton collision data recorded by the CMS experiment at the CERN LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb − 1 . The measured inclusive fiducial cross section is 2 . 73 ± 0 . 26 fb, in agreement with the standard model expectation of 2 . 86 ± 0 . 1 fb. Differential cross sections are measured as a function of several kinematic observables sensitive to the Higgs boson production and decay to four leptons. A set of double-differential measurements is also performed, yielding a comprehensive characterization of the four leptons final state. Constraints on the Higgs boson trilinear coupling and on the bottom and charm quark coupling modifiers are derived from its transverse momentum distribution. All results are consistent with theoretical predictions from the standard model.
Publisher: Springer Science and Business Media LLC
Date: 06-10-2023
Publisher: American Physical Society (APS)
Date: 10-10-2023
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 .
Publisher: American Physical Society (APS)
Date: 20-05-2022
Publisher: American Physical Society (APS)
Date: 09-2023
Publisher: Springer Science and Business Media LLC
Date: 06-10-2023
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.
No related grants have been discovered for Christopher Matthies.