Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.Comment: Submitted to Physics Letters

Measurement of the mass difference between top quark and antiquark in pp collisions at root s=8 TeV

Peer reviewe

Measurement of the production cross section for a W boson and two b jets in pp collisions at root s=7 TeV

The production cross section for a W boson and two b jets is measured using proton&#8211;proton collisions at s=7 TeV in a data sample collected with the CMS experiment at the LHC corresponding to an integrated luminosity of 5.0 fb &#8722;1 . The W+bb¯ events are selected in the W&#8594;&#956;&#957; decay mode by requiring a muon with transverse momentum pT>25 GeV and pseudorapidity |&#951;|25 GeV and |&#951;|<2.4 . The measured W+bb¯ production cross section in the fiducial region, calculated at the level of final-state particles, is &#963;(pp&#8594;W+bb¯)×B(W&#8594;&#956;&#957;)=0.53±0.05(stat.)±0.09(syst.)±0.06(theo.)±0.01(lum.) pb , in agreement with the standard model prediction. In addition, kinematic distributions of the W+bb¯ system are in agreement with the predictions of a simulation using MadGraph and pythia

Measurements of the t(t)Overbar charge asymmetry using the dilepton decay channel in pp collisions at root s=7 TeV

The tt¯ charge asymmetry in proton-proton collisions at s&#8730; = 7 TeV is measured using the dilepton decay channel (ee, e &#956; , or &#956;&#956; ). The data correspond to a total integrated luminosity of 5.0 fb &#8722;1 , collected by the CMS experiment at the LHC. The tt and lepton charge asymmetries, defined as the differences in absolute values of the rapidities between the reconstructed top quarks and antiquarks and of the pseudorapidities between the positive and negative leptons, respectively, are measured to be A C = &#8722;0 . 010 ± 0 . 017 (stat . ) ± 0 . 008 (syst . ) and AlepC = 0 . 009 ± 0 . 010 (stat . ) ± 0 . 006 (syst . ). The lepton charge asymmetry is also measured as a function of the invariant mass, rapidity, and transverse momentum of the tt¯ system. All measurements are consistent with the expectations of the standard model

Measurement of the t-channel single-top-quark production cross section and of the |Vtb| CKM matrix element in pp collisions at SQR = 8 TeV

Measurements are presented of the t -channel single-top-quark production cross section in proton-proton collisions at s&#8730; = 8 TeV. The results are based on a data sample corresponding to an integrated luminosity of 19.7 fb &#8722;1 recorded with the CMS detector at the LHC. The cross section is measured inclusively, as well as separately for top (t) and antitop (t¯) , in final states with a muon or an electron. The measured inclusive t -channel cross section is &#963; t -ch. = 83 . 6 ± 2 . 3 (stat.) ± 7 . 4 (syst.) pb. The single t and t¯ cross sections are measured to be &#963; t -ch. ( t ) = 53 . 8 ± 1 . 5 (stat.) ± 4 . 4 (syst.) pb and &#963; t -ch. (t¯) = 27 . 6 ± 1 . 3 (stat.) ± 3 . 7 (syst.) pb, respectively. The measured ratio of cross sections is R t -ch. = &#963; t -ch. (t) /&#963; t -ch. (t¯) = 1 . 95 ± 0 . 10 (stat.) ± 0 . 19 (syst.), in agreement with the standard model prediction. The modulus of the Cabibbo-Kobayashi-Maskawa matrix element V tb is extracted and, in combination with a previous CMS result at s&#8730; = 7 TeV, a value | V tb | = 0 . 998 ± 0 . 038 (exp.) ± 0 . 016 (theo.) is obtained