210 research outputs found

    Cell/Dendrite Distribution in Directionally Solidified Hypoeutectic Pb-Sb Alloys

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    The alloys Pb-2.2 wt pet Sb and Pb-5.8 wt pet Sb were directionally solidified with three different thermal gradients of 40, 86, and 140 K cm(-1) at growth rates ranging from 0.6 to 30 mu m s(-1). A Gaussian peak amplitude analysis of the cell/dendrite spacing distribution shows a distinct peak corresponding to the nearest neighbors. The peaks corresponding to the second and the third nearest neighbor spacings are also brought out by this technique. The ratios of the second to the first nearest neighbor spacings and that of the third to the first neighbor spacings are 1.85 +/-: 0.11 and 2.70 +/- 0.25, respectively. This indicates that the cells and dendrites both have a hexagonal distribution with a significant amount of superimposed noise. This is also confirmed by the frequency distribution of their number of nearest neighbors\u27 (coordination number)

    Search for narrow resonances in dilepton mass spectra in proton-proton collisions at root s=13 TeV and combination with 8 TeV data

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    Search for heavy gauge W ' bosons in events with an energetic lepton and large missing transverse momentum at root s=13TeV

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    Multiplicity and rapidity dependence of strange hadron production in pp, pPb, and PbPb collisions at the LHC

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    Measurement of B-s(0) meson production in pp and PbPb collisions at root S-NN=5.02 TeV

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    The production cross sections of B-s(0) mesons and charge conjugates are measured in proton-proton (pp) and PbPb collisions via the exclusive decay channel B-s(0)-> J/ psi phi ->mu(+) mu(-) K+K- at a center-of-mass energy of 5.02 TeV per nucleon pair and within the rapidity range vertical bar y vertical bar <2.4 using the CMS detector at the LHC. The pp measurement is performed as a function of transverse momentum (P-T) of the B-s(0), mesons in the range of 7 to 50 GeV/c and is compared to the predictions of perturbative QCD calculations. The B s production yield in PbPb collisions is measured in two F t intervals, 7 to 15 and 15 to 50 GeV/c, and compared to the yield in pp collisions in the same kinematic region. The nuclear modification factor (R-AA) is found to be 1.5 +/- 0.6(stat) +/- 0.5(syst) for 7-15 GeV/c, and 0.87 +/- 0.30(stat) +/- 0.1 7(syst) for 15-50 GeV/c, respectively. Within current uncertainties, the B-s(0) results are consistent with models of strangeness enhancement, and suppression by parton energy loss, as observed for the B+ mesons. Published by Elsevier B.V.Peer reviewe

    Charged-particle angular correlations in XeXe collisions at root s(NN)=5.44 TeV

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    Azimuthal correlations of charged particles in xenon-xenon collisions at a center-of-mass energy per nucleon pair of root s(NN) = 5.44 TeV are studied. The data were collected by the CMS experiment at the LHC with a total integrated luminosity of 3.42 mu b(-1). The collective motion of the system formed in the collision is parametrized by a Fourier expansion of the azimuthal particle density distribution. The azimuthal anisotropy coefficients v(2), v(3), and v(4) are obtained by the scalar-product, two-particle correlation, and multiparticle correlation methods. Within a hydrodynamic picture, these methods have different sensitivities to noncollective and fluctuation effects. The dependence of the Fourier coefficients on the size of the colliding system is explored by comparing the xenon-xenon results with equivalent lead-lead data. Model calculations that include initial-state fluctuation effects are also compared to the experimental results. The observed angular correlations provide new constraints on the hydrodynamic description of heavy ion collisions.Peer reviewe

    Observation of nuclear modifications in W-+/- boson production in pPb collisions at root s(NN)=8.16 TeV

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    The production of W-+/- bosons is studied in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of root s(NN) = 8.16 TeV. Measurements are performed in the W-+/- -> mu(+/-)nu(mu) channel using a data sample corresponding to an integrated luminosity of 173.4 +/- 6.1 nb(-1), collected by the CMS Collaboration at the LHC. The number of positively and negatively charged W bosons is determined separately in the muon pseudorapidity region in the laboratory frame vertical bar eta(mu)(lab)vertical bar 25 GeV/c. The W-+/- boson differential cross sections, muon charge asymmetry, and the ratios of W-+/- boson yields for the proton-going over the Pb-going beam directions are reported as a function of the muon pseudorapidity in the nucleon-nucleon centre-of-mass frame. The measurements are compared to the predictions from theoretical calculations based on parton distribution functions (PDFs) at next-to-leading-order. The results favour PDF calculations that include nuclear modifications and provide constraints on the nuclear PDF global fits. (C) 2019 The Author(s). Published by Elsevier B.V
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