Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (η) and azimuthal angle (ϕ). Short-range correlations in Δη, which are studied in minimum bias events, are characterized using a simple “independent cluster” parametrization in order to quantify their strength (cluster size) and their extent in η (cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb⁻¹ data set at 7 TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate p _T of 1–3 GeV/c, 2.0 < |Δη| < 4.8 and Δϕ ≈ 0. This is the first observation of such a long-range, near-side feature in two-particle correlation functions in pp or \( p\overline p \) collisions.

Jet production in PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV was studied with the Compact Muon Solenoid (CMS) detector at the LHC, using a data sample corresponding to an integrated luminosity of $6.7\mu$b${}^{-1}$. Jets are reconstructed using the energy deposited in the CMS calorimeters and studied as a function of collision centrality. With increasing collision centrality, a striking imbalance in dijet transverse momentum is observed, consistent with jet quenching. The observed effect extends from the lower cutoff used in this study (jet $p_{\mathrm{T}}=120$ GeV/c) up to the statistical limit of the available data sample (jet $p_{\mathrm{T}}\approx 210$ GeV/c). Correlations of charged particle tracks with jets indicate that the momentum imbalance is accompanied by a softening of the fragmentation pattern of the second most energetic, away-side jet. The dijet momentum balance is recovered when integrating low transverse momentum particles distributed over a wide angular range relative to the direction of the away-side jet.

The transverse momentum spectra of charged particles have been measured in pp and PbPb collisions at [equation] by the CMS experiment at the LHC. In the transverse momentum range pT=5–10 GeV/ c, the...

Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$ 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 $d{N}_{\mathrm{ch}}/d\eta {|}_{|\eta |<0.5}=5.78\pm 0.01(\mathrm{stat})\pm 0.23(\mathrm{syst})$ for non-single-diffractive events, higher than predicted by commonly used models. The relative increase in charged-particle multiplicity from $\sqrt{s}=0.9$ to 7 TeV is $[66.1\pm 1.0(\mathrm{stat})\pm 4.2(\mathrm{syst})]\%$. The mean transverse momentum is measured to be $0.545\pm 0.005(\mathrm{stat})\pm 0.015(\mathrm{syst})\mathrm{GeV}/c$. The results are compared with similar measurements at lower energies.

A measurement of inclusive W and Z production cross sections in pp collisions at \( \sqrt {s} = 7 \) 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) × \( \mathcal{B}\left( {{\text{W}} \to \ell \nu } \right) \) = 10.31 ± 0.02 (stat.) ± 0.09 (syst.) ± 0.10 (th.) ± 0.41 (lumi.) nb and σ(pp → ZX) × \( \mathcal{B}\left( {{\text{Z}} \to {\ell^{+} }{\ell^{-} }} \right) \) = 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 → WX) × \( \mathcal{B}\left( {{\text{W}} \to \ell \nu } \right) \)/(σ(pp → ZX) × \( \mathcal{B}\left( {{\text{Z}} \to {\ell^{+} }{\ell^{-} }} \right) \) = 10.54 ± 0.07 (stat.) ± 0.08 (syst.) ± 0.16 (th.) and (σ(pp → W⁺ X) × \( \mathcal{B}\left( {{{\text{W}}^{ + }} \to {\ell^{+} }\nu } \right) \)/(σ(pp → W⁻ X) × \( \mathcal{B}\left( {{{\text{W}}^{-} } \to {\ell^{-} }\bar{\nu }} \right) \) = 1.421 ± 0.006 (stat.) ± 0.014 (syst.) ± 0.029 (th.). The measured values agree with next-to-next-to-leading order QCD cross section calculations based on recent parton distribution functions.