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.

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We report a measurement of the mass of the top quark in lepton+jets final states of pp →tt data corresponding to 2.6 fb −1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. A matrix-element method is developed that combines an in situ jet energy calibration with our standard jet energy scale derived from studies of γ+jet and dijet events. We then implement a flavor-dependent jet response correction through a novel approach. This method is used to measure a top-quark mass of mt = 176.01 ± 1.64 GeV. Combining this result with our previous result obtained on an independent data set, we measure a top-quark mass of mt = 174.94 ± 1.49 GeV for a total integrated luminosity of 3.6 fb −1 .

We describe the design, construction and performance of the upgraded DØ muon system for Run II of the Fermilab Tevatron collider. Significant improvements have been made to the major subsystems of the DØ muon detector: trigger scintillation counters, tracking detectors, and electronics. The Run II central muon detector has a new scintillation counter system inside the iron toroid and an improved scintillation counter system outside the iron toroid. In the forward region, new scintillation counter and tracking systems have been installed. Extensive shielding has been added in the forward region. A large fraction of the muon system electronics is also new.

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