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

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

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

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

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

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→ℓν), where ℓ=e or μ, and the cross section ratio σ(pp→W++c¯+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

Azimuthal correlations within exclusive dijets with large momentum transfer in photon-lead collisions

The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at √sNN=5.02 TeV, corresponding to an integrated luminosity of 0.38 nb−1, collected with the CMS experiment at the LHC. The measured second harmonic of the correlation between the sum and difference of the two jet transverse momentum vectors is found to be positive, and rising, as the dijet transverse momentum increases. A well-tuned model that has been successful at describing a wide range of proton scattering data from the HERA experiments fails to describe the observed correlations, suggesting the presence of gluon polarization effects

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

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

Measurement of differential cross sections for the production of a Z boson in association with jets in proton-proton collisions at sqrt(s) = 13 TeV

measurement is presented of the production of Z bosons that decay into two electrons or muons in association with jets, in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were recorded by the CMS Collaboration at the LHC with an integrated luminosity of 35.9 fb −1 . The differential cross sections are measured as a function of the transverse momentum (p T ) of the Z boson and the transverse momentum and rapidities of the five jets with largest pT . The jet multiplicity distribution is measured for up to eight jets. The hadronic activity in the events is estimated using the scalar sum of the p T of all the jets. All measurements are unfolded to the stable-particle level and compared with predictions from various Monte Carlo event generators, as well as with expectations at leading and next-to-leading orders in perturbative quantum chromodynamics