We give a detailed description of the measurement of the W boson mass, MW , performed on an integrated luminosity of 4.3 fb −1 , which is based on similar techniques as used for our previous measurement done on an independent data set of 1 fb −1 of data. The data were collected using the D0 detector at the Fermilab Tevatron Collider. This data set yields 1.68 × 10 6 W → eν candidate events. We measure the mass using the transverse mass, electron transverse momentum, and missing transverse energy distributions. The MW measurements using the transverse mass and the electron transverse momentum distributions are the most precise of these three and are combined to give MW = 80.367 ± 0.013 (stat) ± 0.022 (syst) GeV = 80.367 ± 0.026 GeV. When combined with our earlier measurement on 1 fb −1 of data, we obtain MW = 80.375 ± 0.023 GeV.

We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of 5.4 fb −1 , collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the tt forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.

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We determine the top quark mass m t using t t pairs produced in the DO " detector by ͱsϭ1.8 TeV pp collisions in a 125 pb Ϫ1 exposure at the Fermilab Tevatron. We make a two constraint fit to m t in t t→bW ϩ b W Ϫ final states with one W boson decaying to qq and the other to e or . Likelihood fits to the data yield m t (lϩjets)ϭ173.3Ϯ5.6 (stat) Ϯ 5.5 (syst) GeV/c 2 . When this result is combined with an analysis of events in which both W bosons decay into leptons, we obtain m t ϭ172.1Ϯ5.2 (stat) Ϯ 4.9 (syst) GeV/c 2 . An alternate analysis, using three constraint fits to fixed top quark masses, gives m t (lϩjets)ϭ176.0 Ϯ7.9 (stat)Ϯ 4.8 (syst) GeV/c 2 , consistent with the above result. Studies of kinematic distributions of the top quark candidates are also presented. ͓S0556-2821͑98͒06815-5͔

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