A measurement of the tt production cross section in proton-proton collisions at a centre-of-mass ... more A measurement of the tt production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 pb −1 and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the tt signal from W+jets and QCD multijet background events. The measured cross section is 173 +39 −32 (stat. + syst.) pb, consistent with standard model expectations.
We present a measurement of the ratio of positive to negative muon fluxes from cosmic ray interac... more We present a measurement of the ratio of positive to negative muon fluxes from cosmic ray interactions in the atmosphere, using data collected by the CMS detector both at ground level and in the underground experimental cavern at the CERN LHC. Muons were detected in the momentum range from 5 GeV/c to 1 TeV/c. The surface flux ratio is measured to be 1.2766 ± 0.0032 (stat.) ± 0.0032 (syst.), independent of the muon momentum, below 100 GeV/c. This is the most precise measurement to date. At higher momenta the data are consistent with an increase of the charge ratio, in agreement with cosmic ray shower models and compatible with previous measurements by deep-underground experiments.
The production of J/ψ mesons is studied in pp collisions at \(\sqrt{s} = 7\) TeV with the CMS ex... more The production of J/ψ mesons is studied in pp collisions at \(\sqrt{s} = 7\) TeV with the CMS experiment at the LHC. The measurement is based on a dimuon sample corresponding to an integrated luminosity of 314 nb−1. The J/ψ differential cross section is determined, as a function of the J/ψ transverse momentum, in three rapidity ranges. A fit to the decay length distribution is used to separate the prompt from the non-prompt (b hadron to J/ψ) component. Integrated over J/ψ transverse momentum from 6.5 to 30 GeV/c and over rapidity in the range |y|ψ mesons assuming unpolarized production and 26.0±1.4(stat.)±1.6(syst.)±2.9(luminosity) nb for J/ψ mesons from b-hadron decays.
Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are... more Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at √ s = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between −2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN ch /dη| |η|<0.5 , are 3.48 ± 0.02 (stat.) ± 0.13 (syst.) and 4.47 ± 0.04 (stat.) ± 0.16 (syst.), respectively. The results at 0.9 TeV are in agreement with previous measurements and confirm the expectation of near equal hadron production in pp and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date.
A measurement of inclusive W and Z production cross sections in pp collisions at √ s = 7 TeV is p... more A measurement of inclusive W and Z production cross sections in pp collisions at √ s = 7 TeV is presented. The electron and muon decay channels are analyzed in a data sample collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb −1 . The measured inclusive cross sections are σ(pp → WX) × B(W → ν) = 10.30 ± 0.02 (stat.) ± 0.10 (syst.) ± 0.10 (th.) ± 0.41 (lumi.) nb and σ(pp → ZX) × B(Z → + − ) = 0.974 ± 0.007 (stat.) ± 0.007 (syst.) ± 0.018 (th.) ± 0.039 (lumi.) nb, limited to the dilepton invariant mass range 60 to 120 GeV. The luminosity-independent cross section ratios are (σ(pp
Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are... more Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at \(\sqrt{s} = 0.9 \) and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between --2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN ch/dη||η|\( \overline p p \) and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date.
A measurement of the tt production cross section in proton-proton collisions at a centre-of-mass ... more A measurement of the tt production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 pb −1 and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the tt signal from W+jets and QCD multijet background events. The measured cross section is 173 +39 −32 (stat. + syst.) pb, consistent with standard model expectations.
We present a measurement of the ratio of positive to negative muon fluxes from cosmic ray interac... more We present a measurement of the ratio of positive to negative muon fluxes from cosmic ray interactions in the atmosphere, using data collected by the CMS detector both at ground level and in the underground experimental cavern at the CERN LHC. Muons were detected in the momentum range from 5 GeV/c to 1 TeV/c. The surface flux ratio is measured to be 1.2766 ± 0.0032 (stat.) ± 0.0032 (syst.), independent of the muon momentum, below 100 GeV/c. This is the most precise measurement to date. At higher momenta the data are consistent with an increase of the charge ratio, in agreement with cosmic ray shower models and compatible with previous measurements by deep-underground experiments.
The production of J/ψ mesons is studied in pp collisions at \(\sqrt{s} = 7\) TeV with the CMS ex... more The production of J/ψ mesons is studied in pp collisions at \(\sqrt{s} = 7\) TeV with the CMS experiment at the LHC. The measurement is based on a dimuon sample corresponding to an integrated luminosity of 314 nb−1. The J/ψ differential cross section is determined, as a function of the J/ψ transverse momentum, in three rapidity ranges. A fit to the decay length distribution is used to separate the prompt from the non-prompt (b hadron to J/ψ) component. Integrated over J/ψ transverse momentum from 6.5 to 30 GeV/c and over rapidity in the range |y|ψ mesons assuming unpolarized production and 26.0±1.4(stat.)±1.6(syst.)±2.9(luminosity) nb for J/ψ mesons from b-hadron decays.
Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are... more Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at √ s = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between −2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN ch /dη| |η|<0.5 , are 3.48 ± 0.02 (stat.) ± 0.13 (syst.) and 4.47 ± 0.04 (stat.) ± 0.16 (syst.), respectively. The results at 0.9 TeV are in agreement with previous measurements and confirm the expectation of near equal hadron production in pp and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date.
A measurement of inclusive W and Z production cross sections in pp collisions at √ s = 7 TeV is p... more A measurement of inclusive W and Z production cross sections in pp collisions at √ s = 7 TeV is presented. The electron and muon decay channels are analyzed in a data sample collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb −1 . The measured inclusive cross sections are σ(pp → WX) × B(W → ν) = 10.30 ± 0.02 (stat.) ± 0.10 (syst.) ± 0.10 (th.) ± 0.41 (lumi.) nb and σ(pp → ZX) × B(Z → + − ) = 0.974 ± 0.007 (stat.) ± 0.007 (syst.) ± 0.018 (th.) ± 0.039 (lumi.) nb, limited to the dilepton invariant mass range 60 to 120 GeV. The luminosity-independent cross section ratios are (σ(pp
Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are... more Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at \(\sqrt{s} = 0.9 \) and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between --2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN ch/dη||η|\( \overline p p \) and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date.
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