713 research outputs found

    CMS: minimum bias studies

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    The early data from LHC will allow the first look at minimum bias p-p collisions initially at the center-of-mass energies of 10 and later 14 TeV. The plans of the CMS collaboration to measure cross sections and differential yields of charged particles (unidentified or identified) and neutrals produced in inelastic p-p collisions at 14 TeV are presented. The tracking of charged particles will be possible down to about 100 MeV/c, with good efficiency and negligible fake rate. The yield of charged kaons and protons can be extracted for total momenta below 0.8 and 1.5 GeV/c, respectively. Comparisons of the results to theoretical models are also discussed

    Top-quark production in proton-nucleus and nucleus-nucleus collisions at LHC energies and beyond

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    Single and pair top-quark production in proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the CERN Large Hadron Collider (LHC) and Future Circular Collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to sigma(t (t) over bar) = 3.4 mu b in Pb-Pb at root s(NN) = 5.5 TeV, and sigma(t (t) over bart) = 60 nb in p-Pb at root s(NN) = 8.8 TeV. At the FCC energies of root s(NN) = 39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state t (t) over bar --> W(+)b W-(b) over bar --> b (b) over bar ll nu nu with l = e(+/-), mu(+/-), after typical acceptance and efficiency cuts, one expects about 90 and 300 top-quarks per nominal LHC-year and 4.7 . 10(4) and 10(5) per FCC-year in Pb-Pb and p-Pb collisions respectively. The total t (t) over bar cross sections, dominated by gluon fusion processes, are enhanced by 3-8% in nuclear compared to p-p collisions due to an overall net gluon antishadowing, although different regions of their differential distributions are depleted due to shadowing or EMC-effect corrections. The rapidity distributions of the decay leptons in t (t) over bar processes can be used to reduce the uncertainty on the Pb gluon density at high virtualities by up to 30% at the LHC (full heavy-ion programme), and by 70% per FCC-year. The cross sections for single-top production in electroweak processes are also computed, yielding about a factor of 30 smaller number of measurable top-quarks after cuts, per system and per year. (C) 2015 The Authors. Published by Elsevier B.V.Peer reviewe

    Measurement of the transverse momentum spectrum of the Higgs boson produced in pp collisions at ‚ąös=8 TeV using H ‚Üí WW decays

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    The cross section for Higgs boson production in pp collisions is studied using the H ‚Üí W[superscript +]W[superscript ‚ąí] decay mode, followed by leptonic decays of the W bosons to an oppositely charged electron-muon pair in the final state. The measurements are performed using data collected by the CMS experiment at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.4 fb[superscript ‚ąí1]. The Higgs boson transverse momentum (p[subscript T]) is reconstructed using the lepton pair p[subscript T] and missing p[subscript T]. The differential cross section times branching fraction is measured as a function of the Higgs boson pTin a fiducial phase space defined to match the experimental acceptance in terms of the lepton kinematics and event topology. The production cross section times branching fraction in the fiducial phase space is measured to be 39 ¬Ī 8 (stat) ¬Ī 9 (syst) fb. The measurements are found to agree, within experimental uncertainties, with theoretical calculations based on the standard model. Keywords: Hadron-Hadron scattering (experiments), Higgs physicsNational Science Foundation (U.S.)United States. Department of Energ

    Differential cross section measurements for the production of a W boson in association with jets in proton‚Äďproton collisions at ‚ąös = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript ‚ąí1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an