A study of anomalous couplings of the Higgs boson to vector bosons and fermions is presented. The data were recorded by the CMS experiment at a center-of-mass energy of pp collisions at the LHC of ...13 TeV and correspond to an integrated luminosity of 138 fb-1 . The study uses Higgs boson candidates produced mainly in gluon fusion or electroweak vector boson fusion at the LHC that subsequently decay to a pair of τ leptons. Matrix-element and machine-learning techniques were employed in a search for anomalous interactions. The results are combined with those from the four-lepton and two-photon decay channels to yield the most stringent constraints on anomalous Higgs boson couplings to date. The pure CP -odd scenario of the Higgs boson coupling to gluons is excluded at 2.4 standard deviations. The results are consistent with the standard model predictions.
Multiparticle azimuthal correlations of prompt D0 mesons are measured in Pb-Pb collisions at a nucleon-nucleon center-of-mass energy of sNN=5.02 TeV . For the first time, a four-particle cumulant ...method is used to extract the second Fourier coefficient of the azimuthal distribution ( v2 ) of D0 mesons as a function of event centrality and the D0 transverse momentum. The ratios of the four-particle v2 values to previously measured two-particle cumulant results provide direct experimental access to event-by-event fluctuations of charm quark azimuthal anisotropies. These ratios are also found to be comparable to those of inclusive charged particles in the event. However, hints of deviations are seen in the most central and peripheral collisions. To investigate the origin of flow fluctuations in the charm sector, these measurements are compared to a model implementing fluctuations of charm quark energy loss via collisional or radiative processes in the quark-gluon plasma. These models cannot quantitatively describe the data over the full transverse momentum and centrality ranges, although the calculations with collisional energy loss provide a better description of the data.
Events where the two leading jets are separated by a pseudorapidity interval devoid of particle activity, known as jet-gap-jet events, are studied in proton-proton collisions at √s = 13 TeV. The ...signature is expected from hard color-singlet exchange. Each of the highest transverse momentum (pT) jets must have pjetT > 40 GeV and pseudorapidity 1.4 < |ηjet| < 4.7, with ηjet1 ηjet2 < 0, where jet1 and jet2 are the leading and subleading jets in pT, respectively. The analysis is based on data collected by the CMS and TOTEM experiments during a low luminosity, highβ run at the CERN LHC in 2015, with an integrated luminosity of 0.66 pb−1. Events with a low number of charged particles with pT > 0.2 GeV in the interval |η| < 1 between the jets are observed in excess of calculations that assume only color-exchange. The fraction of events produced via color-singlet exchange, fCSE, is measured as a function of pjet 2T, the pseudorapidity difference between the two leading jets, and the azimuthal angular separation between the two leading jets. The fraction fCSE has values of 0.4–1.0%. The results are compared with previous measurements and with predictions from perturbative quantum chromodynamics. In addition, the first study of jet-gap-jet events detected in association with an intact proton using a subsample of events with an integrated luminosity of 0.40 pb−1 is presented. The intact protons are detected with the Roman pot detectors of the TOTEM experiment. The fCSE in this sample is 2.91 ± 0.70(stat) +1.08−1.01 (syst) times larger than that for inclusive dijet production in dijets with similar kinematics.
Evidence is presented for the electroweak (EW) production of two jets (jj) in association with two Z bosons and constraints on anomalous quartic gauge couplings are set. The analysis is based on a ...data sample of proton-proton collisions at s=13TeV collected with the CMS detector in 2016–2018, and corresponding to an integrated luminosity of 137 fb-1 . The search is performed in the fully leptonic final state ZZ→ℓℓℓ'ℓ' , where ℓ,ℓ'=e,μ . The EW production of two jets in association with two Z bosons is measured with an observed (expected) significance of 4.0 (3.5) standard deviations. The cross sections for the EW production are measured in three fiducial volumes and the result is σEW(pp→ZZjj→ℓℓℓ'ℓ'jj)=0.33-0.10+0.11(stat)-0.03+0.04(syst)fb in the most inclusive volume, in agreement with the standard model prediction of 0.275±0.021fb . Measurements of total cross sections for jj production in association with two Z bosons are also reported. Limits on anomalous quartic gauge couplings are derived in terms of the effective field theory operators T0, T1, T2, T8, and T9.
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