The CMS Statistical Analysis and Combination Tool: COMBINE

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

Search for long-lived heavy neutrinos in the decays of B mesons produced in proton-proton collisions at s\sqrt{s} = 13 TeV

International audienceA search for long-lived heavy neutrinos (N) in the decays of \PB mesons produced in proton-proton collisions at $\sqrt{s}$ = 13 TeV is presented. The data sample corresponds to an integrated luminosity of 41.6 fb$^{-1}$ collected in 2018 by the CMS experiment at the CERN LHC, using a dedicated data stream that enhances the number of recorded events containing B mesons. The search probes heavy neutrinos with masses in the range 1 $\lt$$m_\mathrm{N}$$\lt$ 3 GeV and decay lengths in the range 10$^{-2}$$\lt$$c\tau$$\lt$ 10$^{4}$ mm, where $\tau_\mathrm{N}$ is the N proper mean lifetime. Signal events are defined by the signature B $\to$$\ell_\mathrm{B}$NX; N $\to$$\ell^{\pm} \pi^{\mp}$, where the leptons $\ell_\mathrm{B}$ and $\ell$ can be either a muon or an electron, provided that at least one of them is a muon. The hadronic recoil system, X, is treated inclusively and is not reconstructed. No significant excess of events over the standard model background is observed in any of the $\ell^{\pm}\pi^{\mp}$ invariant mass distributions. Limits at 95% confidence level on the sum of the squares of the mixing amplitudes between heavy and light neutrinos, $\vert V_\mathrm{N}\vert^2$, and on $c\tau$ are obtained in different mixing scenarios for both Majorana and Dirac-like N particles. The most stringent upper limit $\vert V_\mathrm{N}\vert^2$ $\lt$ 2.0$\times$10$^{-5}$ is obtained at $m_\mathrm{N}$ = 1.95 GeV for the Majorana case where N mixes exclusively with muon neutrinos. The limits on $\vert V_\mathrm{N}\vert^2$ for masses 1 $\lt$ $m_\mathrm{N}$ $\lt$ 1.7 GeV are the most stringent from a collider experiment to date

Dark sector searches with the CMS experiment

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

International audienceThe first observation of the concurrent production of two J/$\psi$ 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 nb$^{-1}$. The two J/$\psi$ mesons are reconstructed in their $\mu^+\mu^-$ decay channels with transverse momenta $p_\mathrm{T}$$\gt$ 6.5 GeV and rapidity $\lvert y \rvert$$\lt$ 2.4. Events where one of the J/$\psi$ mesons is reconstructed in the dielectron channel are also considered in the search. The pPb $\to$ J/$\psi$J/$\psi$+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 $\sigma$(pPb$\to$ J/$\psi$J/$\psi$+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/$\psi$ mesons produced in single (SPS) and double (DPS) parton scatterings yields $\sigma^{\mathrm{pPb}\to\mathrm{J}/\psi\mathrm{J}/\psi+\mathrm{X}}_\text{SPS}$ = 16.5 $\pm$ 10.8 (stat) $\pm$ 0.1 (syst) nb and $\sigma^{\mathrm{pPb}\to \mathrm{J}/\psi\mathrm{J}/\psi+\mathrm{X}}_\text{DPS}$ = 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 $\sigma_\text{eff}$$\gt$ 1.0 mb at 95% 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

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 fb${-1}$. 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

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

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 fb$^{-1}$, 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

International audienceThe effective lifetime of the B$^0_\mathrm{s}$ meson in the decay B$^0_\mathrm{s}$$\to$ J/$\psi$K$^0_\mathrm{S}$ is measured using data collected during 2016-2018 with the CMS detector in $\sqrt{s}$ = 13 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 140 fb$^{-1}$. The effective lifetime is determined by performing a two-dimensional unbinned maximum likelihood fit to the B$^0_\mathrm{s}$ 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

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

International audienceThe Higgs boson (H) trilinear self-coupling, $\lambda_3$, 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 $\sqrt{s}$ = 13 TeV. The combination of event categories enriched in single-H and HH events is used to measure $\kappa_\lambda$, defined as the value of $\lambda_3$ normalized to its standard model prediction, while simultaneously constraining the Higgs boson couplings to fermions and vector bosons. Values of $\kappa_\lambda$ outside the interval $-$1.2 $\lt$$\kappa_\lambda$$\lt$ 7.5 are excluded at 2$\sigma$ confidence level, which is compatible with the expected range of $-$2.0 $\lt$$\kappa_\lambda$$\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) $\kappa_\lambda$ interval is constrained to be within $-$1.4 $\lt$$\kappa_\lambda$$\lt$ 7.8 ($-$2.3 $\lt$$\kappa_\lambda$$\lt$ 7.8) at 2$\sigma$ confidence level