270 research outputs found

    Measurements of differential production cross sections for a Z boson in association with jets in pp collisions at root s=8 TeV

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    Search for leptophobic Z ' bosons decaying into four-lepton final states in proton-proton collisions at root s=8 TeV

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    Search for black holes and other new phenomena in high-multiplicity final states in proton-proton collisions at root s=13 TeV

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    Search for heavy resonances decaying into a vector boson and a Higgs boson in final states with charged leptons, neutrinos, and b quarks

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    Search for high-mass diphoton resonances in proton-proton collisions at 13 TeV and combination with 8 TeV search

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    Search for the associated production of the Higgs boson with a top-quark pair

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    A search for the standard model Higgs boson produced in association with a top-quark pair t t ¯ H (tt¯H) is presented, using data samples corresponding to integrated luminosities of up to 5.1 fb −1 and 19.7 fb −1 collected in pp collisions at center-of-mass energies of 7 TeV and 8 TeV respectively. The search is based on the following signatures of the Higgs boson decay: H → hadrons, H → photons, and H → leptons. The results are characterized by an observed t t ¯ H tt¯H signal strength relative to the standard model cross section, μ = σ/σ SM ,under the assumption that the Higgs boson decays as expected in the standard model. The best fit value is μ = 2.8 ± 1.0 for a Higgs boson mass of 125.6 GeV

    Measurement of the Z boson differential cross section in transverse momentum and rapidity in proton-proton collisions at 8 TeV

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    We present a measurement of the Z boson differential cross section in rapidity and transverse momentum using a data sample of pp collision events at a centre-of-mass energy s=8 TeV, corresponding to an integrated luminosity of 19.7 fb-1. The Z boson is identified via its decay to a pair of muons. The measurement provides a precision test of quantum chromodynamics over a large region of phase space. In addition, due to the small experimental uncertainties in the measurement the data has the potential to constrain the gluon parton distribution function in the kinematic regime important for Higgs boson production via gluon fusion. The results agree with the next-to-next-to-leading-order predictions computed with the fewz program. The results are also compared to the commonly used leading-order MadGraph and next-to-leading-order powheg generators. © 2015 CERN for the benefit of the CMS Collaboration

    Measurement of prompt Jψ\psi pair production in pp collisions at \sqrt s = 7 Tev

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    Production of prompt J/ ψ meson pairs in proton-proton collisions at s s√ = 7 TeV is measured with the CMS experiment at the LHC in a data sample corresponding to an integrated luminosity of about 4.7 fb −1 . The two J/ ψ mesons are fully reconstructed via their decays into μ + μ − pairs. This observation provides for the first time access to the high-transverse-momentum region of J/ ψ pair production where model predictions are not yet established. The total and differential cross sections are measured in a phase space defined by the individual J/ ψ transverse momentum ( p T J/ ψ ) and rapidity (| y J/ ψ |): | y J/ ψ | 6.5 GeV/ c ; 1.2 4.5 GeV/ c . The total cross section, assuming unpolarized prompt J/ ψ pair production is 1.49 ± 0.07 (stat) ±0.13 (syst) nb. Different assumptions about the J/ ψ polarization imply modifications to the cross section ranging from −31% to +27%

    Measurements of the t(t)Overbar charge asymmetry using the dilepton decay channel in pp collisions at root s=7 TeV

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    The tt¯ charge asymmetry in proton-proton collisions at s√ = 7 TeV is measured using the dilepton decay channel (ee, e μ , or μμ ). The data correspond to a total integrated luminosity of 5.0 fb −1 , collected by the CMS experiment at the LHC. The tt and lepton charge asymmetries, defined as the differences in absolute values of the rapidities between the reconstructed top quarks and antiquarks and of the pseudorapidities between the positive and negative leptons, respectively, are measured to be A C = −0 . 010 ± 0 . 017 (stat . ) ± 0 . 008 (syst . ) and AlepC = 0 . 009 ± 0 . 010 (stat . ) ± 0 . 006 (syst . ). The lepton charge asymmetry is also measured as a function of the invariant mass, rapidity, and transverse momentum of the tt¯ system. All measurements are consistent with the expectations of the standard model

    Phenomenological MSSM interpretation of CMS searches in pp collisions at √s=7 and 8 TeV

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    Searches for new physics by the CMS collaboration are interpreted in the framework of the phenomenological minimal supersymmetric standard model (pMSSM). The data samples used in this study were collected at root s = 7 and 8 TeV and have integrated luminosities of 5.0 fb(-1) and 19.5 fb(-1), respectively. A global Bayesian analysis is performed, incorporating results from a broad range of CMS supersymmetry searches, as well as constraints from other experiments. Because the pMSSM incorporates several well-motivated assumptions that reduce the 120 parameters of the MSSM to just 19 parameters defined at the electroweak scale, it is possible to assess the results of the study in a relatively straightforward way. Approximately half of the model points in a potentially accessible subspace of the pMSSM are excluded, including all pMSSM model points with a gluino mass below 500 GeV, as well as models with a squark mass less than 300 GeV. Models with chargino and neutralino masses below 200 GeV are disfavored, but no mass range of model points can be ruled out based on the analyses considered. The nonexcluded regions in the pMSSM parameter space are characterized in terms of physical processes and key observables, and implications for future searches are discussed
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