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A readout box prototype for the CMS Hadron Forward calorimeter upgrade was built and tested in the CERN H2 beamline. The prototype was designed to enable simultaneous tests of different readout options for the four anode upgrade PMTs, new front-end electronics design and new cabling. The response of the PMTs with different readout options was uniform and the background response was minimal. Multi-channel readout options further enhanced the background elimination. Passing all the electronic, mechanical and physics tests, the readout box proved to be capable of providing the forward hadron calorimeter operational requirements in the upgrade era.
[[abstract]]A comparison of the relative yields of Upsilon resonances in the mu(+)mu(-) decay channel in Pb-Pb and pp collisions at a center-of-mass energy per nucleon pair of 2.76 TeV is performed with data collected with the CMS detector at the LHC. Using muons of transverse momentum above 4 GeV/c and pseudorapidity below 2.4, the double ratio of the Upsilon(2S) and Upsilon(3S) excited states to the Upsilon(1S) ground state in Pb-Pb and pp collisions, [Upsilon(2S + 3S)/Upsilon(1S)](Pb-Pb) /[Upsilon 2S + 3S)/Upsilon(1S)](pp), is found to be 0.31(-0.15)(+0.19) (stat_ +/- 0.03(syst). The probability to obtain the measured value, or lower, if the true double ratio is unity, is calculated to be less than 1%.
[[abstract]]Measurements of the differential production cross sections d sigma/dp(T)(B) and d sigma/dy(B) for B(0) mesons produced in pp collisions at root s = 7 TeV are presented. The data set used was collected by the CMS experiment at the LHC and corresponds to an integrated luminosity of 40 pb(-1). The production cross section is measured from B(0) meson decays reconstructed in the exclusive final state J/psi K(S)(0), with the subsequent decays J psi -> mu(+)mu(-) and K(S)(0) -> pi(+)pi(-). The total cross section for p(T)(B) > 5 GeV and |y(B)| < 2: 2 is measured to be 33.2 +/- 2.5 +/- 3.5 mu b, where the first uncertainty is statistical and the second is systematic.
[[abstract]]A measurement of the lepton charge asymmetry in inclusive pp -> WX production at root s = 7TeV is presented based on data recorded by the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb(-1). This high precision measurement of the lepton charge asymmetry, performed in both the W -> e nu and W -> mu nu channels, provides new insights into parton distribution functions.
[[abstract]]First measurements of dihadron correlations for charged particles are presented for central PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV over a broad range in relative pseudorapidity (Delta eta) and the full range of relative azimuthal angle (Delta phi). The data were collected with the CMS detector, at the LHC. A broadening of the away-side (Delta phi approximate to pi) azimuthal correlation is observed at all Delta eta, as compared to the measurements in pp collisions. Furthermore, long-range dihadron correlations in Delta eta are observed for particles with similar phi values. This phenomenon, also known as the "ridge", persists up to at least vertical bar Delta eta vertical bar = 4. For particles with transverse momenta (p(T)) of 2-4 GeV/c, the ridge is found to be most prominent when...
[[abstract]]The t (t) over bar production cross section and top quark mass are measured in proton-proton collisions at root s = 7 TeV in a data sample corresponding to an integrated luminosity of 36 pb(-1) collected by the CMS experiment. The measurements are performed in events with two leptons (electrons or muons) in the final state. Results of the cross section measurement in events with and without b-quark identification are obtained and combined. The measured value is sigma(tt) - 168 +/- 18 (stat:) +/- 14 (syst:) +/- 7 (lumi:) pb, consistent with predictions from the standard model. The top quark mass m(top) is reconstructed with two different methods, a full kinematic analysis and a matrix weighting technique. The combination yields a measurement of m(top) = 175.5 +/- 4.6 (stat:) +/- 4: 6 (syst:) GeV/c(2).
[[abstract]]A measurement of the double-differential inclusive dijet production cross section in proton-proton collisions at root s = 7 TeV is presented as a function of the dijet invariant mass and jet rapidity. The data correspond to an integrated luminosity of 36 pb(-1), recorded with the CMS detector at the LHC. The measurement covers the dijet mass range 0.2 TeV to 3.5 TeV and jet rapidities up to vertical bar y vertical bar = 2.5. It is found to be in good agreement with next-to-leading-order QCD predictions. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.
[[abstract]]A measurement of W(+)W(-) production in pp collisions at root s = 7 TeV and a search for the Higgs boson are reported. The W(+)W(-) candidates are selected in events with two leptons, either electrons or muons. The measurement is performed using LHC data recorded with the CMS detector, corresponding to an integrated luminosity of 36 pb(-1). The pp -> W(+)W(-) cross section is measured to be 41.1 +/- 15.3 (stat) +/- 5.8 (syst) +/- 4.5 (lumi) ph. consistent with the standard model prediction. Limits on WW gamma and WWZ anomalous triple gauge couplings are set. The search for the standard model Higgs boson in the W(+)W(-) decay mode does not reveal any evidence of excess above backgrounds. Limits are set on the production of the Higgs boson in the context of the standard model and in the presence of a sequential fourth family ...
[[abstract]]A first measurement of the polarization of W bosons with large transverse momenta in pp collisions is presented. The measurement is based on 36 pb(-1) of data recorded at root s = 7 TeV by the CMS detector at the LHC. The left-handed, right-handed, and longitudinal polarization fractions (f(L), f(R), and f(0), respectively) of W bosons with transverse momenta larger than 50 GeV are determined by using decays to both electrons and muons. The muon final state yields the most precise measurement: (f(L) - f(R))(-) = 0.240 +/- 0.036(syst) +/- 0.031(syst) and f(0)(-) = 0.183 +/- 0.087(stat) +/- 0.123(syst) for negatively charged W bosons and (f(L) - f(R))(+) = 0.310 +/- 0.036(syst) +/- 0.017(syst) and f(0)(+) = 0.171 +/- 0.085(syst) +/- 0.099(syst) for positively charged W bosons. This establishes, for the first time, that W boso...
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