Observation of the diphoton decay of the Higgs boson and measurement of its properties

Peer reviewe

Study of Vector Boson Scattering and Search for New Physics in Events with Two Same-Sign Leptons and Two Jets

A study of vector boson scattering in pp collisions at a center-of-mass energy of 8 TeV is presented. The data sample corresponds to an integrated luminosity of 19.4 fb(-1) collected with the CMS detector. Candidate events are selected with exactly two leptons of the same charge, two jets with large rapidity separation and high dijet mass, and moderate missing transverse energy. The signal region is expected to be dominated by electroweak same-sign W-boson pair production. The observation agrees with the standard model prediction. The observed significance is 2.0 standard deviations, where a significance of 3.1 standard deviations is expected based on the standard model. Cross section measurements for (WW +/-)-W-+/- and WZ processes in the fiducial region are reported. Bounds on the structure of quartic vector-boson interactions are given in the framework of dimension-eight effective field theory operators, as well as limits on the production of doubly charged Higgs bosons

Search for heavy neutrinos and W bosons with right-handed couplings in proton-proton collisions at sqrt(s) = 8 TeV

Submitted to Eur. Phys. J. C. arXiv admin note: text overlap with arXiv:1405.7225 ; see paper for full list of authorsA search for heavy, right-handed neutrinos, N[l] (l = e, mu), and right-handed WR bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS experiment. The search was based on a sample of two lepton plus two jet events collected in proton-proton collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 inverse femtobarns. No significant excess of events over the standard model expectation is observed. For models with strict left-right symmetry, and assuming only one N[l] flavor contributes significantly to the WR decay width, the region in the two-dimensional (M[WR], M[N]) mass plane excluded at a 95% confidence level extends to approximately M[WR] = 3.0 TeV and covers a large range of neutrino masses below the WR boson mass, depending on the value of M[WR]. This search significantly extends the (M[WR], M[N]) exclusion region beyond previous results

Measurement of the ratio B(t›Wb)/B(t›Wq) in pp collisions at s=8 TeV

The ratio of the top-quark branching fractions R=B(t›Wb)/B(t›Wq), where the denominator includes the sum over all down-type quarks (q=b,s,d), is measured in the tt¯ dilepton final state with proton–proton collision data at s=8 TeV from an integrated luminosity of 19.7 fb-1, collected with the CMS detector. In order to quantify the purity of the signal sample, the cross section is measured by fitting the observed jet multiplicity, thereby constraining the signal and background contributions. By counting the number of b jets per event, an unconstrained value of R=1.014±0.003(stat.)±0.032(syst.) is measured, in a good agreement with current precision measurements in electroweak and flavour sectors. A lower limit R>0.955 at the 95% confidence level is obtained after requiring R?1, and a lower limit on the Cabibbo–Kobayashi–Maskawa matrix element |Vtb|>0.975 is set at 95% confidence level. The result is combined with a previous CMS measurement of the t-channel single-top-quark cross section to determine the top-quark total decay width, ?t=1.36±0.02(stat.)-0.11 +0.14(syst.) GeV. © 2014 The Author