Measurement of the W boson mass using electrons at large rapidities

We report a measurement of the W boson mass based on an integrated luminosity of 82 pb(-1) from p&pmacr; collisions at sqrt[s] = 1.8 TeV recorded in 1994-1995 by the D0 detector at the Fermilab Tevatron. We identify W bosons by their decays to enu, where the electron is detected in the forward calorimeters. We extract the mass by fitting the transverse mass and the electron and neutrino transverse momentum spectra of 11 089 W boson candidates. We measure M(W) = 80.691+/-0.227 GeV. By combining this measurement with our previously published central calorimeter results from data taken in 1992-1993 and 1994-1995, we obtain M(W) = 80.482+/-0.091 GeV.