Combined Tevatron upper limit on gg→H→W+W- and constraints on the Higgs boson mass in fourth-generation fermion models
Physical Review D - Particles, Fields, Gravitation and Cosmology 82:1 (2010)
Abstract:
We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg→H→W+W - in pp̄ collisions at the Fermilab Tevatron Collider at √s=1.96TeV. With 4.8fb-1 of integrated luminosity analyzed at CDF and 5.4fb-1 at D0, the 95% confidence level upper limit on σ(gg→H)×B(H→W+W-) is 1.75 pb at mH=120GeV, 0.38 pb at mH=165GeV, and 0.83 pb at mH=200GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV. © 2010 The American Physical Society.First measurement of Bose-Einstein correlations in proton-proton collisions at √s=0.9 and 2.36 TeV at the LHC
Physical Review Letters 105:3 (2010)
Abstract:
Bose-Einstein correlations have been measured using samples of proton-proton collisions at 0.9 and 2.36 TeV center-of-mass energies, recorded by the CMS experiment at the CERN Large Hadron Collider. The signal is observed in the form of an enhancement of pairs of same-sign charged particles with small relative four-momentum. The size of the correlated particle emission region is seen to increase significantly with the particle multiplicity of the event.Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at √s=7TeV
Physical Review Letters 105:2 (2010)
Abstract:
Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at √s=7TeV are measured with the inner tracking system of the CMS detector at the LHC. The charged-hadron yield is obtained by counting the number of reconstructed hits, hit pairs, and fully reconstructed charged-particle tracks. The combination of the three methods gives a charged-particle multiplicity per unit of pseudorapidity dNch/ dη|η|<0.5 = 5.78 ± 0.01(stat)±0.23(syst) for non-single-diffractive events, higher than predicted by commonly used models. The relative increase in charged-particle multiplicity from √s=0.9 to 7 TeV is [66.1±1.0(stat)±4.2(syst)]%. The mean transverse momentum is measured to be 0.545±0.005(stat)±0.015(syst)GeV/c. The results are compared with similar measurements at lower energies. © 2010 The American Physical Society.Measurement of the ratio σ{tt}/σ{Z/γ{*}→ll} and precise extraction of the tt cross section.
Phys Rev Lett 105:1 (2010) 012001
Abstract:
We report a measurement of the ratio of the tt to Z/γ{*} production cross sections in sqrt[s]=1.96 TeV pp collisions using data corresponding to an integrated luminosity of up to 4.6 fb{-1}, collected by the CDF II detector. The tt cross section ratio is measured using two complementary methods, a b-jet tagging measurement and a topological approach. By multiplying the ratios by the well-known theoretical Z/γ{*}→ll cross section predicted by the standard model, the extracted tt cross sections are effectively insensitive to the uncertainty on luminosity. A best linear unbiased estimate is used to combine both measurements with the result σ{tt}=7.70±0.52 pb, for a top-quark mass of 172.5 GeV/c{2}.Erratum: Measurement of the W+W- production cross section and search for anomalous WWγ and WWZ couplings in pp̄ collisions at √s=1.96 TeV (Phys. Rev. Lett. (2010) 104 (201801))
Physical Review Letters 105:1 (2010)