171 research outputs found

    Observation of Charge-Dependent Azimuthal Correlations in p-Pb Collisions and Its Implication for the Search for the Chiral Magnetic Effect

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    Pseudorapidity distributions of charged hadrons in proton-lead collisions at root s(NN)=5:02 and 8.16 TeV

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    The pseudorapidity distributions of charged hadrons in proton-lead collisions at nucleon-nucleon center-of-mass energies root s(NN) = 5.02 and 8.16 TeV are presented. The measurements are based on data samples collected by the CMS experiment at the LHC. The number of primary charged hadrons produced in non-single-diffractive proton-lead collisions is determined in the pseudorapidity range vertical bar eta(lab)vertical bar vertical bar(vertical bar eta cm vertical bar) <0.5 are 17.1 +/- 0.01 (stat) +/- 0.59 (syst) and 20.10 +/- 0.01 (stat) +/- 0.5(syst) at root s(NN) = 5.02 and 8.16 TeV, respectively. The particle densities per participant nucleon are compared to similar measurements in proton-proton, proton-nucleus, and nucleus-nucleus collisions.Peer reviewe

    Search for Resonant Production of High-Mass Photon Pairs in Proton-Proton Collisions at root s=8 and 13 TeV

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    Search for high mass dijet resonances with a new background prediction method in proton-proton collisions at &#8730;s = 13 TeV

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    Search for Pair-Produced Resonances Each Decaying into at Least Four Quarks in Proton-Proton Collisions at root s=13 TeV

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    This Letter presents the results of a search for pair-produced particles of masses above 100 GeV that each decay into at least four quarks. Using data collected by the CMS experiment at the LHC in 2015-2016, corresponding to an integrated luminosity of 38.2 fb(-1), reconstructed particles are clustered into two large jets of similar mass, each consistent with four-parton substructure. No statistically significant excess of data over the background prediction is observed in the distribution of average jet mass. Pair-produced squarks with dominant hadronic R-parity-violating decays into four quarks and with masses between 0.10 and 0.72 TeV are excluded at 95% confidence level. Similarly, pair-produced gluinos that decay into five quarks are also excluded with masses between 0.10 and 1.41 TeV at 95% confidence level. These are the first constraints that have been placed on pair-produced particles with masses below 400 GeV that decay into four or five quarks, bridging a significant gap in the coverage of R-parity-violating supersymmetry parameter space.Peer reviewe

    Measurement of the WZ production cross section in pp collisions at root s=7 and 8 TeV and search for anomalous triple gauge couplings at root s=8 TeV

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    Measurement of b hadron lifetimes in pp collisions at root s=8TeV

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    Correction: DOI:10.1140/epjc/s10052-018-6014-7Measurements are presented of the lifetimes of the B-0, B-s(0), Lambda(0)(b), and B-c(+) hadrons using the decay channels B-0 -> J/psi K*(892)(0), B-0 -> J/psi K-S(0), B-s(0) -> J/psi pi(+)pi(-), B-s(0) -> J/psi phi(1020), Lambda(0)(b) -> J/psi Lambda(0), and B-c(+) -> J/psi pi(+). The data sample, corresponding to an integrated luminosity of 19.7 fb(-1), was collected by the CMS detector at the LHC in proton-proton collisions at root s = 8TeV. The B-0 life-time is measured to be 453.0 +/- 1.6 (stat) +/- 1.8 (syst) mu m in J/psi K*(892)(0) and 457.8 +/- 2.7 (stat) +/- 2.8 (syst) mu m in J/psi K-S(0), which results in a combined measurement of c tau(0) = 454.1 +/- 1.4 (stat) +/- 1.7 (syst) mu m. The effective lifetime of the B-s(0) meson is measured in two decay modes, with contributions from different amounts of the heavy and light eigenstates. This results in two different measured lifetimes: c tau(0)(Bs) -> J/psi pi(+)pi(-) = 502.7 +/- 10.2 (stat) +/- 3.4 (syst) mu m and c tau(0)(Bs) -> J/psi phi(1020) = 443.9 +/- 2.0 (stat) +/- 1.5 (syst) mu m. The Lambda(0)(b) lifetime is found to be 442.9 +/- 8.2 (stat) +/- 2.8 (syst) mu m. The precision from each of these channels is as good as or better than previous measurements. The B-c(+) lifetime, measured with respect to the B+ to reduce the systematic uncertainty, is 162.3 +/- 7.8 (stat) +/- 4.2 (syst) +/- 0.1 (tau(B+)) mu m. All results are in agreement with current world-average values.Peer reviewe

    Measurement of dijet azimuthal decorrelation in pp collisions at root s=8 TeV

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    Upsilon (nS) polarizations versus particle multiplicity in pp collisions at root s=7 TeV

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    Search for Zγ resonances using leptonic and hadronic final states in proton-proton collisions at √s=13 TeV

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    A search is presented for resonances decaying to a Z boson and a photon. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1, and collected with the CMS detector at the LHC in 2016. Two decay modes of the Z boson are investigated. In the leptonic channels, the Z boson candidates are reconstructed using electron or muon pairs. In the hadronic channels, they are identified using a large-radius jet, containing either light-quark or b quark decay products of the Z boson, via jet substructure and advanced b quark tagging techniques. The results from these channels are combined and interpreted in terms of upper limits on the product of the production cross section and the branching fraction to Zγ for narrow and broad spin-0 resonances with masses between 0.35 and 4.0 TeV, providing thereby the most stringent limits on such resonances.[Figure not available: see fulltext.]
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