101 research outputs found

    Mechanical stability of the CMS strip tracker measured with a laser alignment system

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    Search for direct production of supersymmetric partners of the top quark in the all-jets final state in proton-proton collisions at root s=13 TeV

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    Search for direct production of supersymmetric partners of the top quark in the all-jets final state in proton-proton collisions at √s = 13 TeV

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    A search for direct production of top squark pairs in events with jets and large transverse momentum imbalance is presented. The data are based on proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector in 2016 at the CERN LHC, and correspond to an integrated luminosity of 35.9 fb−1. The search considers a variety of R-parity conserving supersymmetric models, including ones for which the top squark and neutralino masses are nearly degenerate. Specialized jet reconstruction tools are developed to exploit the unique characteristics of the signal topologies. With no significant excess of events observed above the standard model expectations, upper limits are set on the direct top squark pair production cross section in the context of simplified supersymmetric models for various decay hypotheses. Models with larger differences in mass between the top squark and neutralino are probed for masses up to 1040 and 500 GeV, respectively, whereas models with a more compressed mass hierarchy are probed up to 660 and 610 GeV, respectively. The smallest mass difference probed is for masses near to 550 and 540 GeV, respectively

    Search for massive resonances decaying into WW, WZ or ZZ bosons in proton-proton collisions at √s=13TeV

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    Measurements of the pp -> W gamma gamma and pp -> Z gamma gamma cross sections and limits on anomalous quartic gauge couplings at root s=8 TeV

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    Principal-component analysis of two-particle azimuthal correlations in PbPb and pPb collisions at CMS

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    Measurements of t(t)over-bar cross sections in association with b jets and inclusive jets and their ratio using dilepton final states in pp collisions at root s=13 TeV

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    The cross sections for the production of t (t) over bar b (b) over bar and t (t) over bar jj events and their ratio sigma(t (t) over bar b (b) over bar)/sigma(t (t) over bar jj) are measured using data corresponding to an integrated luminosity of 2.3 fb(-1) collected in pp collisions at root s = 13 TeV with the CMS detector at the LHC. Events with two leptons (e or mu) and at least four reconstructed jets, including at least two identified as b quark jets, in the final state are selected. In the full phase space, the measured ratio is 0.022 +/- 0.003 (stat) +/- 0.006 (syst), the cross section sigma(t (t) over bar b (b) over bar) bis 4.0 +/- 0.6 (stat)+/- 1.3 (syst) pb and sigma(t (t) over bar jj) is 184 +/- 6 (stat)+/- 33 (syst) pb. The measurements are compared with the standard model expectations obtained from a POWHEG simulation at next-to-leading-order interfaced with PYTHIA. (c) 2017 The Author. Published by Elsevier B.V.Peer reviewe

    Coherent J/psi photoproduction in ultra-peripheral PbPb collisions at root s(NN)=2.76 TeV with the CMS experiment

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