8 research outputs found

    Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at root s(NN)=5.02 TeV

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    Evidence for the light-by-light scattering process, gamma gamma -> gamma gamma, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 mu b(-1) recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy E-T(gamma) > 2 GeV, pseudorapidity vertical bar eta(gamma)vertical bar 5 GeV, diphoton transverse momentum p(T)(gamma gamma) gamma gamma) = 120 +/- 46(stat) +/- 28(syst) +/- 12(theo) nb, is consistent with the standard model prediction. The m(gamma gamma) distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the gamma gamma -> a -> gamma gamma process, in the mass range m(a) = 5-90 GeV. (C) 2019 The Author(s). Published by Elsevier B.V.Peer reviewe

    Search for Higgs and Z boson decays to J/psi or Y pairs in the four-muon final state in proton-proton collisions at root s=13 TeV<bold> </bold>

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    A search for decays of the Higgs and Z boson to pairs of J/psi or Y(nS)(n = 1, 2, 3) mesons, with their subsequent decay to mu(+)mu(-) pairs, is presented. The analysis uses data from proton-proton collisions at root s = 13 TeV, collected with the CMS detector at the LHC in 2017 and corresponding to an integrated luminosity of 37.5 fb(-1). While an observation of such a decay with this sample would indicate the presence of physics beyond the standard model, no significant excess is observed. Upper limits at 95% confidence level are placed on the branching fractions of these decays. In the J/psi pair channel, the limits are 1.8 x 10(-3) and 2.2 x 10(-6) for the Higgs and Z boson, respectively, while in the combined Y(nS) pair channel, the limits are 1.4 x 10(-3) and 1.5 x 10(-6), respectively, when the mesons from the Higgs and Z boson decay are assumed to be unpolarized. When fully longitudinal and transverse polarizations are considered the limits reduce by about 22-29% and increase by about 10-13%, respectively. (C) 2019 The Author(s). Published by Elsevier B.V

    Mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles in PbPb collisions at <tex>\sqrt{s_{NN}}$</tex>=2.76 and 5.02 TeV

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    Search for long-lived particles using nonprompt jets and missing transverse momentum with proton-proton collisions at root s=13 TeV

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    A search for long-lived particles decaying to displaced, nonprompt jets and missing transverse momentum is presented. The data sample corresponds to an integrated luminosity of 137 fb(-1) of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC in 2016-2018. Candidate signal events containing nonprompt jets are identified using the timing capabilities of the CMS electromagnetic calorimeter. The results of the search are consistent with the background prediction and are interpreted using a gauge-mediated supersymmetry breaking reference model with a gluino next-to-lightest supersymmetric particle. In this model, gluino masses up to 2100, 2500, and 1900 GeV are excluded at 95% confidence level for proper decay lengths of 0.3, 1, and 100 m, respectively. These are the best limits to date for such massive gluinos with proper decay lengths greater than similar to 0.5 m. (C) 2019 The Author. Published by Elsevier B.V

    Search for Higgs and Z boson decays to J/<tex>\psi</tex>orYpairsinthefourmuonfinalstateinprotonprotoncollisionsat<tex>s</tex> or Y pairs in the four-muon final state in proton-proton collisions at <tex>\sqrt{s}</tex>=13 TeV

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    Measurement of the <tex>t\bar{t}b\bar{b}$</tex> production cross section in the all-jet final state in pp collisions at 1as=13 TeV

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    Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at <tex>\sqrt{s_{NN}}$</tex>=5.02 TeV

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    Running of the top quark mass from proton-proton collisions at 1as=13 TeV

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