174 research outputs found

    The CMS Statistical Analysis and Combination Tool: COMBINE

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    International audienceThis paper describes the COMBINE software package used for statistical analyses by the CMS Collaboration. The package, originally designed to perform searches for a Higgs boson and the combined analysis of those searches, has evolved to become the statistical analysis tool presently used in the majority of measurements and searches performed by the CMS Collaboration. It is not specific to the CMS experiment, and this paper is intended to serve as a reference for users outside of the CMS Collaboration, providing an outline of the most salient features and capabilities. Readers are provided with the possibility to run COMBINE and reproduce examples provided in this paper using a publicly available container image. Since the package is constantly evolving to meet the demands of ever-increasing data sets and analysis sophistication, this paper cannot cover all details of COMBINE. However, the online documentation referenced within this paper provides an up-to-date and complete user guide

    Dark sector searches with the CMS experiment

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    Astrophysical observations provide compelling evidence for gravitationally interacting dark matter in the universe that cannot be explained by the standard model of particle physics. The extraordinary amount of data from the CERN LHC presents a unique opportunity to shed light on the nature of dark matter at unprecedented collision energies. This Report comprehensively reviews the most recent searches with the CMS experiment for particles and interactions belonging to a dark sector and for dark-sector mediators. Models with invisible massive particles are probed by searches for signatures of missing transverse momentum recoiling against visible standard model particles. Searches for mediators are also conducted via fully visible final states. The results of these searches are compared with those obtained from direct-detection experiments. Searches for alternative scenarios predicting more complex dark sectors with multiple new particles and new forces are also presented. Many of these models include long-lived particles, which could manifest themselves with striking unconventional signatures with relatively small amounts of background. Searches for such particles are discussed and their impact on dark-sector scenarios is evaluated. Many results and interpretations have been newly obtained for this Report.Astrophysical observations provide compelling evidence for gravitationally interacting dark matter in the universe that cannot be explained by the standard model of particle physics. The extraordinary amount of data from the CERN LHC presents a unique opportunity to shed light on the nature of dark matter at unprecedented collision energies. This Report comprehensively reviews the most recent searches with the CMS experiment for particles and interactions belonging to a dark sector and for dark-sector mediators. Models with invisible massive particles are probed by searches for signatures of missing transverse momentum recoiling against visible standard model particles. Searches for mediators are also conducted via fully visible final states. The results of these searches are compared with those obtained from direct-detection experiments. Searches for alternative scenarios predicting more complex dark sectors with multiple new particles and new forces are also presented. Many of these models include long-lived particles, which could manifest themselves with striking unconventional signatures with relatively small amounts of background. Searches for such particles are discussed and their impact on dark-sector scenarios is evaluated. Many results and interpretations have been newly obtained for this Report

    Observation of double J/ψ\psi meson production in pPb collisions at sNN\sqrt{s_\mathrm{NN}} = 8.16 TeV

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    International audienceThe first observation of the concurrent production of two J/ψ\psi mesons in proton-nucleus collisions is presented. The analysis is based on a proton-lead (pPb) data sample recorded at a nucleon-nucleon center-of-mass energy of 8.16 TeV by the CMS experiment at the CERN LHC and corresponding to an integrated luminosity of 174.6 nb1^{-1}. The two J/ψ\psi mesons are reconstructed in their μ+μ\mu^+\mu^- decay channels with transverse momenta pTp_\mathrm{T}>\gt 6.5 GeV and rapidity y\lvert y \rvert<\lt 2.4. Events where one of the J/ψ\psi mesons is reconstructed in the dielectron channel are also considered in the search. The pPb \to J/ψ\psiJ/ψ\psi+X process is observed with a significance of 5.3 standard deviations. The measured inclusive fiducial cross section, using the four-muon channel alone, is σ\sigma(pPb\to J/ψ\psiJ/ψ\psi+X)= 22.0 ±\pm 8.9 (stat) ±\pm 1.5 (syst) nb. A fit of the data to the expected rapidity separation for pairs of J/ψ\psi mesons produced in single (SPS) and double (DPS) parton scatterings yields σSPSpPbJ/ψJ/ψ+X\sigma^{\mathrm{pPb}\to\mathrm{J}/\psi\mathrm{J}/\psi+\mathrm{X}}_\text{SPS} = 16.5 ±\pm 10.8 (stat) ±\pm 0.1 (syst) nb and σDPSpPbJ/ψJ/ψ+X\sigma^{\mathrm{pPb}\to \mathrm{J}/\psi\mathrm{J}/\psi+\mathrm{X}}_\text{DPS} = 5.4 ±\pm 6.2 (stat) ±\pm 0.4 (syst) nb, respectively. This latter result can be transformed into a lower bound on the effective DPS cross section, closely related to the squared average interparton transverse separation in the collision, of σeff\sigma_\text{eff}>\gt 1.0 mb at 95% confidence level

    Constraints on the Higgs boson self-coupling from the combination of single and double Higgs boson production in proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceThe Higgs boson (H) trilinear self-coupling, λ3\lambda_3, is constrained via its measured properties and limits on the HH pair production using the proton-proton collision data collected by the CMS experiment at s\sqrt{s} = 13 TeV. The combination of event categories enriched in single-H and HH events is used to measure κλ\kappa_\lambda, defined as the value of λ3\lambda_3 normalized to its standard model prediction, while simultaneously constraining the Higgs boson couplings to fermions and vector bosons. Values of κλ\kappa_\lambda outside the interval -1.2 <\ltκλ\kappa_\lambda<\lt 7.5 are excluded at 2σ\sigma confidence level, which is compatible with the expected range of -2.0 <\ltκλ\kappa_\lambda<\lt 7.7 under the assumption that all other Higgs boson couplings are equal to their standard model predicted values. Relaxing the assumption on the Higgs couplings to fermions and vector bosons the observed (expected) κλ\kappa_\lambda interval is constrained to be within -1.4 <\ltκλ\kappa_\lambda<\lt 7.8 (-2.3 <\ltκλ\kappa_\lambda<\lt 7.8) at 2σ\sigma confidence level

    Search for bottom quark associated production of the standard model Higgs boson in final states with leptons in proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceThis Letter presents the first search for bottom quark associated production of the standard model Higgs boson, in final states with leptons. Higgs boson decays to pairs of tau leptons and pairs of leptonically decaying W bosons are considered. The search is performed using data collected from 2016 to 2018 by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb1{-1}. Upper limits at the 95% confidence level are placed on the signal strength for Higgs boson production in association with bottom quarks; the observed (expected) upper limit is 3.7 (6.1) times the standard model prediction

    Dark sector searches with the CMS experiment

    No full text
    International audienceAstrophysical observations provide compelling evidence for gravitationally interacting dark matter in the universe that cannot be explained by the standard model of particle physics. The extraordinary amount of data from the CERN LHC presents a unique opportunity to shed light on the nature of dark matter at unprecedented collision energies. This Report comprehensively reviews the most recent searches with the CMS experiment for particles and interactions belonging to a dark sector and for dark-sector mediators. Models with invisible massive particles are probed by searches for signatures of missing transverse momentum recoiling against visible standard model particles. Searches for mediators are also conducted via fully visible final states. The results of these searches are compared with those obtained from direct-detection experiments. Searches for alternative scenarios predicting more complex dark sectors with multiple new particles and new forces are also presented. Many of these models include long-lived particles, which could manifest themselves with striking unconventional signatures with relatively small amounts of background. Searches for such particles are discussed and their impact on dark-sector scenarios is evaluated. Many results and interpretations have been newly obtained for this Report

    Search for light long-lived particles decaying to displaced jets in proton-proton collisions at s\sqrt{s} = 13.6 TeV

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    International audienceA search for light long-lived particles decaying to displaced jets is presented, using a data sample of proton-proton collisions at a center-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 34.7 fb1^{-1}, collected with the CMS detector at the CERN LHC in 2022. Novel trigger, reconstruction, and machine-learning techniques were developed for and employed in this search. After all selections, the observations are consistent with the background predictions. Limits are presented on the branching fraction of the Higgs boson to long-lived particles that subsequently decay to quark pairs or tau lepton pairs. An improvement by up to a factor of 10 is achieved over previous limits for models with long-lived particle masses smaller than 60 GeV and proper decay lengths smaller than 1 m. The first constraints are placed on the fraternal twin Higgs and folded supersymmetry models, where the lower bounds on the top quark partner mass reach up to 350 GeV for the fraternal twin Higgs model and 250 GeV for the folded supersymmetry model

    Measurement of the Bs0^0_\mathrm{s}\to J/ψ\psiKS0^0_\mathrm{S} effective lifetime from proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceThe effective lifetime of the Bs0^0_\mathrm{s} meson in the decay Bs0^0_\mathrm{s}\to J/ψ\psiKS0^0_\mathrm{S} is measured using data collected during 2016-2018 with the CMS detector in s\sqrt{s} = 13 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 140 fb1^{-1}. The effective lifetime is determined by performing a two-dimensional unbinned maximum likelihood fit to the Bs0^0_\mathrm{s} meson invariant mass and proper decay time distributions. The resulting value of 1.59 ±\pm 0.07 (stat) ±\pm 0.03 (syst) ps is the most precise measurement to date and is in good agreement with the expected value

    Measurement of inclusive and differential cross sections of single top quark production in association with a W boson in proton-proton collisions at s\sqrt{s} = 13.6 TeV

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    International audienceThe first measurement of the inclusive and normalised differential cross sections of single top quark production in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13.6 TeV is presented. The data were recorded with the CMS detector at the LHC in 2022, and correspond to an integrated luminosity of 34.7 fb1^{-1}. The analysed events contain one muon and one electron in the final state. For the inclusive measurement, multivariate discriminants exploiting the kinematic properties of the events are used to separate the signal from the dominant top quark-antiquark production background. A cross section of 82.3 ±\pm 2.1 (stat) 9.7+9.9{}^{+9.9}_{-9.7} (syst) ±\pm 3.3 (lumi) pb is obtained, consistent with the predictions of the standard model. A fiducial region is defined according to the detector acceptance to perform the differential measurements. The resulting differential distributions are unfolded to particle level and show good agreement with the predictions at next-to-leading order in perturbative quantum chromodynamics

    Study of WH production through vector boson scattering and extraction of the relative sign of the W and Z couplings to the Higgs boson in proton-proton collisions at s\sqrt{s} = 13 TeV

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    A search for the production of a W boson and a Higgs boson through vector boson scattering (VBS) is presented, using CMS data from proton-proton collisions at s\sqrt{s} = 13 TeV collected from 2016 to 2018. The integrated luminosity of the data sample is 138 fb1^{-1}. Selected events must be consistent with the presence of two jets originating from VBS, the leptonic decay of the W boson to an electron or muon, and a Higgs boson decaying into a pair of b quarks, reconstructed as either a single merged jet or two resolved jets. A measurement of the process as predicted by the standard model (SM) is performed alongside a study of beyond-the-SM (BSM) scenarios. The SM analysis sets an observed (expected) 95% confidence level upper limit of 14.3 (9.0) on the ratio of the measured VBS WH cross section to that expected by the SM. The BSM analysis, conducted within the so-called κ\kappa framework, excludes all scenarios with λWZ\lambda_\mathrm{WZ} <\lt 0 that are consistent with current measurements, where λWZ\lambda_\mathrm{WZ} = κW/κZ\kappa_\mathrm{W}/\kappa_\mathrm{Z} and κW\kappa_\mathrm{W} and κZ\kappa_\mathrm{Z} are the HWW and HZZ coupling modifiers, respectively. The signficance of the exclusion is beyond 5 standard deviations, and it is consistent with the SM expectation of λWZ\lambda_\mathrm{WZ} = 1
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