17 research outputs found

    Measurement of the jet mass in highly boosted t(t)over-bar events from pp collisions at root s=8TeV

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    Search for associated production of a Z boson with a single top quark and for tZ flavour-changing interactions in pp collisions at root s=8 TeV

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    A search for the production of a single top quark in association with a Z boson is presented, both to identify the expected standard model process and to search for flavour-changing neutral current interactions. The data sample corresponds to an integrated luminosity of 19.7 fb−1 recorded by the CMS experiment at the LHC in proton-proton collisions at s√=8s=8 TeV. Final states with three leptons (electrons or muons) and at least one jet are investigated. An events yield compatible with tZq standard model production is observed, and the corresponding cross section is measured to be σ(pp → tZq → ℓνbℓ+ℓ−q) = 10− 7+ 8 fb with a significance of 2.4 standard deviations. No presence of flavour-changing neutral current production of tZq is observed. Exclusion limits at 95% confidence level on the branching fractions of a top quark decaying to a Z boson and an up or a charm quark are found to be ℬ(t → Zu) < 0.022% and ℬ(t → Zc) < 0.049%

    Rating Health and Social Indicators for Use with Indigenous Communities: A Tool for Balancing Cultural and Scientific Utility

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    Community participation, Health status indicators, Indigenous populations, Reliability and validity, Programme planning,

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

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    A search for the resonant production of high-mass photon pairs is presented. The search focuses on spin-0 and spin-2 resonances with masses between 0.5 and 4.5 TeV, and with widths, relative to the mass, between 1.4 x 10(-4) and 5.6 x 10(-2). The data sample corresponds to an integrated luminosity of 12.9 fb(-1) of proton-proton collisions collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV. No significant excess is observed relative to the standard model expectation. The results of the search are combined statistically with those previously obtained in 2012 and 2015 at root s = 8 and 13 TeV, respectively, corresponding to integrated luminosities of 19.7 and 3.3 fb(-1), to derive exclusion limits on scalar resonances produced through gluon-gluon fusion, and on Randall-Sundrum gravitons. The lower mass limits for Randall-Sundrum gravitons range from 1.95 to 4.45 TeV for coupling parameters between 0.01 and 0.2. These are the most stringent limits on Randall-Sundrum graviton production to date. (C) 2017 The Author. Published by Elsevier B.V

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

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    The cross section for coherent J/psi photoproduction accompanied by at least one neutron on one side of the interaction point and no neutron activity on the other side, Xn0n, is measured with the CMS experiment in ultra-peripheral PbPb collisions at root sNN= 2.76TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 159 mu b(-1), collected during the 2011 PbPb run. The J/psi mesons are reconstructed in the dimuon decay channel, while neutrons are detected using zero degree calorimeters. The measured cross section is d sigma(Xn)o(n)(coh)/dy(J/psi) = 0.36 +/- 0.04 (stat)+/- 0.04 (syst) mbin the rapidity interval 1.8 <vertical bar y vertical bar < 2.3. Using a model for the relative rate of coherent photoproduction processes, this Xn0nmeasurement gives a total coherent photoproduction cross section of d sigma(coh/) dy(J/psi) = 1.82 +/- 0.22 (stat)+/- 0.20 (syst)+/- 0.19 (theo) mb. The data strongly disfavorthe impulse approximation model prediction, indicating that nuclear effects are needed to describe coherent J/psi photoproduction in.+ Pbinteractions. The data are found to be consistent with the leading twist approximation, which includes nuclear gluon shadowing. (C) 2017 The Author(s). Published by Elsevier B.V

    Observation of gamma(1S) pair production in proton-proton collisions at root s=8 TeV

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    Measurement of the differential inclusive B+ hadron cross sections in pp collisions at root s=13TeV

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    The differential cross sections for inclusive production of B+ hadrons are measured as a function of the B+ transverse momentum p(T)(B) and rapidity y(B) in pp collisions at a centre-of-mass energy of 13 TeV, using data collected by the CMS experiment that correspond to an integrated luminosity of 48.1 pb(-1). The measurement uses the exclusive decay channel B+ -> J/psi K+, with J/psi mesons that decay to a pair of muons. The results show a reasonable agreement with theoretical calculations within the uncertainties. (C) 2017 The Author(s). Published by Elsevier B.V
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