A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at √s = 13 TeV, corresponding to an integrated luminosity of 137 fb−1, recorded with ...the CMS detector. The coupling strength with respect to the standard model value, Yt, is determined from kinematic distributions in tt final states containing ee, μμ, or eμ pairs. Variations of the Yukawa coupling strength lead to modified distributions for tt production. In particular, the distributions of the mass of the tt system and the rapidity difference of the top quark and antiquark are sensitive to the value of Yt. The measurement yields a best fit value of ..., bounding Y t < 1.54 at a 95% confidence level. (ProQuest: ... denotes formula omitted.).
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.
A fiducial cross section for Wγ production in proton-proton collisions is measured at a center-of-mass energy of 13 TeV in 137 fb−1 of data collected using the CMS detector at the LHC. The W → e ν ...and μ ν decay modes are used in a maximum-likelihood fit to the lepton-photon invariant mass distribution to extract the combined cross section. The measured cross section is compared with theoretical expectations at next-to-leading order in quantum chromodynamics. In addition, 95% confidence level intervals are reported for anomalous triple-gauge couplings within the framework of effective field theory.
The production of four top quarks (tt¯tt¯) is studied with LHC proton-proton collision data samples collected by the CMS experiment at a center-of-mass energy of 13 TeV, and corresponding to ...integrated luminosities of up to 138fb−1. Events that have no leptons (all-hadronic), one lepton, or two opposite-sign leptons (where lepton refers only to prompt electrons or prompt muons) are considered. This is the first tt¯tt¯ measurement that includes the all-hadronic final state. The observed significance of the tt¯tt¯ signal in these final states of 3.9 standard deviations (1.5 expected) provides evidence for tt¯tt¯ production, with a measured cross section of 36−11+12fb. Combined with earlier CMS results in other final states, the signal significance is 4.0 standard deviations (3.2 expected). The combination returns an observed cross section of 17±4(stat)±3(syst)fb, which is consistent with the standard model prediction.
The 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+5.5−5.2(stat)+2.7−2.6(syst)pb, σWZ = 6. 4+2.5−2.1(stat)+0.5−0.3(syst) pb, and σZZ = 5.3+2.5−2.1(stat)+0.5−0.4(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.
The leptonic and inclusive hadronic decay branching fractions of the W boson are measured using proton-proton collision data collected at s=13 TeV by the CMS experiment at the CERN LHC, corresponding ...to an integrated luminosity of 35.9 fb-1 . Events characterized by the production of one or two W bosons are selected and categorized based on the multiplicity and flavor of reconstructed leptons, the number of jets, and the number of jets identified as originating from the hadronization of b quarks. A binned maximum likelihood estimate of the W boson branching fractions is performed simultaneously in each event category. The measured branching fractions of the W boson decaying into electron, muon, and tau lepton final states are ( 10.83±0.10 ) % , ( 10.94±0.08 ) % , and ( 10.77±0.21 ) % , respectively, consistent with lepton flavor universality for the weak interaction. The average leptonic and inclusive hadronic decay branching fractions are estimated to be ( 10.89±0.08 ) % and ( 67.32±0.23 ) % , respectively. Based on the hadronic branching fraction, three standard model quantities are subsequently derived: the sum of squared elements in the first two rows of the Cabibbo–Kobayashi–Maskawa (CKM) matrix Σij | Vij | 2=1.984±0.021 , the CKM element | Vcs | =0.967±0.011 , and the strong coupling constant at the W boson mass scale, α S ( mW2 ) =0.095±0.033 .
A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, $H → c\bar{c}$, produced in association with a leptonically decaying $V (W \text{or} Z)$ boson is presented. The ...search is performed with proton-proton collisions at $\sqrt{s}=13\,\text {TeV}$ collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb-1. Novel charm jet identification and analysis methods using machine learning techniques are employed. The analysis is validated by searching for $Z → c\bar{c}$ in $VZ$ events, leading to its first observation at a hadron collider with a significance of 5.7 standard deviations. The observed (expected) upper limit on $σ(VH)\mathscr{B}(H → c\bar{c}$) is 0.94 (0.50$^{+0.22}_{– 0.15}$)pb at 95% confidence level (C.L.), corresponding to 14 (7.6$^{+3.4}_{–2.3}$) times the standard model prediction. For the Higgs-charm Yukawa coupling modifier, $κ_c$, the observed (expected) 95% C.L. interval is 1.1 < |$κ_c$| < 5.5 (|$κ_c$| < 3.4), the most stringent constraint to date.
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