Measurement of the Top Quark Mass Using Dilepton Events

The D0 Collaboration has performed a measurement of the top quark mass ${m}_{t}$ based on six candidate events for the process $t\overline{t}\ensuremath{\rightarrow}{\mathrm{bW}}^{+}\overline{b}{W}^{\ensuremath{-}}$, where the $W$ bosons decay to $e\ensuremath{\nu}$ or $\ensuremath{\mu}\ensuremath{\nu}$. This sample was collected during an exposure of the D0 detector to an integrated luminosity of $125{\mathrm{pb}}^{\ensuremath{-}1}$ of $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\phantom{\rule{0ex}{0ex}}\mathrm{TeV}p\overline{p}$ collisions. We obtain ${m}_{t}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}168.4\ifmmode\pm\else\textpm\fi{}12.3(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}3.6(\mathrm{syst})\phantom{\rule{0ex}{0ex}}\mathrm{GeV}{/c}^{2}$, consistent with the measurement obtained using single-lepton events. Combination of the single-lepton and dilepton results yields ${m}_{t}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}172.0\ifmmode\pm\else\textpm\fi{}7.5\mathrm{GeV}{/c}^{2}$.