Measurement of the WZ production cross section in pp collisions at √s=7 and 8 TeV and search for anomalous triple gauge couplings at √s=8TeV

The WZ production cross section is measured by the CMS experiment at the CERN LHC in proton-proton collision data samples corresponding to integrated luminosities of 4.9 inverse femtobarns collected at sqrt(s)= 7 TeV, and 19.6 inverse femtobarns at sqrt(s)= 8 TeV. The measurements are performed using the fully-leptonic WZ decay modes with electrons and muons in the final state. The measured cross sections for 71 < m[Z] < 111 GeV are sigma(pp to WZ; sqrt(s)= 7 TeV) = 20.14 +/- 1.32 (stat) +/- 1.13 (syst) +/- 0.44 (lumi) pb and sigma(pp to WZ; sqrt(s)= 8 TeV) = 24.09 +/- 0.87 (stat) +/- 1.62 (syst) +/- 0.63 (lumi) pb. Differential cross sections with respect to the Z boson pt, the leading jet pt, and the number of jets are obtained using the sqrt(s)= 8 TeV data. The results are consistent with standard model predictions and constraints on anomalous triple gauge couplings are obtained

Performance of the CMS missing transverse momentum reconstruction in pp data at √s = 8 TeV

The performance of missing transverse energy reconstruction algorithms is presented using √s = 8 TeV proton-proton (pp) data collected with the CMS detector. Events with anomalous missing transverse energy are studied, and the performance of algo- rithms used to identify and remove these events is presented. The scale and resolu- tion for missing transverse energy, including the effects of multiple pp interactions (pileup), are measured using events with an identified Z boson or isolated photon, and are found to be well described by the simulation. Novel missing transverse en- ergy reconstruction algorithms developed specifically to mitigate the effects of large numbers of pileup interactions on the missing transverse energy resolution are pre- sented. These algorithms significantly reduce the dependence of the missing trans- verse energy resolution on pileup interactions. Finally, an algorithm that provides an estimate of the significance of the missing transverse energy is presented, which is used to estimate the compatibility of the reconstructed missing transverse energy with a zero nominal value

Search for physics beyond the standard model in final states with a lepton and missing transverse energy in proton-proton collisions at √s = 8 TeV

A search for new physics in proton-proton collisions having final states with an elec- tron or muon and missing transverse energy is presented. The analysis uses data collected in 2012 with the CMS detector, at an LHC center-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of 19.7 fb−1. No significant deviation of the transverse mass distribution of the charged lepton-neutrino system from the standard model prediction is found. Mass exclusion limits of up to 3.28 TeV at 95% confidence level for a W′ boson with the same couplings as that of the standard model W boson are determined. Results are also derived in the framework of split universal extra dimensions, and exclusion limits on Kaluza–Klein W(2) KK states are found. The final state with large missing transverse energy also enables a search for dark matter production with a recoiling W boson, with limits set on the mass and the produc- tion cross section of potential candidates. Finally, limits are established for a model including interference between a left-handed W′ boson and the standard model W boson, and for a compositeness model

Evidence for transverse-momentum- and pseudorapidity-dependent event-plane fluctuations in PbPb and p Pb collisions

A systematic study of the factorization of long-range azimuthal two-particle corre- lations into a product of single-particle anisotropies is presented as a function of pT and η of both particles, and as a function of the particle multiplicity in PbPb and pPb collisions. The data were taken with the CMS detector for PbPb collisions at √sNN = 2.76 TeV and pPb collisions at √sNN = 5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pT and η. When measured with particles of different pT, the magnitude of the factoriza- tion breakdown for the second Fourier harmonic reaches 20% for very central PbPb collisions but decreases rapidly as the multiplicity decreases. The data are consistent with viscous hydrodynamic predictions, which suggest that the effect of factorization breaking is mainly sensitive to the initial-state conditions rather than to the trans- port properties (e.g., shear viscosity) of the medium. The factorization breakdown is also computed with particles of different η. The effect is found to be weakest for mid- central PbPb events but becomes larger for more central or peripheral PbPb collisions, and also for very high-multiplicity pPb collisions. The η-dependent factorization data provide new insights to the longitudinal evolution of the medium formed in heavy ion collisions