81 Search Results

A measurement of the top quark pair ($$ \textrm{t}\overline{\textrm{t}} $$) production cross section in proton-proton collisions at a centre-of-mass energy of 5.02 TeV is presented. The data were collected at the LHC in autumn 2017, in dedicated runs with low-energy and low-intensity conditions with respect to the default configuration, and correspond to an integrated luminosity of 302 pb$$^{−1}$$. The measurement is performed using events with one electron or muon, and multiple jets, at least one of them being identified as originating from a b quark (b tagged). Events are classified based on the number of all reconstructed jets and ofmore » b-tagged jets. Multivariate analysis techniques are used to enhance the separation between the signal and backgrounds. The measured cross section is $$ 62.5\pm 1.6{\left(\textrm{stat}\right)}_{-2.5}^{+2.6}\left(\textrm{syst}\right)\pm 1.2\left(\textrm{lumi}\right) $$ pb. A combination with the result in the dilepton channel based on the same data set yields a value of 62.3 ± 1.5 (stat) ± 2.4 (syst) ± 1.2 (lumi) pb, to be compared with the standard model prediction of $$ {69.5}_{-3.7}^{+3.5} $$ pb at next-to-next-to-leading order in perturbative quantum chromodynamics.« less

A search is presented for rare decays of the Z and Higgs bosons to a photon and a J∕ψ or a ψ(2S) meson, with the charmonium state subsequentially decaying to a pair of muons. The data set corresponds to an integrated luminosity of 123 fb⁻¹ of proton-proton collisions at a center-of-mass energy of 13TeV collected with the CMS detector at the LHC. No evidence for branching fractions of these rare decay channels larger than predicted in the standard model is observed. Upper limits at 95% confidence level are set: $$\mathcal{B}$$(H → J∕ψγ ) < 2.6 × 10⁻⁴, $$\mathcal{B}$$(H → ψ(2S)γmore » ) < 9.9 × 10⁻⁴, $$\mathcal{B}$$(Z → J∕ψγ ) < 0.6 × 10⁻⁶, and $$\mathcal{B}$$(Z → ψ(2S)γ ) < 1.3 × 10⁻⁶. The ratio of the Higgs boson coupling modifiers 𝜅_c∕𝜅_γ is constrained to be in the interval (−157, +199) at 95% confidence level. Assuming 𝜅_γ = 1, this interval becomes (−166, +208).« less

Measurements are presented of inclusive and differential cross sections for Z boson associated production of top quark pairs ($$ \textrm{t}\overline{\textrm{t}}\textrm{Z} $$) and single top quarks (tZq or tWZ). The data were recorded in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$$^{−1}$$. Events with three or more leptons, electrons or muons, are selected and a multiclass deep neural network is used to separate three event categories, the $$ \textrm{t}\overline{\textrm{t}}\textrm{Z} $$ and tWZ processes, the tZq process, and the backgrounds. A profile likelihood approach is used to unfold the differential cross sections, tomore » account for systematic uncertainties, and to determine the correlations between the two signal categories in one global fit. The inclusive cross sections for a dilepton invariant mass between 70 and 110 GeV are measured to be 1.14 ± 0.07 pb for the sum of $$ \textrm{t}\overline{\textrm{t}}\textrm{Z} $$ and tWZ, and 0.81 ± 0.10 pb for tZq, in good agreement with theoretical predictions.[graphic not available: see fulltext]« less

A search is presented for a heavy resonance decaying into a Z boson and a Higgs (H) boson. The analysis is based on data from proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb$$^{−1}$$, recorded with the CMS experiment in the years 2016–2018. Resonance masses between 1.4 and 5 TeV are considered, resulting in large transverse momenta of the Z and H bosons. Final states that result from Z boson decays to pairs of electrons, muons, or neutrinos are considered. The H boson is reconstructed as a single large-radius jet, recoiling againstmore » the Z boson. Machine-learning flavour-tagging techniques are employed to identify decays of a Lorentz-boosted H boson into pairs of charm or bottom quarks, or into four quarks via the intermediate H → WW$$^{*}$$ and ZZ$$^{*}$$ decays. The analysis targets H boson decays that were not generally included in previous searches using the H → $$ \textrm{b}\overline{\textrm{b}} $$ channel. Compared with previous analyses, the sensitivity for high resonance masses is improved significantly in the channel where at most one b quark is tagged.[graphic not available: see fulltext]« less

Three rare decay processes of the Higgs boson to a ρ(770)⁰, Φ(1020), or K^⁎(892)⁰ meson and a photon are searched for using $$\sqrt{s} = 13$$ TeV proton-proton collision data collected by the CMS experiment at the LHC. Events are selected assuming the mesons decay into a pair of charged pions, a pair of charged kaons, or a charged kaon and pion, respectively. Depending on the Higgs boson production mode, different triggering and reconstruction techniques are adopted. The analyzed data sets correspond to integrated luminosities up to 138 fb^-1, depending on the reconstructed final state. After combining various data sets andmore » categories, no significant excess above the background expectations is observed. Upper limits at 95% confidence level on the Higgs boson branching fractions into ρ(770)⁰$$γ$$, Φ(1020)$$γ$$, and K^⁎(892)⁰ are determined to be 3.7 x 10^-4, 3.0 x 10^-4, and 3.0 x 10^-4, respectively. In case of the ρ(770)⁰$$γ$$ and Φ(1020)$$γ$$ channels, these are the most stringent experimental limits to date.« less

A search is reported for charge-parity $CP$ violation in D$^0$$$$\to$$ K$$^0_\mathrm{S}$$K$$^0_\mathrm{S}$$ decays, using data collected in proton-proton collisions at $$\sqrt{s}$$ = 13 TeV recorded by the CMS experiment in 2018. The analysis uses a dedicated data set that corresponds to an integrated luminosity of 41.6 fb$$^{-1}$$, which consists of about 10 billion events containing a pair of b hadrons, nearly all of which decay to charm hadrons. The flavor of the neutral D meson is determined by the pion charge in the reconstructed decays D$$^{*+}$$$$\to$$ D$$^0\pi^+$$ and D$$^{*-}$$$$\to$$ D$$^0\pi^-$$. The $CP$ asymmetry in D$^0$$$$\to$$ K$$^0_\mathrm{S}$$K$$^0_\mathrm{S}$$ is measured to be $$A_{CP}$$(K$$^0_\mathrm{S}$$K$$^0_\mathrm{S}$$)more » = (6.2 $$\pm$$ 3.0 $$\pm$$ 0.2 $$\pm$$ 0.8)%, where the three uncertainties represent the statistical uncertainty, the systematic uncertainty, and the uncertainty in the measurement of the $CP$ asymmetry in the D$^0$ $$\to$$ K$$^0_\mathrm{S}\pi^+\pi^-$$ decay. This is the first $CP$ asymmetry measurement by CMS in the charm sector as well as the first to utilize a fully hadronic final state.« less

A measurement is performed of Higgs bosons produced with high transverse momentum (p$$_{T}$$) via vector boson or gluon fusion in proton-proton collisions. The result is based on a data set with a center-of-mass energy of 13 TeV collected in 2016–2018 with the CMS detector at the LHC and corresponds to an integrated luminosity of 138 fb$$^{−1}$$. The decay of a high-p$$_{T}$$ Higgs boson to a boosted bottom quark-antiquark pair is selected using large-radius jets and employing jet substructure and heavy-flavor taggers based on machine learning techniques. Independent regions targeting the vector boson and gluon fusion mechanisms are defined based onmore » the topology of two quark-initiated jets with large pseudorapidity separation. The signal strengths for both processes are extracted simultaneously by performing a maximum likelihood fit to data in the large-radius jet mass distribution. The observed signal strengths relative to the standard model expectation are $$ {4.9}_{-1.6}^{+1.9} $$ and $$ {1.6}_{-1.5}^{+1.7} $$ for the vector boson and gluon fusion mechanisms, respectively. A differential cross section measurement is also reported in the simplified template cross section framework.[graphic not available: see fulltext]« less

Searches for pair-produced multijet signatures using data corresponding to an integrated luminosity of $128{\mathrm{fb}}^{-1}$ of proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ are presented. A data scouting technique is employed to record events with low jet scalar transverse momentum sum values. The electroweak production of particles predicted in $R$ -parity violating supersymmetric models is probed for the first time with fully hadronic final states. This is the first search for prompt hadronically decaying mass-degenerate higgsinos, andmore » extends current exclusions on $R$ -parity violating top squarks and gluinos.« less

This 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 andmore » 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.« less

The effective lifetime of the $$ {\textrm{B}}_{\textrm{s}}^0 $$ meson in the decay $$ {\textrm{B}}_{\textrm{s}}^0\to \textrm{J}/{\uppsi \textrm{K}}_{\textrm{S}}^0 $$ 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 $$ {\textrm{B}}_{\textrm{s}}^0 $$ meson invariant mass and proper decay time distributions. The resulting value of 1.59 ± 0.07(stat) ± 0.03(syst) ps is the most precise measurement to date and is in good agreement with the expected value.[graphicmore » not available: see fulltext]« less