[Show abstract][Hide abstract] ABSTRACT: Measurements of the [Formula: see text][Formula: see text] production cross sections in proton-proton collisions at center-of-mass energies of 7 and 8[Formula: see text] are presented. Candidate events for the leptonic decay mode [Formula: see text], where [Formula: see text] denotes an electron or a muon, are reconstructed and selected from data corresponding to an integrated luminosity of 5.1 (19.6)[Formula: see text] at 7 (8)[Formula: see text] collected with the CMS experiment. The measured cross sections, [Formula: see text] at 7[Formula: see text], and [Formula: see text] at 8[Formula: see text], are in good agreement with the standard model predictions with next-to-leading-order accuracy. The selected data are analyzed to search for anomalous triple gauge couplings involving the [Formula: see text][Formula: see text] final state. In the absence of any deviation from the standard model predictions, limits are set on the relevant parameters. These limits are then combined with the previously published CMS results for [Formula: see text][Formula: see text] in 4[Formula: see text] final states, yielding the most stringent constraints on the anomalous couplings.
European Physical Journal C 11/2015; 75(10):511. DOI:10.1140/epjc/s10052-015-3706-0 · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper describes the algorithms used by the CMS experiment to reconstruct and identify tau to hadrons + tau decays during Run 1 of the LHC. The performance of the algorithms is studied in proton-proton collisions recorded at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 inverse femtobarns. The algorithms achieve an identification efficiency of 50-60%, with misidentification rates for quark and gluon jets, electrons, and muons between per mille and per cent levels.
[Show abstract][Hide abstract] ABSTRACT: A search for a heavy Higgs boson in the H → WW and H → ZZ decay channels is reported. The search is based upon proton-proton collision data samples corresponding to an integrated luminosity of up to 5.1 fb−1 at √ s = 7 TeV and up to 19.7fb−1 at √ s = 8 TeV, recorded by the CMS experiment at the CERN LHC. Several final states of the H → WW and H → ZZ decays are analyzed. The combined upper limit at the 95% confidence level on the product of the cross section and branching fraction exclude a Higgs boson with standard model-like couplings and decays in the range 145 < mH < 1000 GeV. We also interpret the results in the context of an electroweak singlet extension of the standard model.[Figure not available: see fulltext.]
Journal of High Energy Physics 10/2015; 2015(10). DOI:10.1007/JHEP10(2015)144 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A comparison of the differential cross sections for the processes Z/γ* + jets and photon (γ)+jets is presented. The measurements are based on data collected with the CMS detector at s=8(Formula presented.) TeV corresponding to an integrated luminosity of 19.7 fb−1. The differential cross sections and their ratios are presented as functions of pT. The measurements are also shown as functions of the jet multiplicity. Differential cross sections are obtained as functions of the ratio of the Z/γ*pT to the sum of all jet transverse momenta and of the ratio of the Z/γ*pT to the leading jet transverse momentum. The data are corrected for detector effects and are compared to simulations based on several QCD calculations.[Figure not available: see fulltext.]
Journal of High Energy Physics 10/2015; 2015(10). DOI:10.1007/JHEP10(2015)128 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A systematic study of the factorization of long-range azimuthal two-particle correlations 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 factorization 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 transport 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.
Physical Review C 09/2015; 92(3). DOI:10.1103/PhysRevC.92.034911 · 3.73 Impact Factor