Phys. Rev. D

We present a measurement of the muon charge asymmetry from the decay of the W boson via W→μν using 7.3  fb-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider at s=1.96  TeV. The muon charge asymmetry is presented in two kinematic regions in muon transverse momentum and event missing transverse energy: (pTμ>25  GeV, E̸T>25  GeV) and (pTμ>35  GeV, E̸T>35  GeV). The measured asymmetries are compared with theory predictions made using three parton distribution function sets. The data at pTμ>35  GeV, E̸T>35  GeV, and larger values of |ημ| favor an increased d(x)/u(x) ratio at higher values of x than is predicted.

Phys. Rev. D

We present a comprehensive analysis of inclusive W(→eν)+n-jet (n≥1, 2, 3, 4) production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Tevatron collider using a 3.7  fb-1 data set collected by the D0 detector. Differential cross sections are presented as a function of the jet rapidities (y), lepton transverse momentum (pT) and pseudorapidity (η), the scalar sum of the transverse energies of the W boson and all jets (HT), leading dijet pT and invariant mass, dijet rapidity separations for a variety of jet pairings for pT-ordered and angular-ordered jets, dijet opening angle, dijet azimuthal angular separations for pT-ordered and angular-ordered jets, and W boson transverse momentum. The mean number of jets in an event containing a W boson is measured as a function of HT, and as a function of the rapidity separations between the two highest-pT jets and between the most widely separated jets in rapidity. Finally, the probability for third-jet emission in events containing a W boson and at least two jets is studied by measuring the fraction of events in the inclusive W+2-jet sample that contain a third jet over a pT threshold. The analysis employs a regularized singular value decomposition technique to accurately correct for detector effects and for the presence of backgrounds. The corrected data are compared to particle level next-to-leading-order perturbative QCD predictions, predictions from all-order resummation approaches, and a variety of leading-order and matrix element plus parton shower event generators. Regions of the phase space where there is agreement or disagreement with the data are discussed for the different models tested.

Eur.Phys.J.C

Isolated lepton momenta, in particular their directions are the most precisely measured quantities in pp collisions at LHC. This offers opportunities for multitude of precision measurements. It is of practical importance to verify if precision measurements with lep- tons in the final state require all theoretical effects evaluated simultaneously or if QED bremsstrahlung in the final state can be separated without unwanted precision loss. Results for final state bremsstrahlung in the decays of narrow resonances are obtained from the Feynman rules of QED in an unambiguous way and can be controlled with a very high precision. Also for resonances of non-negligible width, if calculations are appropriately performed, such separation from the remaining electroweak effects can be expected. Our paper is devoted to validation that final state QED bremsstrahlung can indeed be separated from the rest of QCD and electroweak effects, in the production and decay of Z and W bosons, and to estimation of the resulting systematic error. The quantitative discussion is based on Monte Carlo programs PHOTOS and SANC, as well as on KKMC which is used for benchmark results. We show, that for a large classes of W and Z boson observables as used at LHC, theoretical error on photonic bremsstrahlung is 0.1 or 0.2%, depending on the program options used. An overall theoretical error on QED final state radiation, i.e. taking into account missing corrections due to pair emission and interference with initial state radiation is estimated respectively at 0.2% or 0.3% again depending on the program option used.