Constraints on anomalous Higgs boson couplings using production and decay information in the four-lepton final state

A search is performed for anomalous interactions of the recently discovered Higgs boson using matrix element techniques with the information from its decay to four leptons and from associated Higgs boson production with two quark jets in either vector boson fusion or associated production with a vector boson. The data were recorded by the CMS experiment at the LHC at a center-of-mass energy of and correspond to an integrated luminosity of . They are combined with the data collected at center-of-mass energies of 7 and , corresponding to integrated luminosities of 5.1 and , respectively. All observations are consistent with the expectations for the standard model Higgs boson

Associated production of heavy flavors and W, Z bosons at CMS

The mechanism of production of heavy-flavoured jets, originated by the hadronization of b or c quarks, in association with vector bosons, W or Z, in the Standard Model is of primary importance. It allows to refine the theoretical calculations in perturbative QCD, as well as validate associated predictions from simulation. The understanding of these processes is furthermore required by Higgs and Beyond the Standard Model searches with similar final states. Using the LHC proton-proton collision data collected at a center-of-mass energy of 7TeV by the CMS detector, measurements of the W+b, W+c, Z+b and Z+B hadrons cross sections are presented, comparing experimental data with several theoretical predictions in quantum chromodynamics

Performance of a Tungsten-Cerium Fluoride Sampling Calorimeter in High-Energy Electron Beam Tests

A prototype for a sampling calorimeter made out of cerium fluoride crystals interleaved with tungsten plates, and read out by wavelength-shifting fibres, has been exposed to beams of electrons with energies between 20 and 150 GeV, produced by the CERN Super Proton Synchrotron accelerator complex. The performance of the prototype is presented and compared to that of a Geant4 simulation of the apparatus. Particular emphasis is given to the response uniformity across the channel front face, and to the prototype's energy resolution.Comment: 6 pages, 6 figures, Submitted to NIM

W and Z studies at CMS

Selected measurements done with W and Z bosons detected in the CMS detector, based on samples of events collected during 2011 at 7TeV and 2012 at 8TeV physics runs, are presented. Results on the inclusiveWand Z cross sections and the lepton charge asymmetry in the reconstructedWevents decaying to a lepton and a neutrino, obtained in the electron and muon decay channels, are presented. Differential cross section, forward-backward asymmetry and electroweak couplings of events coming from the Drell-Yan process are compared with the corresponding theoretical QCD prediction comparison

Observation of top quark pairs produced in association with a vector boson in pp collisions at sqrt(s) = 8 TeV

Measurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8TeV pp collision data corresponding to an integrated luminosity of 19.5 fb1, collected by the CMS experiment at the LHC. Final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identied by matching reconstructed objects in the detector to specic nal state particles from ttW or ttZ decays. The ttW cross section is measured to be 382+117 102 fb with a signicance of 4.8 standard deviations from the background-only hypothesis. The ttZ cross section is measured to be 242+65 55 fb with a signicance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on ve anomalous dimension-six operators that would aect the ttW and ttZ cross sections

Search for dijet resonances in proton-proton collisions at sqrt(s) = 13 TeV and constraints on dark matter and other models

A search is presented for narrow resonances decaying to dijet final states in proton-proton collisions at root s = 13 TeV using data corresponding to an integrated luminosity of 12.9 fb(-1). The dijet mass spectrum is well described by a smooth parameterization and no significant evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 0.6TeV. In the context of specific models, the limits exclude string resonances with masses below 7.4TeV, scalar diquarks below 6.9TeV, axigluons and colorons below 5.5TeV, excited quarks below 5.4TeV, color-octet scalars below 3.OTeV, W' bosons below 2.7 TeV, Z' bosons below 2.1 TeV and between 2.3 and 2.6 TeV, and RS gravitons below 1.9 TeV. These extend previous limits in the dijet channel. Vector and axial-vector mediators in a simplified model of interactions between quarks and dark matter are excluded below 2.0 TeV. The first limits in the dijet channel on dark matter mediators are presented as functions of dark matter mass and are compared to the exclusions of dark matter in direct detection experiments. (C) 2017 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license

Search for standard model production of four top quarks in the lepton + jets channel in pp collisions at sqrt(s) = 8 TeV

A search is presented for standard model (SM) production of four top quarks (tt\uaftt\uaf) in pp collisions in the lepton + jets channel. The data correspond to an integrated luminosity of 19.6 fb 121 recorded at a centre-of-mass energy of 8 TeV with the CMS detector at the CERN LHC. The expected cross section for SM tt\uaftt\uaf production is \u3c3SMtt\uaftt\uaf 481fb. A combination of kinematic reconstruction and multivariate techniques is used to distinguish between the small signal and large background. The data are consistent with expectations of the SM, and an upper limit of 32 fb is set at a 95% confidence level on the cross section for producing four top quarks in the SM, where a limit of 32 \ub1 17 fb is expected

Measurement of the W+W- cross section in pp collisions at sqrt(s) = 8 TeV and limits on anomalous gauge couplings

A measurement of the W boson pair production cross section in proton-proton collisions at $\sqrt{s} = 8$ TeV is presented. The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 19.4$\,\text {fb}^\text {-1}$. The ${{\mathrm{W} }^{+} }\mathrm{W}^{-}$ candidates are selected from events with two charged leptons, electrons or muons, and large missing transverse energy. The measured ${{\mathrm{W} }^{+} }\mathrm{W}^{-}$ cross section is $60.1\pm 0.9\,\text {(stat)} \pm 3.2\,\text {(exp)} \pm 3.1\,\text {(theo)} \pm 1.6\,\text {(lumi)} \text {\,pb} = 60.1\pm 4.8\text {\,pb}$, consistent with the standard model prediction. The ${{\mathrm{W} }^{+} }\mathrm{W}^{-}$ cross sections are also measured in two different fiducial phase space regions. The normalized differential cross section is measured as a function of kinematic variables of the final-state charged leptons and compared with several perturbative QCD predictions. Limits on anomalous gauge couplings associated with dimension-six operators are also given in the framework of an effective field theory. The corresponding 95 % confidence level intervals are $-5.7< c_{\mathrm {WWW}}/\Lambda ^2 < 5.9\,\mathrm{TeV}^{-2}$, $-11.4< c_{\mathrm {W}}/\Lambda ^2 < 5.4\,\mathrm{TeV}^{-2}$, $-29.2< c_{\mathrm {B}}/\Lambda ^2 < 23.9\,\mathrm{TeV}^{-2}$, in the HISZ basis

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

Measurements are presented of the t-channel single-top-quark production cross section in proton-proton collisions at s 1a = 8 TeV. The results are based on a data sample corresponding to an integrated luminosity of 19.7 fb 121 recorded with the CMS detector at the LHC. The cross section is measured inclusively, as well as separately for top (t) and antitop (t\uaf), in final states with a muon or an electron. The measured inclusive t-channel cross section is \u3c3t-ch. = 83.6 \ub1 2.3 (stat.) \ub1 7.4 (syst.) pb. The single t and t\uaf cross sections are measured to be \u3c3t-ch.(t) = 53.8 \ub1 1.5 (stat.) \ub1 4.4 (syst.) pb and \u3c3t-ch.(t\uaf) = 27.6 \ub1 1.3 (stat.) \ub1 3.7 (syst.) pb, respectively. The measured ratio of cross sections is Rt-ch. = \u3c3t-ch.(t)/\u3c3t-ch.(t\uaf) = 1.95 \ub1 0.10 (stat.) \ub1 0.19 (syst.), in agreement with the standard model prediction. The modulus of the Cabibbo-Kobayashi-Maskawa matrix element Vtb is extracted and, in combination with a previous CMS result at s 1a = 7 TeV, a value |Vtb| = 0.998 \ub1 0.038 (exp.) \ub1 0.016 (theo.) is obtained

Search for the associated production of the Higgs boson with a top-quark pair

A search for the standard model Higgs boson produced in association with a top-quark pair (tt\uafH) is presented, using data samples corresponding to integrated luminosities of up to 5.1 fb 121 and 19.7 fb 121 collected in pp collisions at center-of-mass energies of 7 TeV and 8 TeV respectively. The search is based on the following signatures of the Higgs boson decay: H \u2192 hadrons, H \u2192 photons, and H \u2192 leptons. The results are characterized by an observed tt\uafH signal strength relative to the standard model cross section, \u3bc=\u3c3/\u3c3 SM,under the assumption that the Higgs boson decays as expected in the standard model. The best fit value is \u3bc = 2.8 \ub1 1.0 for a Higgs boson mass of 125.6 GeV