Non-Gaussian elliptic-flow fluctuations in PbPb collisions at √sNN = 5.02 TeV

This work is licensed under a Creative Commons Attribution 4.0 International License.Event-by-event fluctuations in the elliptic-flow coefficient v2 are studied in PbPb collisions at √sNN = 5.02 TeV using the CMS detector at the CERN LHC. Elliptic-flow probability distributions p(v2) for charged particles with transverse momentum 0.3 < pT < 3.0 GeV/c and pseudorapidity |η| < 1.0 are determined for different collision centrality classes. The moments of the p(v2) distributions are used to calculate the v2 coefficients based on cumulant orders 2, 4, 6, and 8. A rank ordering of the higher-order cumulant results and nonzero standardized skewness values obtained for the p(v2) distributions indicate nonGaussian initial-state fluctuations. Bessel–Gaussian and elliptic power fits to the flow distributions are studied to characterize the initial-state spatial anisotropy

Measurement of electroweak WZ boson production and search for new physics in WZ + two jets events in pp collisions at √s = 13 TeV

This work is licensed under a Creative Commons Attribution 4.0 International License.A measurement of WZ electroweak (EW) vector boson scattering is presented. The measurement is performed in the leptonic decay modes WZ → ν , where , = e,μ. The analysis is based on a data sample of proton-proton collisions at √s = 13 TeV at the LHC collected with the CMS detector and corresponding to an integrated luminosity of 35.9 fb−1. The WZ plus two jet production cross section is measured in fiducial regions with enhanced contributions from EW production and found to be consistent with standard model predictions. The EW WZ production in association with two jets is measured with an observed (expected) significance of 2.2 (2.5) standard deviations. Constraints on charged Higgs boson production and on anomalous quartic gauge couplings in terms of dimension-eight effective field theory operators are also presented

Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at √sNN = 5.02 TeV

This work is licensed under a Creative Commons Attribution 4.0 International License.Evidence for the light-by-light scattering process, γγ → γγ , in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 μb−1 recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy Eγ T > 2 GeV, pseudorapidity |ηγ | 5 GeV, diphoton transverse momentum pγγ T < 1 GeV, and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0 ± 0.9 (Theo) events for the signal and 4.0 ± 1.2 (stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light-by-light scattering signal. The measured fiducial light-by-light scattering cross section, σfid(γγ → γγ ) = 120±46 (stat)±28 (syst)±12 (theo) nb, is consistent with the standard model prediction. The mγγ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the γγ → a → γγ process, in the mass range ma = 5–90 GeV

Observation of prompt J/ψ meson elliptic flow in high-multiplicity pPb collisions at √sNN = 8.16 TeV

This work is licensed under a Creative Commons Attribution 4.0 International License.A measurement of the elliptic flow (v2) of prompt J/ψ mesons in high-multiplicity pPb collisions is reported using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy √sNN = 8.16 TeV. Prompt J/ψ mesons decaying into two muons are reconstructed in the rapidity region in the nucleon-nucleon center-of-mass frame (ycm), corresponding to either −2.86 < ycm < −1.86 or 0.94 < ycm < 1.94. The average v2 result from the two rapidity ranges is reported over the transverse momentum (pT) range from 0.2 to 10 GeV. Positive v2 values are observed for the prompt J/ψ meson, as extracted from long-range two-particle correlations with charged hadrons, for 2 < pT < 8 GeV. The prompt J/ψ results are compared with previous CMS measurements of elliptic flow for open charm mesons (D0) and strange hadrons. From these measurements, constraints can be obtained on the collective dynamics of charm quarks produced in high multiplicity events arising from small systems

Combination of CMS searches for heavy resonances decaying to pairs of bosons or leptons

This work is licensed under a Creative Commons Attribution 4.0 International License.A statistical combination of searches for heavy resonances decaying to pairs of bosons or leptons is presented. The data correspond to an integrated luminosity of 35.9 fb−1 collected during 2016 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data are found to be consistent with expectations from the standard model background. Exclusion limits are set in the context of models of spin-1 heavy vector triplets and of spin-2 bulk gravitons. For massdegenerate W and Z resonances that predominantly couple to the standard model gauge bosons, the mass exclusion at 95% confidence level of heavy vector bosons is extended to 4.5 TeV as compared to 3.8 TeV determined from the best individual channel. This excluded mass increases to 5.0 TeV if the resonances couple predominantly to fermions

Search for long-lived particles using nonprompt jets and missing transverse momentum with proton-proton collisions at √s = 13 TeV

This work is licensed under a Creative Commons Attribution 4.0 International License.A search for long-lived particles decaying to displaced, nonprompt jets and missing transverse momentum is presented. The data sample corresponds to an integrated luminosity of 137 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC in 2016–2018. Candidate signal events containing nonprompt jets are identified using the timing capabilities of the CMS electromagnetic calorimeter. The results of the search are consistent with the background prediction and are interpreted using a gauge-mediated supersymmetry breaking reference model with a gluino next-to-lightest supersymmetric particle. In this model, gluino masses up to 2100, 2500, and 1900 GeV are excluded at 95% confidence level for proper decay lengths of 0.3, 1, and 100 m, respectively. These are the best limits to date for such massive gluinos with proper decay lengths greater than ∼0.5m

Measurements of properties of the Higgs boson decaying to a W boson pair in pp collisions at √s = 13 TeV

This work is licensed under a Creative Commons Attribution 4.0 International License.Measurements of the production of the standard model Higgs boson decaying to a W boson pair are reported. The W+W− candidates are selected in events with an oppositely charged lepton pair, large missing transverse momentum, and various numbers of jets. To select Higgs bosons produced via vector boson fusion and associated production with a W or Z boson, events with two jets or three or four leptons are also selected. The event sample corresponds to an integrated luminosity of 35.9 fb−1, collected in pp collisions at √s = 13 TeV by the CMS detector at the LHC during 2016. Combining all channels, the observed cross section times branching fraction is 1.28+0.18−0.17 times the standard model prediction for the Higgs boson with a mass of 125.09 GeV. This is the first observation of the Higgs boson decay to W boson pairs by the CMS experiment

Measurement of associated production of a W boson and a charm quark in proton–proton collisions at √=13TeV

This work is licensed under a Creative Commons Attribution 4.0 International License.Measurements are presented of associated production of a W boson and a charm quark (W+c) in proton–proton collisions at a center-of-mass energy of 13TeV. The data correspond to an integrated luminosity of 35.7fb−1 collected by the CMS experiment at the CERN LHC. The W bosons are identified by their decay into a muon and a neutrino. The charm quarks are tagged via the full reconstruction of D∗(2010)± mesons that decay via D∗(2010)±→D0+±→K∓+±+±. A cross section is measured in the fiducial region defined by the muon transverse momentum T>26GeV, muon pseudorapidity ||5GeV. The inclusive cross section for this kinematic range is (W+c)=1026±31(stat)+76−72(syst) pb. The cross section is also measured differentially as a function of the pseudorapidity of the muon from the W boson decay. These measurements are compared with theoretical predictions and are used to probe the strange quark content of the proton

A search for pair production of new light bosons decaying into muons in proton-proton collisions at 13 TeV

This work is licensed under a Creative Commons Attribution 4.0 International License.A search for new light bosons decaying into muon pairs is presented using a data sample corresponding to an integrated luminosity of 35.9 fb−1 of proton-proton collisions at a center-of mass energy √s = 13 TeV, collected with the CMS detector at the CERN LHC. The search is model independent, only requiring the pair production of a new light boson and its subsequent decay to a pair of muons. No significant deviation from the predicted background is observed. A model independent limit is set on the product of the production cross section times branching fraction to dimuons squared times acceptance as a function of new light boson mass. This limit varies between 0.15 and 0.39 fb over a range of new light boson masses from 0.25 to 8.5 GeV. It is then interpreted in the context of the next-to-minimal supersymmetric standard model and a dark supersymmetry model that allows for nonnegligible light boson lifetimes. In both cases, there is significant improvement over previously published limits