120 research outputs found

    Measurement of the mass difference between top quark and antiquark in pp collisions at root s=8 TeV

    Get PDF
    Peer reviewe

    Measurement of the inclusive 3-jet production differential cross section in proton-proton collisions at 7 TeV and determination of the strong coupling constant in the TeV range

    Get PDF
    This paper presents a measurement of the inclusive 3-jet production differential cross section at a proton–proton centre-of-mass energy of 7 TeV using data corresponding to an integrated luminosity of 5 fb-1 collected with the CMS detector. The analysis is based on the three jets with the highest transverse momenta. The cross section is measured as a function of the invariant mass of the three jets in a range of 445–3270 GeV and in two bins of the maximum rapidity of the jets up to a value of 2. A comparison between the measurement and the prediction from perturbative QCD at next-to-leading order is performed. Within uncertainties, data and theory are in agreement. The sensitivity of the observable to the strong coupling constant αS is studied. A fit to all data points with 3-jet masses larger than 664 GeV gives a value of the strong coupling constant of αS(MZ)=0.1171±0.0013(exp)-0.0047+0.0073(theo)

    Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs

    Get PDF
    Constraints are presented on the total width of the recently discovered Higgs boson, &#915;H , using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1 fb&#8722;1 at a center-of-mass energy s=7 TeV and 19.7 fb&#8722;1 at s=8 TeV . A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of &#915;H<22 MeV at a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of mH=125.6 GeV

    Search for heavy neutrinos and W bosons with right-handed couplings in proton - proton collisions at \sqrt = 8TeV

    Get PDF
    A search for heavy, right-handed neutrinos, N&#8467; ( &#8467;=e,&#956; ), and right-handed WR bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS experiment. The search was based on a sample of two lepton plus two jet events collected in proton&#8211;proton collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb-1 . For models with strict left-right symmetry, and assuming only one N&#8467; flavor contributes significantly to the WR decay width, the region in the two-dimensional (MWR,MN&#8467;) mass plane excluded at a 95 % confidence level extends to approximately MWR=3.0TeV and covers a large range of neutrino masses below the WR boson mass, depending on the value of MWR . This search significantly extends the (MWR,MN&#8467;) exclusion region beyond previous results. Electronic supplementary material The online version of this article (doi:10.1140/epjc/s10052-014-3149-z) contains supplementary material, which is available to authorized users

    Search for jet extinction in the inclusive jet-pT spectrum from proton-proton collisions at s=8 TeV

    Get PDF
    Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.The first search at the LHC for the extinction of QCD jet production is presented, using data collected with the CMS detector corresponding to an integrated luminosity of 10.7  fb−1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The extinction model studied in this analysis is motivated by the search for signatures of strong gravity at the TeV scale (terascale gravity) and assumes the existence of string couplings in the strong-coupling limit. In this limit, the string model predicts the suppression of all high-transverse-momentum standard model processes, including jet production, beyond a certain energy scale. To test this prediction, the measured transverse-momentum spectrum is compared to the theoretical prediction of the standard model. No significant deficit of events is found at high transverse momentum. A 95% confidence level lower limit of 3.3 TeV is set on the extinction mass scale

    Measurement of the production cross section for a W boson and two b jets in pp collisions at root s=7 TeV

    Get PDF
    The production cross section for a W boson and two b jets is measured using proton&#8211;proton collisions at s=7 TeV in a data sample collected with the CMS experiment at the LHC corresponding to an integrated luminosity of 5.0 fb &#8722;1 . The W+bb¯ events are selected in the W&#8594;&#956;&#957; decay mode by requiring a muon with transverse momentum pT>25 GeV and pseudorapidity |&#951;|25 GeV and |&#951;|<2.4 . The measured W+bb¯ production cross section in the fiducial region, calculated at the level of final-state particles, is &#963;(pp&#8594;W+bb¯)×B(W&#8594;&#956;&#957;)=0.53±0.05(stat.)±0.09(syst.)±0.06(theo.)±0.01(lum.) pb , in agreement with the standard model prediction. In addition, kinematic distributions of the W+bb¯ system are in agreement with the predictions of a simulation using MadGraph and pythia

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

    Get PDF
    The tt¯ charge asymmetry in proton-proton collisions at s&#8730; = 7 TeV is measured using the dilepton decay channel (ee, e &#956; , or &#956;&#956; ). The data correspond to a total integrated luminosity of 5.0 fb &#8722;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 = &#8722;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

    Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at=2.76 TeV

    Get PDF

    Measurement of the t-channel single-top-quark production cross section and of the |Vtb| CKM matrix element in pp collisions at SQR = 8 TeV

    Get PDF
    Measurements are presented of the t -channel single-top-quark production cross section in proton-proton collisions at s&#8730; = 8 TeV. The results are based on a data sample corresponding to an integrated luminosity of 19.7 fb &#8722;1 recorded with the CMS detector at the LHC. The cross section is measured inclusively, as well as separately for top (t) and antitop (t¯) , in final states with a muon or an electron. The measured inclusive t -channel cross section is &#963; t -ch. = 83 . 6 ± 2 . 3 (stat.) ± 7 . 4 (syst.) pb. The single t and t¯ cross sections are measured to be &#963; t -ch. ( t ) = 53 . 8 ± 1 . 5 (stat.) ± 4 . 4 (syst.) pb and &#963; t -ch. (t¯) = 27 . 6 ± 1 . 3 (stat.) ± 3 . 7 (syst.) pb, respectively. The measured ratio of cross sections is R t -ch. = &#963; t -ch. (t) /&#963; t -ch. (t¯) = 1 . 95 ± 0 . 10 (stat.) ± 0 . 19 (syst.), in agreement with the standard model prediction. The modulus of the Cabibbo-Kobayashi-Maskawa matrix element V tb is extracted and, in combination with a previous CMS result at s&#8730; = 7 TeV, a value | V tb | = 0 . 998 ± 0 . 038 (exp.) ± 0 . 016 (theo.) is obtained

    Observation of a peaking structure in the J/psi phi mass spectrum from B(+/-) to J/psi phi K(+/-) decays

    Get PDF
    corecore