Inclusive and differential cross section measurements of single top quark production in association with a Z boson in proton-proton collisions at √s = 13 TeV

Inclusive and differential cross sections of single top quark production in association with a Z boson are measured in proton-proton collisions at a center-of-mass energy of 13 TeV with a data sample corresponding to an integrated luminosity of 138 fb−1 recorded by the CMS experiment. Events are selected based on the presence of three leptons, electrons or muons, associated with leptonic Z boson and top quark decays. The measurement yields an inclusive cross section of 87.9 +7.5 −7.3 (stat)+7.3 −6.0 (syst) fb for a dilepton invariant mass greater than 30 GeV, in agreement with standard model (SM) calculations and represents the most precise determination to date. The ratio between the cross sections for the top quark and the top antiquark production in association with a Z boson is measured as 2.37+0.56 −0.42 (stat)+0.27 −0.13 (syst). Differential measurements at parton and particle levels are performed for the first time. Several kinematic observables are considered to study the modeling of the process. Results are compared to theoretical predictions with different assumptions on the source of the initial-state b quark and found to be in agreement, within the uncertainties. Additionally, the spin asymmetry, which is sensitive to the top quark polarization, is determined from the differential distribution of the polarization angle at parton level to be 0.54±0.16 (stat)±0.06 (syst), in agreement with SM prediction

Search for W′ bosons decaying to a top and a bottom quark at s=13TeV in the hadronic final state

A search is performed for W′ bosons decaying to a top and a bottom quark in the all-hadronic final state, in proton-proton collisions at a center-of-mass energy of 13TeV. The analyzed data were collected by the CMS experiment between 2016 and 2018 and correspond to an integrated luminosity of 137fb−1. Deep neural network algorithms are used to identify the jet initiated by the bottom quark and the jet containing the decay products of the top quark when the W boson from the top quark decays hadronically. No excess above the estimated standard model background is observed. Upper limits on the production cross sections of W′ bosons decaying to a top and a bottom quark are set. Both left- and right-handed W′ bosons with masses below 3.4TeV are excluded at 95% confidence level, and the most stringent limits to date on W′ bosons decaying to a top and a bottom quark in the all-hadronic final state are obtained.CMS Collaboration (ukupan broj autora: 2333

Measurement of the inclusive and differential t(t)over-bar gamma cross sections in the dilepton channel and effective field theory interpretation in proton-proton collisions at root s=13 TeV

WOS:000797503900001The production cross section of a top quark pair in association with a photon is measured in proton-proton collisions in the decay channel with two oppositely charged leptons (e(+/-)mu(-/+), e(+)e(-), or mu(+)mu(-)). The measurement is performed using 138 fb(-1) of proton-proton collision data recorded by the CMS experiment at root s = 13 TeV during the 2016-2018 data-taking period of the CERN LHC. A fiducial phase space is defined such that photons radiated by initial-state particles, top quarks, or any of their decay products are included. An inclusive cross section of 175.2 +/- 2.5(stat) +/- 6.3(syst) fb is measured in a signal region with at least one jet coming from the hadronization of a bottom quark and exactly one photon with transverse momentum above 20 GeV. Differential cross sections are measured as functions of several kinematic observables of the photon, leptons, and jets, and compared to standard model predictions. The measurements are also interpreted in the standard model effective field theory framework, and limits are found on the relevant Wilson coefficients from these results alone and in combination with a previous CMS measurement of the t (t) over bar gamma production process using the lepton+jets final state

Search for flavor-changing neutral current interactions of the top quark and the Higgs boson decaying to a bottom quark-antiquark pair at root s=13 TeV

WOS:000762281700001A search for flavor-changing neutral current interactions of the top quark (t) and the Higgs boson (H) is presented. The search is based on a data sample corresponding to an integrated luminosity of 137 fb(-1) recorded by the CMS experiment at the LHC in proton-proton collisions at root s = 13TeV. Events containing exactly one lepton (muon or electron) and at least three jets, among which at least two are identified as originating from the hadronization of a bottom quark, are analyzed. A set of deep neural networks is used for kinematic event reconstruction, while boosted decision trees distinguish the signal from the background events. No significant excess over the background predictions is observed, and upper limits on the signal production cross sections are extracted. These limits are interpreted in terms of top quark decay branching fractions (B) to the Higgs boson and an up (u) or a charm quark (c). Assuming one nonvanishing extra coupling at a time, the observed (expected) upper limits at 95% confidence level are B(t -> Hu) Hc) < 0.094 (0.086)%

Measurements of the electroweak diboson production cross sections in proton-proton collisions at s =5.02 TeV using leptonic decays

WOS:000719845900006PubMed ID34797136The first measurements of diboson production cross sections in proton-proton interactions at a center-of-mass energy of 5.02 TeV are reported. They are based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 302 pb-1. Events with two, three, or four charged light leptons (electrons or muons) in the final state are analyzed. The WW, WZ, and ZZ total cross sections are measured as σWW=37.0-5.2+5.5(stat)-2.6+2.7(syst) pb, σWZ=6.4-2.1+2.5(stat)-0.3+0.5(syst) pb, and σZZ=5.3-2.1+2.5(stat)-0.4+0.5(syst) pb. All measurements are in good agreement with theoretical calculations at combined next-to-next-to-leading order quantum chromodynamics and next-to-leading order electroweak accuracy

Search for long-lived particles decaying into muon pairs in proton-proton collisions at s√ = 13 TeV collected with a dedicated high-rate data stream

A search for long-lived particles decaying into muon pairs is performed using proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment at the LHC in 2017 and 2018, corresponding to an integrated luminosity of 101 fb−1. The data sets used in this search were collected with a dedicated dimuon trigger stream with low transverse momentum thresholds, recorded at high rate by retaining a reduced amount of information, in order to explore otherwise inaccessible phase space at low dimuon mass and nonzero displacement from the primary interaction vertex. No significant excess of events beyond the standard model expectation is found. Upper limits on branching fractions at 95% confidence level are set on a wide range of mass and lifetime hypotheses in beyond the standard model frameworks with the Higgs boson decaying into a pair of long-lived dark photons, or with a long-lived scalar resonance arising from a decay of a b hadron. The limits are the most stringent to date for substantial regions of the parameter space. These results can be also used to constrain models of displaced dimuons that are not explicitly considered in this paper. [Figure not available: see fulltext.]

Analysis of the CP structure of the Yukawa coupling between the Higgs boson and tau leptons in proton-proton collisions at root s=13 TeV

WOS:000807501200001The first measurement of the CP structure of the Yukawa coupling between the Higgs boson and tau leptons is presented. The measurement is based on data collected in proton-proton collisions at root s = 13 TeV by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb(-1). The analysis uses the angular correlation between the decay planes of tau leptons produced in Higgs boson decays. The effective mixing angle between CP-even and CP-odd tau Yukawa couplings is found to be -1 +/- 19 degrees, compared to an expected value of 0 +/- 21 degrees at the 68.3% confidence level. The data disfavour the pure CP-odd scenario at 3.0 standard deviations. The results are compatible with predictions for the standard model Higgs boson

Measurement of double-parton scattering in inclusive production of four jets with low transverse momentum in proton-proton collisions at root s=13 TeV

WOS:000748913900003A measurement of inclusive four-jet production in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. The transverse momenta of jets within vertical bar eta vertical bar 4.7 are required to exceed 35, 30, 25, and 20 GeV for the first-, second-, third-, and fourth-leading jet, respectively. Differential cross sections are measured as functions of the jet transverse momentum, jet pseudorapidity, and several other observables that describe the angular correlations between the jets. The measured distributions show sensitivity to different aspects of the underlying event, parton shower modeling, and matrix element calculations. In particular, the interplay between angular correlations caused by parton shower and double-parton scattering contributions is shown to be important. The double-parton scattering contribution is extracted by means of a template fit to the data, using distributions for single-parton scattering obtained from Monte Carlo event generators and a double-parton scattering distribution constructed from inclusive single-jet events in data. The effective double-parton scattering cross section is calculated and discussed in view of previous measurements and of its dependence on the models used to describe the single-parton scattering background

Measurement of the inclusive t t ¯ production cross section in proton-proton collisions at √s = 5.02 TeV

The top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data were collected in a special LHC low-energy and low-intensity run in 2017, and correspond to an integrated luminosity of 302 pb−1. The measurement is performed using events with one electron and one muon of opposite charge, and at least two jets. The measured cross section is 60.7 ± 5.0 (stat) ± 2.8 (syst) ± 1.1 (lumi) pb. A combination with the result in the single lepton + jets channel, based on data collected in 2015 at the same center-of-mass energy and corresponding to an integrated luminosity of 27.4 pb−1, is then performed. The resulting measured value is 63.0 ± 4.1 (stat) ± 3.0 (syst+lumi) pb, in agreement with the standard model prediction of 66.8−3.1+2.9 pb