We present the first direct measurement of the top-quark mass using $t\overline{t}$ events decaying in the hadronic $\tau +\mathrm{\text{jets}}$ decay channel. Using data corresponding to an integrated luminosity of $2.2{\mathrm{fb}}^{-1}$ collected by the CDF II detector in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ at the Fermilab Tevatron, we measure the $t\overline{t}$ cross section, ${\sigma }_{t\overline{t}}$, and the top-quark mass, $M_{\mathrm{top}}$. We extract $M_{\mathrm{top}}$ from a likelihood based on per-event probabilities calculated with leading-order signal and background matrix elements. We measure ${\sigma }_{t\overline{t}}=8.8\pm 3.3(\mathrm{stat})\pm 2.2(\mathrm{syst})\mathrm{pb}$ and $M_{\mathrm{top}}=172.7\pm 9.3(\mathrm{stat})\pm 3.7(\mathrm{syst})\mathrm{GeV}/c^2$.

• Received 29 August 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.192001