15 research outputs found

    Search for high-mass resonances in final states with a lepton and missing transverse momentum at root s=13 TeV

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    A search for new high-mass resonances in proton-proton collisions having final states with an electron or muon and missing transverse momentum is presented. The analysis uses proton-proton collision data collected in 2016 with the CMS detector at the LHC at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 35.9 fb(-1). The transverse mass distribution of the charged lepton-neutrino system is used as the discriminating variable. No significant deviation from the standard model prediction is found. The best limit, from the combination of electron and muon channels, is 5.2TeV at 95% confidence level for the mass of a W' boson with the same couplings as those of the standard model Wboson. Exclusion limits of 2.9TeV are set on the inverse radius of the extra dimension in the framework of split universal extra dimensions. In addition, model-independent limits are set on the production cross section and coupling strength of W' bosons decaying into this final state. An interpretation is also made in the context of an R parity violating supersymmetric model with a slepton as a mediator and flavor violating decay.Peer reviewe

    Observation of the diphoton decay of the Higgs boson and measurement of its properties

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    Study of Vector Boson Scattering and Search for New Physics in Events with Two Same-Sign Leptons and Two Jets

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    A study of vector boson scattering in pp collisions at a center-of-mass energy of 8 TeV is presented. The data sample corresponds to an integrated luminosity of 19.4 fb(-1) collected with the CMS detector. Candidate events are selected with exactly two leptons of the same charge, two jets with large rapidity separation and high dijet mass, and moderate missing transverse energy. The signal region is expected to be dominated by electroweak same-sign W-boson pair production. The observation agrees with the standard model prediction. The observed significance is 2.0 standard deviations, where a significance of 3.1 standard deviations is expected based on the standard model. Cross section measurements for (WW +/-)-W-+/- and WZ processes in the fiducial region are reported. Bounds on the structure of quartic vector-boson interactions are given in the framework of dimension-eight effective field theory operators, as well as limits on the production of doubly charged Higgs bosons

    Search for a W or Techni-rho Decaying into WZ in pp Collisions at root s=7 TeV

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    A search is performed in pp collisions at root s 7 TeV for exotic particles decaying via WZ to final states with electrons and muons. The data sample corresponds to an integrated luminosity of approximately 5 fb(-1). No significant excess is observed in the data above the expected standard model background. Upper bounds at 95% confidence level are set on the production cross section of the W boson described by the sequential standard model and on the W WZ coupling. W bosons with masses below 1143 GeV are excluded. Limits are also set in the context of low-scale technicolor models, under a range of assumptions concerning the model parameters

    Search for a light charged Higgs boson decaying to c-sbar in pp collisions at sqrt(s) = 8 TeV

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    see paper for full list of authorsInternational audienceA search for a light charged Higgs boson, originating from the decay of a top quark and subsequently decaying into a charm quark and a strange antiquark, is presented. The data used in the analysis correspond to an integrated luminosity of 19.7 inverse-femtobarns recorded in proton-proton collisions at sqrt(s) = 8 TeV by the CMS experiment at the LHC. The search is performed in the process t tbar to W+/- b H-/+ bbar, where the W boson decays to a lepton (electron or muon) and a neutrino. The decays lead to a final state comprising an isolated lepton, at least four jets and large missing transverse energy. No significant deviation is observed in the data with respect to the standard model predictions, and model-independent upper limits are set on the branching fraction BF( t to H+ b ), ranging from 1.2 to 6.5% for a charged Higgs boson with mass between 90 and 160 GeV, under the assumption that BF( H+ to c sbar ) = 100%

    Measurement of transverse momentum relative to dijet systems in PbPb and pp collisions at sqrt(s) = 8 TeV

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    An analysis of dijet events in PbPb and pp collisions is performed to explore the properties of energy loss by partons traveling in a quark-gluon plasma. Data are collected at a nucleon-nucleon center-of-mass energy of 2.76 TeV at the LHC. The distribution of transverse momentum (pT) surrounding dijet systems is measured by selecting charged particles in different ranges of pT and at different angular cones of pseudorapidity and azimuth. The measurement is performed as a function of centrality of the PbPb collisions, the pT asymmetry of the jets in the dijet pair, and the distance parameter R used in the anti-kt jet clustering algorithm. In events with unbalanced dijets, PbPb collisions show an enhanced multiplicity in the hemisphere of the subleading jet, with the pT imbalance compensated by an excess of low-pT particles at large angles from the jet axes

    Observation of nuclear modifications in W± boson production in pPb collisions at sNN=8.16TeV

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    The production of W± bosons is studied in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of sNN=8.16TeV. Measurements are performed in the W±→μ±νμ channel using a data sample corresponding to an integrated luminosity of 173.4±6.1nb−1, collected by the CMS Collaboration at the LHC. The number of positively and negatively charged W bosons is determined separately in the muon pseudorapidity region in the laboratory frame |ηlabμ|25GeV/c. The W± boson differential cross sections, muon charge asymmetry, and the ratios of W± boson yields for the proton-going over the Pb-going beam directions are reported as a function of the muon pseudorapidity in the nucleon-nucleon centre-of-mass frame. The measurements are compared to the predictions from theoretical calculations based on parton distribution functions (PDFs) at next-to-leading-order. The results favour PDF calculations that include nuclear modifications and provide constraints on the nuclear PDF global fits

    A search for pair production of new light bosons decaying into muons in proton-proton collisions at 13 TeV

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    A search for new light bosons decaying into muon pairs is presented using a data sample corresponding to an integrated luminosity of 35.9fb−1 of proton-proton collisions at a center-of-mass energy s=13TeV, collected with the CMS detector at the CERN LHC. The search is model independent, only requiring the pair production of a new light boson and its subsequent decay to a pair of muons. No significant deviation from the predicted background is observed. A model independent limit is set on the product of the production cross section times branching fraction to dimuons squared times acceptance as a function of new light boson mass. This limit varies between 0.15 and 0.39fb over a range of new light boson masses from 0.25 to 8.5 GeV. It is then interpreted in the context of the next-to-minimal supersymmetric standard model and a dark supersymmetry model that allows for nonnegligible light boson lifetimes. In both cases, there is significant improvement over previously published limits

    Measurement of charged pion, kaon, and proton production in proton-proton collisions at root s=13 TeV

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    Transverse momentum spectra of charged pions, kaons, and protons are measured in proton-proton collisions at √s = 13 TeV with the CMS detector at the LHC. The particles, identified via their energy loss in the silicon tracker, are measured in the transverse momentum range of pT ∼ 0.1-1.7 GeV/c and rapidities /y/ < 1. The pT spectra and integrated yields are compared to previous results at smaller √s and to predictions of Monte Carlo event generators. The average pT increases with particle mass and charged particle multiplicity of the event. Comparisons with previous CMS results at √s = 0.9, 2.76, and 7 TeV show that the average pT and the ratios of hadron yields feature very similar dependences on the particle multiplicity in the event, independently of the center-of-mass energy of the pp collision
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