  We present a measurement of the W boson mass in proton-antiproton collisions
at \sqrt{s} = 1.8 TeV based on a data sample of 82 pb^-1 integrated luminosity
collected by the D0 detector at the Fermilab Tevatron. We utilize e \nu events
in which the electron shower is close to the phi edge of one of the 32 modules
in the D0 central calorimeter. The electromagnetic calorimenter response and
resolution in this region differs from that in the rest of the module and
electrons in this region were not previously utilized. We determine the
calorimeter response and resolution in this region using Z -> ee events. We
extract the W boson mass by fitting to the transverse mass and to the electron
and neutrino transverse momentum distributions. The result is combined with
previous D0 results to obtain an improved measurement of the W boson mass: m_W
= 80.483 +- 0.084 GeV.
