A measurement is presented of differential cross sections for t-channel single top quark and antiquark production in proton-proton collisions at a centre-of-mass energy of 13 Formula omitted by the ...CMS experiment at the LHC. From a data set corresponding to an integrated luminosity of 35.9 Formula omitted, events containing one muon or electron and two or three jets are analysed. The cross section is measured as a function of the top quark transverse momentum ( Formula omitted), rapidity, and polarisation angle, the charged lepton Formula omitted and rapidity, and the Formula omitted of the Formula omitted boson from the top quark decay. In addition, the charge ratio is measured differentially as a function of the top quark, charged lepton, and Formula omitted boson kinematic observables. The results are found to be in agreement with standard model predictions using various next-to-leading-order event generators and sets of parton distribution functions. Additionally, the spin asymmetry, sensitive to the top quark polarisation, is determined from the differential distribution of the polarisation angle at parton level to be Formula omitted, in agreement with the standard model prediction.
A search is presented for a heavy vector resonance decaying into a Formula omitted boson and the standard model Higgs boson, where the Formula omitted boson is identified through its leptonic decays ...to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137 Formula omitted. Upper limits are derived on the production of a narrow heavy resonance Formula omitted, and a mass below 3.5 and 3.7 Formula omitted is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet Formula omitted model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3 Formula omitted for a Formula omitted mass between 0.8 and 4.6 Formula omitted, respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.
Normalised multi-differential cross sections for top quark pair ( Formula omitted) production are measured in proton-proton collisions at a centre-of-mass energy of 13 Formula omitted using events ...containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of Formula omitted. The double-differential Formula omitted cross section is measured as a function of the kinematic properties of the top quark and of the Formula omitted system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the Formula omitted system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength Formula omitted and the top quark pole mass ( Formula omitted) using several sets of parton distribution functions (PDFs). The measurement of Formula omitted exploits the sensitivity of the Formula omitted invariant mass distribution to Formula omitted near the production threshold. Furthermore, a simultaneous fit of the PDFs, Formula omitted, and Formula omitted is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of Formula omitted and Formula omitted. The values Formula omitted and Formula omitted are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the Formula omitted production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of Formula omitted of the order of Formula omitted, which can be regarded as additional theoretical uncertainty in the current Formula omitted extraction.
A search is presented for lepton-flavor violating decays of the Higgs boson to μτ and eτ . The dataset corresponds to an integrated luminosity of 137 fb-1 collected at the LHC in proton-proton ...collisions at a center-of-mass energy of 13 TeV. No significant excess has been found, and the results are interpreted in terms of upper limits on lepton-flavor violating branching fractions of the Higgs boson. The observed (expected) upper limits on the branching fractions are, respectively, B ( H → μτ ) <0.15 ( 0.15 ) % and B ( H → eτ ) <0.22 ( 0.16 ) % at 95% confidence level.
A search is presented for Formula omitted slepton pairs produced in proton-proton collisions at a center-of-mass energy of 13 Formula omitted. The search is carried out in events containing two ...Formula omitted leptons in the final state, on the assumption that each Formula omitted slepton decays primarily to a Formula omitted lepton and a neutralino. Events are considered in which each Formula omitted lepton decays to one or more hadrons and a neutrino, or in which one of the Formula omitted leptons decays instead to an electron or a muon and two neutrinos. The data, collected with the CMS detector in 2016 and 2017, correspond to an integrated luminosity of 77.2 Formula omitted. The observed data are consistent with the standard model background expectation. The results are used to set 95% confidence level upper limits on the cross section for Formula omitted slepton pair production in various models for Formula omitted slepton masses between 90 and 200 Formula omitted and neutralino masses of 1, 10, and 20 Formula omitted. In the case of purely left-handed Formula omitted slepton production and decay to a Formula omitted lepton and a neutralino with a mass of 1 Formula omitted, the strongest limit is obtained for a Formula omitted slepton mass of 125 Formula omitted at a factor of 1.14 larger than the theoretical cross section.
The standard model (SM) production of four top quarks ( Formula omitted) in proton-proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016-2018 data taking ...of the LHC, corresponds to an integrated luminosity of 137 Formula omitted at a center-of-mass energy of 13 Formula omitted. The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the Formula omitted signal are respectively 2.6 and 2.7 standard deviations, and the Formula omitted cross section is measured to be Formula omitted. The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, Formula omitted, yielding a limit of Formula omitted at Formula omitted confidence level, where Formula omitted is the SM value of Formula omitted. They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework, Formula omitted. Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350-470 Formula omitted and 350-550 Formula omitted for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.
A search for Formula omitted production from double-parton scattering processes using same-charge electron-muon and dimuon events is reported, based on proton-proton collision data collected at a ...center-of-mass energy of Formula omitted. The analyzed data set corresponds to an integrated luminosity of Formula omitted, collected using the CMS detector at the LHC in 2016 and 2017. Multivariate classifiers are used to discriminate between the signal and the dominant background processes. A maximum likelihood fit is performed to extract the signal cross section. This leads to the first evidence for Formula omitted production via double-parton scattering, with a significance of 3.9 standard deviations. The measured inclusive cross section is Formula omitted.
Two related searches for phenomena beyond the standard model (BSM) are performed using events with hadronic jets and significant transverse momentum imbalance. The results are based on a sample of ...proton-proton collisions at a center-of-mass energy of Formula omitted, collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 137 Formula omitted. The first search is inclusive, based on signal regions defined by the hadronic energy in the event, the jet multiplicity, the number of jets identified as originating from bottom quarks, and the value of the kinematic variable Formula omitted for events with at least two jets. For events with exactly one jet, the transverse momentum of the jet is used instead. The second search looks in addition for disappearing tracks produced by BSM long-lived charged particles that decay within the volume of the tracking detector. No excess event yield is observed above the predicted standard model background. This is used to constrain a range of BSM models that predict the following: the pair production of gluinos and squarks in the context of supersymmetry models conserving R-parity, with or without intermediate long-lived charginos produced in the decay chain; the resonant production of a colored scalar state decaying to a massive Dirac fermion and a quark; or the pair production of scalar and vector leptoquarks each decaying to a neutrino and a top, bottom, or light-flavor quark. In most of the cases, the results obtained are the most stringent constraints to date.
The rate for Higgs ( Formula omitted) bosons production in association with either one ( Formula omitted) or two ( Formula omitted) top quarks is measured in final states containing multiple ...electrons, muons, or tau leptons decaying to hadrons and a neutrino, using proton-proton collisions recorded at a center-of-mass energy of Formula omitted by the CMS experiment. The analyzed data correspond to an integrated luminosity of 137 Formula omitted. The analysis is aimed at events that contain Formula omitted, Formula omitted, or Formula omitted decays and each of the top quark(s) decays either to lepton+jets or all-jet channels. Sensitivity to signal is maximized by including ten signatures in the analysis, depending on the lepton multiplicity. The separation among Formula omitted, Formula omitted, and the backgrounds is enhanced through machine-learning techniques and matrix-element methods. The measured production rates for the Formula omitted and Formula omitted signals correspond to Formula omitted and Formula omitted of their respective standard model (SM) expectations. The corresponding observed (expected) significance amounts to 4.7 (5.2) standard deviations for Formula omitted, and to 1.4 (0.3) for Formula omitted production. Assuming that the Higgs boson coupling to the tau lepton is equal in strength to its expectation in the SM, the coupling Formula omitted of the Higgs boson to the top quark divided by its SM expectation, Formula omitted, is constrained to be within Formula omitted or Formula omitted, at 95% confidence level. This result is the most sensitive measurement of the Formula omitted production rate to date.
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