36 research outputs found

    Pion production in proton collisions with light nuclei: implications for atmospheric neutrinos

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    Differences among calculations of the atmospheric neutrino beam can be traced in large part to differences in the representation of pion production by protons interacting with nuclei in the atmosphere. In this paper we review the existing data with the goal of determining the regions of phase space in which new measurements could help to improve the input to the calculations.Comment: latex, 13 pages, 6 figure

    Event activity dependence of Y (nS) production in √sNN = 5.02 TeV pPb and √s = 2.76 TeV pp collisions

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    Measurement of the cross section for electroweak production of a Z boson, a photon and two jets in proton-proton collisions at s \sqrt{\mathrm{s}} = 13 TeV and constraints on anomalous quartic couplings

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    Search for lepton flavour violating decays of a neutral heavy Higgs boson to Ότ and eτ in proton-proton collisions at √s = 13 TeV

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    A search for lepton flavour violating decays of a neutral non-standard-model Higgs boson in the Ότ and eτ decay modes is presented. The search is based on proton-proton collisions at a center of mass energy √s = 13 TeV collected with the CMS detector in 2016, corresponding to an integrated luminosity of 35.9 fb⁻Âč. The τ leptons are reconstructed in the leptonic and hadronic decay modes. No signal is observed in the mass range 200–900 GeV. At 95% confidence level, the observed (expected) upper limits on the production cross section multiplied by the branching fraction vary from 51.9 (57.4) fb to 1.6 (2.1) fb for the Ότ and from 94.1 (91.6) fb to 2.3 (2.3) fb for the eτ decay modes

    Observation of Single Top Quark Production in Association with a Z Boson in Proton-Proton Collisions at root s=13 TeV

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    The observation of single top quark production in association with a Z boson and a quark (tZq) is reported. Events from proton-proton collisions at a center-of-mass energy of 13 TeV containing three charged leptons (either electrons or muons) and at least two jets are analyzed. The data were collected with the CMS detector in 2016 and 2017 and correspond to an integrated luminosity of 77.4fb(-1). The increased integrated luminosity, a multivariate lepton identification, and a redesigned analysis strategy improve significantly the sensitivity of the analysis compared to previous searches for tZq production. The tZq signal is observed with a significance well over 5 standard deviations. The measured tZq production cross section is sigma(pp -> tZq -> tl(+) l(-) q) = 111 +/- 13 (stat)(-9)(+11) (syst) fb, for dilepton invariant masses above 30 GeV, in agreement with the standard model expectation

    Measurement of the cross section for electroweak production of a Z boson, a photon and two jets in proton-proton collisions at √s = 13 TeV and constraints on anomalous quartic couplings

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    A measurement is presented of the cross section for electroweak production of a Z boson and a photon in association with two jets (ZÎłjj) in proton-proton collisions. The Z boson candidates are selected through their decay into a pair of electrons or muons. The process of interest, electroweak ZÎłjj production, is isolated by selecting events with a large dijet mass and a large pseudorapidity gap between the two jets. The measurement is based on data collected at the CMS experiment at √s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb⁻Âč. The observed significance of the signal is 3.9 standard deviations, where a significance of 5.2 standard deviations is expected in the standard model. These results are combined with published results by CMS at √s = 8 TeV, which leads to observed and expected respective significances of 4.7 and 5.5 standard deviations. From the 13 TeV data, a value is obtained for the signal strength of electroweak ZÎłjj production and bounds are given on quartic vector boson interactions in the framework of dimension-eight effective field theory operators

    Measurement of properties of Bs0 {\mathrm{B}}_{\mathrm{s}}^0 → ÎŒ+Ό− decays and search for B⁰→ ÎŒâșΌ⁻ with the CMS experiment

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    Measurement of top quark pair production in association with a Z boson in proton-proton collisions at s \sqrt{\mathrm{s}} = 13 TeV

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    A measurement of the inclusive cross section of top quark pair production in association with a Z boson using proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC is performed. The data sample corresponds to an integrated luminosity of 77.5 fb−1, collected by the CMS experiment during 2016 and 2017. The measurement is performed using final states containing three or four charged leptons (electrons or muons), and the Z boson is detected through its decay to an oppositely charged lepton pair. The production cross section is measured to be σ(tt ÂŻ Z ttÂŻZ ) = 0.95 ± 0.05 (stat) ± 0.06 (syst) pb. For the first time, differential cross sections are measured as functions of the transverse momentum of the Z boson and the angular distribution of the negatively charged lepton from the Z boson decay. The most stringent direct limits to date on the anomalous couplings of the top quark to the Z boson are presented, including constraints on the Wilson coefficients in the framework of the standard model effective field theory
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