Measurement of $\sigma (p\overline{p}\to Z)·\mathrm{Br}(Z\to \tau \tau )$ at $\sqrt{s}=1.96\mathrm{TeV}$

We present a measurement of the cross section for $Z$ production times the branching fraction to $\tau$ leptons, $\sigma ·\mathrm{Br}(Z\to {\tau }^{+}{\tau }^{-})$, in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ in the channel in which one $\tau$ decays into $\mu {\nu }_{\mu }{\nu }_{\tau }$, and the other into $\mathrm{hadrons}+{\nu }_{\tau }$ or $e{\nu }_e{\nu }_{\tau }$. The data sample corresponds to an integrated luminosity of $226{\mathrm{pb}}^{-1}$ collected with the D0 detector at the Fermilab Tevatron collider. The final sample contains 2008 candidate events with an estimated background of 55%. From this we obtain $\sigma ·\mathrm{Br}(Z\to {\tau }^{+}{\tau }^{-})=237\pm 15(\mathrm{\text{stat}})\pm 18(\mathrm{\text{sys}})\pm 15(\mathrm{\text{lum}})\mathrm{pb}$, in agreement with the standard model prediction.