7,401 research outputs found

    Measurement of the W boson mass and width in e+e−e^{+}e^{-} collisions at LEP

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    A review of the present status of the W boson mass and width measurements at LEP is presented. The analysis of the data collected in 1998 by the 4 LEP collaborations, corresponding to about 700 pb /sup -1/, allows to reach an experimental uncertainty on the W boson mass measured at LEPII approaching the precision of the indirect results from the high precision electroweak measurements at LEPI. (7 refs)

    The simulation of the CMS electromagnetic calorimeter

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    The CMS Collaboration has developed a detailed simulation of the electromagnetic calorimeter (ECAL), which has been fully integrated in the collaboration software framework CMSSW. The simulation is based on the Geant4 detector simulation toolkit for the modelling of the passage of particles through matter and magnetic field. The geometrical description of the detector is being re-implemented using the DetectorDescription language, combining an XML based description of with the algorithmic definition of the position of the elements. The ECAL simulation software is fully operational and has been validated using real data from the ECAL test beam experiment that took place in summer 2006

    Electroweak corrections uncertainty on the W mass measurement at LEP

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    The systematic uncertainty on the W mass and width measurement resulting from the imperfect knowledge of electroweak radiative corrections is discussed. The intrinsic uncertainty in the 4-f generator used by the DELPHI Collaboration is studied following the guidelines of the authors of YFSWW, on which its radiative corrections part is based. The full DELPHI simulation, reconstruction and analysis chain is used for the uncertainty assessment. A comparison with the other available 4-f calculation implementing DPA O(alpha) corrections, RacoonWW, is also presented. The uncertainty on the W mass is found to be below 10 MeV for all the WW decay channels used in the measurement.Comment: 34 pages, 3 figure

    Event reweighting to account for DPA

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    Radiative Corrections on CC03

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    Measurements of the associated production of a W boson and a charm quark in proton-proton collisions at sqrt(s) = 8 TeV

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    Measurements of the associated production of a W boson and a charm (c) quark in proton–proton collisions at a centre-of-mass energy of 8TeV are reported. The analysis uses a data sample corresponding to a total integrated luminosity of 19.7fb−1 collected by the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm quark jets are selected using distinctive signatures of charm hadron decays. The product of the cross section and branching fraction σ(pp→W+c+X)B(W→ℓΜ), where ℓ=e or ÎŒ, and the cross section ratio σ(pp→W++cÂŻ+X)/σ(pp→W−+c+X) are measured in a fiducial volume and differentially as functions of the pseudorapidity and of the transverse momentum of the lepton from the W boson decay. The results are compared with theoretical predictions. The impact of these measurements on the determination of the strange quark distribution is assessed

    Measurements of production cross sections of polarized same-sign W boson pairs in association with two jets in proton-proton collisions at sqrt(s) = 13 TeV

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    The first measurements of production cross sections of polarized same-sign W±W± boson pairs in proton-proton collisions are reported. The measurements are based on a data sample collected with the CMS detector at the LHC at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 137fb−1. Events are selected by requiring exactly two same-sign leptons, electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass to enhance the contribution of same-sign W±W± scattering events. An observed (expected) 95% confidence level upper limit of 1.17 (0.88) fbis set on the production cross section for longitudinally polarized same-sign W±W± boson pairs. The electroweak production of same-sign W±W± boson pairs with at least one of the W bosons longitudinally polarized is measured with an observed (expected) significance of 2.3 (3.1) standard deviations

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

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    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

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

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    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
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