Results 1 - 10 of 453
Results 1 - 10 of 453. Search took: 0.019 seconds
|Sort by: date | relevance|
[en] A search is presented for single production of a vector-like quark (T) decaying to a Z boson and a top quark, with the Z boson decaying leptonically and the top quark decaying hadronically. The search uses data collected by the CMS experiment in proton–proton collisions at a center-of-mass energy of 13 TeV in 2016, corresponding to an integrated luminosity of 35.9. The presence of forward jets is a particular characteristic of single production of vector-like quarks that is used in the analysis. For the first time, different T quark width hypotheses are studied, from negligibly small to 30% of the new particle mass. At the 95% confidence level, the product of cross section and branching fraction is excluded above values in the range 0.26–0.04 pb for T quark masses in the range 0.7–1.7 TeV, assuming a negligible width. A similar sensitivity is observed for widths of up to 30% of the T quark mass. The production of a heavy boson decaying to Tt, with , is also searched for, and limits on the product of cross section and branching fractions for this process are set between 0.13 and 0.06 pb for boson masses in the range from 1.5 to 2.5 TeV.
[en] A search is presented for narrow heavy resonances decaying to a top quark and a bottom quark using data collected by the CMS experiment at in 2016. The data set analyzed corresponds to an integrated luminosity of 35.9 . Final states that include a single lepton (e, μ), multiple jets, and missing transverse momentum are analyzed. No evidence is found for the production of a boson, and the production of right-handed bosons is excluded at 95% confidence level for masses up to 3.6 depending on the scenario considered. Exclusion limits for bosons are also presented as a function of their coupling strength to left- and right-handed fermions. These limits on a boson decaying via a top and a bottom quark are the most stringent published to date.
[en] An inclusive search for anomalous Higgs boson production in the diphoton decay channel and in association with at least one jet is presented, using LHC proton–proton collision data collected by the CMS experiment at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of . The razor variables and , as well as the momentum and mass resolution of the diphoton system, are used to categorize events into different search regions. The search result is interpreted in the context of strong and electroweak production of supersymmetric particles. We exclude bottom squark pair-production with masses below 450 GeV for bottom squarks decaying to a bottom quark, a Higgs boson, and the lightest supersymmetric particle (LSP) for LSP masses below 250 GeV. For wino-like chargino–neutralino production, we exclude charginos with mass below 170 GeV for LSP masses below 25 GeV. In the GMSB scenario, we exclude charginos with mass below 205 GeV for neutralinos decaying to a Higgs boson and a goldstino LSP with 100% branching fraction.
[en] A measurement is presented of the associated production of a single top quark and a Z boson. The study uses data from proton–proton collisions at recorded by the CMS experiment, corresponding to an integrated luminosity of 35.9 fb−1. Using final states with three leptons (electrons or muons), the tZq production cross section is measured to be , where ℓ stands for electrons, muons, or τ leptons, with observed and expected significances of 3.7 and 3.1 standard deviations, respectively.
[en] A search for the standard model (SM) Higgs boson (H) decaying to when produced in association with an electroweak vector boson is reported for the following processes: , , , , and . The search is performed in data samples corresponding to an integrated luminosity of 35.9 at recorded by the CMS experiment at the LHC during Run 2 in 2016. An excess of events is observed in data compared to the expectation in the absence of a signal. The significance of this excess is 3.3 standard deviations, where the expectation from SM Higgs boson production is 2.8. The signal strength corresponding to this excess, relative to that of the SM Higgs boson production, is . When combined with the Run 1 measurement of the same processes, the signal significance is 3.8 standard deviations with 3.8 expected. The corresponding signal strength, relative to that of the SM Higgs boson, is .
[en] Results are presented from a search for supersymmetry in events with a single electron or muon and hadronic jets. The data correspond to a sample of proton–proton collisions at with an integrated luminosity of 35.9, recorded in 2016 by the CMS experiment. A number of exclusive search regions are defined according to the number of jets, the number of b -tagged jets, the scalar sum of the transverse momenta of the jets, and the scalar sum of the missing transverse momentum and the transverse momentum of the lepton. Standard model background events are reduced significantly by requiring a large azimuthal angle between the direction of the lepton and of the reconstructed W boson, computed under the hypothesis that all of the missing transverse momentum in the event arises from a neutrino produced in the leptonic decay of the W boson. The numbers of observed events are consistent with the expectations from standard model processes, and the results are used to set lower limits on supersymmetric particle masses in the context of two simplified models of gluino pair production. In the first model, where each gluino decays to a top quark–antiquark pair and a neutralino, gluino masses up to 1.8 TeV are excluded at the 95% CL. The second model considers a three-body decay to a light quark–antiquark pair and a chargino, which subsequently decays to a W boson and a neutralino. In this model, gluinos are excluded up to 1.9 TeV.
[en] A search is presented for new physics in events with two low-momentum, oppositely charged leptons (electrons or muons) and missing transverse momentum in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data collected using the CMS detector at the LHC correspond to an integrated luminosity of 35.9. The observed event yields are consistent with the expectations from the standard model. The results are interpreted in terms of pair production of charginos and neutralinos ( and ) with nearly degenerate masses, as expected in natural supersymmetry models with light higgsinos, as well as in terms of the pair production of top squarks ( ), when the lightest neutralino and the top squark have similar masses. At 95% confidence level, wino-like masses are excluded up to 230 GeV for a mass difference of 20 GeV relative to the lightest neutralino. In the higgsino-like model, masses are excluded up to 168 GeV for the same mass difference. For pair production, top squark masses up to 450 GeV are excluded for a mass difference of 40 GeV relative to the lightest neutralino.
[en] A search for new physics in energetic, high-multiplicity final states has been performed using proton–proton collision data collected with the CMS detector at a center-of-mass energy of 13 and corresponding to an integrated luminosity of 2.3. The standard model background, dominated by multijet production, is determined exclusively from control regions in data. No statistically significant excess of events is observed. Model-independent limits on the product of the cross section and the acceptance of a new physics signal in these final states are set and further interpreted in terms of limits on the production of black holes. Semiclassical black holes and string balls with masses as high as 9.5, and quantum black holes with masses as high as 9.0 are excluded by this search in the context of models with extra dimensions, thus significantly extending limits set at a center-of-mass energy of 8 with the LHC Run 1 data.
[en] Measurements of azimuthal angle and transverse momentum ( ) correlations of isolated photons and associated jets are reported for and PbPb collisions at . The data were recorded with the CMS detector at the CERN LHC. For events containing a leading isolated photon with and an associated jet with , the photon+jet azimuthal correlation and imbalance in PbPb collisions are studied as functions of collision centrality and . The results are compared to reference data collected at the same collision energy and to predictions from several theoretical models for parton energy loss. No evidence of broadening of the photon+jet azimuthal correlations is observed, while the ratio decreases significantly for PbPb data relative to the reference. All models considered agree within uncertainties with the data. The number of associated jets per photon with is observed to be shifted towards lower values in central PbPb collisions compared to collisions.
[en] A search for long-lived particles was performed with data corresponding to an integrated luminosity of 2.6 fb−1 collected at a center-of-mass energy of 13 TeV by the CMS experiment in 2015. The analysis exploits two customized topological trigger algorithms, and uses the multiplicity of displaced jets to search for the presence of a signal decay occurring at distances between 1 and 1000 mm. The results can be interpreted in a variety of different models. For pair-produced long-lived particles decaying to two b quarks and two leptons with equal decay rates between lepton flavors, cross sections larger than 2.5 fb are excluded for proper decay lengths between 70–100 mm for a long-lived particle mass of 1130 GeV at 95% confidence. For a specific model of pair-produced, long-lived top squarks with R-parity violating decays to a b quark and a lepton, masses below 550–1130 GeV are excluded at 95% confidence for equal branching fractions between lepton flavors, depending on the squark decay length. This mass bound is the most stringent to date for top squark proper decay lengths greater than 3 mm.