Measurement of theWboson mass using large rapidity electrons

We present a measurement of the W boson mass using data collected by the DØ experiment at the Fermilab Tevatron during 1994–1995. We identify W bosons by their decays to $e\nu$ final states where the electron is detected in a forward calorimeter. We extract the W boson mass $M_W$ by fitting the transverse mass and transverse electron and neutrino momentum spectra from a sample of 11 089 $\overrightarrow{W}e\nu$ decay candidates. We use a sample of 1687 dielectron events, mostly due to $\overrightarrow{Z}\mathrm{ee}$ decays, to constrain our model of the detector response. Using the forward calorimeter data, we measure $M_W=80.691\mathrm{}\pm 0.227\hspace{0.5em}\mathrm{GeV}.$ Combining the forward calorimeter measurements with our previously published central calorimeter results, we obtain $M_W=80.482\mathrm{}\pm 0.091\hspace{0.5em}\mathrm{GeV}.$