388 research outputs found

    Search for New Physics with a Monojet and Missing Transverse Energy in pp Collisions at √s= 7 TeV

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    A study of events with missing transverse energy and an energetic jet is performed using pp collision data at a center-of-mass energy of 7 TeV. The data were collected by the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb-1. An excess of these events over standard model contributions is a signature of new physics such as large extra dimensions and unparticles. The number of observed events is in good agreement with the prediction of the standard model, and significant extension of the current limits on parameters of new physics benchmark models is achieved

    Search for charge-asymmetric production of W\u27 bosons in tt + jet events from pp collisions at √s = 7 TeV

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    A search is presented for charge-asymmetric production of a W\u27 boson that has been proposed to accommodate the forward–backward asymmetry observed in the production of top–antitop quark pairs at the Tevatron. The new heavy W\u27 boson would be produced in association with a top quark and would decay into top and down quarks. The data correspond to an integrated luminosity of 5.0 fb−1 in pp collisions at a center-of-mass energy of 7 TeV, recorded by the CMS detector at the LHC. No significant excess above the standard model expectations is observed, and, from a combination of the electron-plusjets and muon-plus-jets channels, a 95% confidence level lower limit of 840 GeV/c2 is set on the W\u27 boson mass for a W\u27 boson model with values for coupling constants to top and down quarks gL = 0 and gR = 2. In addition, a kinematic reconstruction of the W[1] resonance mass using the inherent charge asymmetry of this model finds no indication of the presence of W\u27 events in the data

    Measurement of the B0s Production Cross Section with B0s → J/ Decays in pp Collisions at √s = 7 TeV

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    The B0s differential production cross section is measured as functions of the transverse momentum and rapidity in pp collisions at √s= 7 TeV, using the B0s → J/UO decay, and compared with predictions based on perturbative QCD calculations at next-to-leading order. The data sample, collected by the CMS experiment at the LHC, corresponds to an integrated luminosity of 40 pb-1. The B0s is reconstructed from the decays J/U → µ+µ- and O→ K+K- The integrated B0s cross section times B0s→ J/UO branching fraction in the range 8BT\u3c 50 GeV/c and │yB \u3c 2.4 is measured to be 6.9 ± 0.6 ± 0.6 nb, where the first uncertainty is statistical and the second is systematic

    Study of W boson production in PbPb and pp collisions at √sNN = 2.76 TeV

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    A measurement is presented of W-boson production in PbPb collisions carried out at a nucleon–nucleon (NN) centre-of-mass energy √sNN of 2.76 TeV at the LHC using the CMS detector. In data corresponding to an integrated luminosity of 7.3 μb−1, the number of W → μνμ decays is extracted in the region of muon pseudorapidity |ημ| \u3c 2.1 and transverse momentum pμT \u3e 25 GeV/c. Yields of muons found per unit of pseudorapidity correspond to (159 ± 10(stat.) ± 12(syst.)) × 10−8 W+ and (154 ± 10(stat.) ± 12(syst.)) × 10−8 W− bosons per minimum-bias PbPb collision. The dependence of W production on the centrality of PbPb collisions is consistent with a scaling of the yield by the number of incoherent NN collisions. The yield of W bosons is also studied in a sample of pp interactions at √s = 2.76 TeV corresponding to an integrated luminosity of 231 nb−1. The individual W+ and W− yields in PbPb and pp collisions are found to agree, once the neutron and proton content in Pb nuclei is taken into account. Likewise, the difference observed in the dependence of the positive and negative muon production on pseudorapidity is consistent with next-to-leading-order perturbative QCD calculations

    Search for neutral Higgs bosons decaying to tau pairs in pp collisions at √s = 7 TeV

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    A search for neutral Higgs bosons decaying to tau pairs at a center-of-mass energy of 7 TeV is performed using a dataset corresponding to an integrated luminosity of 4.6 fb−1 recorded by the CMS experiment at the LHC. The search is sensitive to both the standard model Higgs boson and to the neutral Higgs bosons predicted by the minimal super symmetric extension of the standard model (MSSM). No excess of events is observed in the tau-pair invariant-mass spectrum. For a standard model Higgs boson in the mass range of 110–145 GeV upper limits at 95% confidence level (CL) on the production cross section are determined. We exclude a Higgs boson with mH = 115 GeV with a production cross section 3.2 times of that predicted by the standard model. In the MSSM, upper limits on the neutral Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, mA, sets stringent new bounds in the parameter space, excluding at 95% CL values of tan β as low as 7.1 at mA = 160 GeV in the mmaxh benchmark scenario
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