Browsing by Author "Cuplov, V."

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    Azimuthal Anisotropy of Charged Particles at High Transverse Momenta in Pb-Pb Collisions at √sNN=2.76  TeV
    (American Physical Society, 2012) Adair, A.; Boulahouache, C.; Cuplov, V.; Ecklund, K.M.; Geurts, F.J.M.; Padley, B.P.; Redjimi, R.; Roberts, J.; Zabel, J.
    The azimuthal anisotropy of charged particles in Pb-Pb collisions at √sNN=2.76  TeV is measured with the CMS detector at the LHC over an extended transverse momentum (pT) range up to approximately 60  GeV/c. The data cover both the low-pT region associated with hydrodynamic flow phenomena and the high-pT region where the anisotropies may reflect the path-length dependence of parton energy loss in the created medium. The anisotropy parameter (v2) of the particles is extracted by correlating charged tracks with respect to the event-plane reconstructed by using the energy deposited in forward-angle calorimeters. For the six bins of collision centrality studied, spanning the range of 0–60% most-central events, the observed v2 values are found to first increase with pT, reaching a maximum around pT=3  GeV/c, and then to gradually decrease to almost zero, with the decline persisting up to at least pT=40  GeV/c over the full centrality range measured.
  • Thumbnail Image
    Item
    Combined results of searches for the standard model Higgs boson in pp collisions at √s = 7 TeV
    (Elsevier, 2012) Adair, A.; Boulahouache, C.; Cuplov, V.; Ecklund, K.M.; Geurts, F.J.M.; Padley, B.P.; Redjimi, R.; Roberts, J.; Zabel, J.
    Combined results are reported from searches for the standard model Higgs boson in proton–proton collisions at √s=7 TeV in five Higgs boson decay modes: γγ, bb, ττ, WW, and ZZ. The explored Higgs boson mass range is 110–600 GeV. The analysed data correspond to an integrated luminosity of 4.6–4.8 fb−1. The expected excluded mass range in the absence of the standard model Higgs boson is 118–543 GeV at 95% CL. The observed results exclude the standard model Higgs boson in the mass range 127-600 GeV at 95% CL, and in the mass range 129–525 GeV at 99% CL. An excess of events above the expected standard model background is observed at the low end of the explored mass range making the observed limits weaker than expected in the absence of a signal. The largest excess, with a local significance of 3.1σ, is observed for a Higgs boson mass hypothesis of 124 GeV. The global significance of observing an excess with a local significance ⩾3.1σ anywhere in the search range 110–600 (110–145) GeV is estimated to be 1.5σ(2.1σ). More data are required to ascertain the origin of the observed excess
  • Thumbnail Image
    Item
    Erratum: Search for anomalous t¯t production in the highly-boosted all-hadronic final state
    (Springer, 2014) Adair, A.; Boulahouache, C.; Cuplov, V.; Ecklund, K.M.; Geurts, F.J.M.; Padley, B.P.; Redjimi, R.; Roberts, J.; Zabel, J.
  • Thumbnail Image
    Item
    Search for Dark Matter and Large Extra Dimensions in pp Collisions Yielding a Photon and Missing Transverse Energy
    (American Physical Society, 2012) Adair, A.; Boulahouache, C.; Cuplov, V.; Ecklund, K.M.; Geurts, F.J.M.; Padley, B.P.; Redjimi, R.; Roberts, J.; Zabel, J.
    Results are presented from a search for new physics in the final state containing a photon (γ) and missing transverse energy (E̸T). The data correspond to an integrated luminosity of 5.0  fb−1 collected in pp collisions at √s=7  TeV by the CMS experiment. The observed event yield agrees with standard-model expectations for the γ+E̸T events. Using models for the production of dark-matter particles (χ), we set 90% confidence level (C.L.) upper limits of 13.6–15.4 fb on χ production in the γ+E̸T state. These provide the most sensitive upper limits for spin-dependent χ-nucleon scattering for χ masses (Mχ) between 1 and 100 GeV. For spin-independent contributions, the present limits are extended to Mχ<3.5  GeV. For models with 3–6 large extra dimensions, our data exclude extra-dimensional Planck scales between 1.64 and 1.73 TeV at 95% C.L.
  • Thumbnail Image
    Item
    Search for New Physics with Same-Sign Isolated Dilepton Events with Jets and Missing Transverse Energy
    (American Physical Society, 2012) Adair, A.; Boulahouache, C.; Cuplov, V.; Ecklund, K.M.; Geurts, F.J.M.; Padley, B.P.; Redjimi, R.; Roberts, J.; Zabel, J.
    A search for new physics is performed in events with two same-sign isolated leptons, hadronic jets, and missing transverse energy in the final state. The analysis is based on a data sample corresponding to an integrated luminosity of 4.98  fb−1 produced in pp collisions at a center-of-mass energy of 7 TeV collected by the CMS experiment at the LHC. This constitutes a factor of 140 increase in integrated luminosity over previously published results. The observed yields agree with the standard model predictions and thus no evidence for new physics is found. The observations are used to set upper limits on possible new physics contributions and to constrain supersymmetric models. To facilitate the interpretation of the data in a broader range of new physics scenarios, information on the event selection, detector response, and efficiencies is provided.
  • Thumbnail Image
    Item
    Search for Signatures of Extra Dimensions in the Diphoton Mass Spectrum at the Large Hadron Collider
    (American Physical Society, 2012) Adair, A.; Boulahouache, C.; Cuplov, V.; Ecklund, K.M.; Geurts, F.J.M.; Padley, B.P.; Redjimi, R.; Roberts, J.; Zabel, J.
    A search for signatures of extra spatial dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at √s=7  TeV corresponding to an integrated luminosity of 2.2  fb−1. In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3–3.8 TeV at the 95% confidence level. These limits are the most restrictive bounds on virtual-graviton exchange to date. The most restrictive lower limits to date are also set on the mass of the first graviton excitation in the Randall-Sundrum model in the range of 0.86–1.84 TeV, for values of the associated coupling parameter between 0.01 and 0.10.
  • Thumbnail Image
    Item
    Search for the Standard Model Higgs Boson in the Decay Channel H→ZZ→4l in pp Collisions at √s=7  TeV
    (American Physical Society, 2012) Adair, A.; Boulahouache, C.; Cuplov, V.; Ecklund, K.M.; Geurts, F.J.M.; Padley, B.P.; Redjimi, R.; Roberts, J.; Zabel, J.
    A search for a Higgs boson in the four-lepton decay channel H→ZZ, with each Z boson decaying to an electron or muon pair, is reported. The search covers Higgs boson mass hypotheses in the range of 110100  GeV (with 13 below 160 GeV), while 67.1±6.0 (9.5±1.3) events are expected from background. The four-lepton mass distribution is consistent with the expectation of standard model background production of ZZ pairs. Upper limits at 95% confidence level exclude the standard model Higgs boson in the ranges of 134–158 GeV, 180–305 GeV, and 340–465 GeV. Small excesses of events are observed around masses of 119, 126, and 320 GeV, making the observed limits weaker than expected in the absence of a signal.