Top-Quark Mass Measurement from Dilepton Events at CDF II

Abstract

We report a measurement of the top-quark mass using events collected by the CDF II detector from $p\overline{p}$ collisions at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ at the Fermilab Tevatron. We calculate a likelihood function for the top-quark mass in events that are consistent with $t\overline{t}\ensuremath{\rightarrow}\overline{b}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}b{\ensuremath{\ell}}^{\ensuremath{'}+}{\ensuremath{\nu}}_{\ensuremath{\ell}}^{\ensuremath{'}}$ decays. The likelihood is formed as the convolution of the leading-order matrix element and detector resolution functions. The joint likelihood is the product of likelihoods for each of 33 events collected in $340\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ of integrated luminosity, yielding a top-quark mass ${M}_{t}=165.2\ifmmode\pm\else\textpm\fi{}6.1(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}3.4(\mathrm{syst})\text{ }\text{ }\mathrm{GeV}/{c}^{2}$. This first application of a matrix-element technique to $t\overline{t}\ensuremath{\rightarrow}b{\ensuremath{\ell}}^{+}{\ensuremath{\nu}}_{\ensuremath{\ell}}\overline{b}{\ensuremath{\ell}}^{\ensuremath{'}\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{{\ensuremath{\ell}}^{\ensuremath{'}}}$ decays gives the most precise single measurement of ${M}_{t}$ in dilepton events. Combined with other CDF run II measurements using dilepton events, we measure ${M}_{t}=167.9\ifmmode\pm\else\textpm\fi{}5.2(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}3.7(\mathrm{syst})\text{ }\text{ }\mathrm{GeV}/{c}^{2}$.