Measurement of $\sigma(Z(\rightarrow\tau\tau)+b)/\sigma(Z(\rightarrow\mu\mu)+b)$ ratio

We measure the ratio of cross sections $Z(\rightarrow\tau\tau)+b$ to $Z(\rightarrow\mu\mu)+b$ in $p\bar{p}$ collision at $\sqrt{s}=1.96$ TeV using the D\Odetector. The measurement was performed using a data sample in which one of the taus decays hadronically and the other one to muon. Opposite sign events are used to estimate the backgrounds. The data sample corresponds to an integrated luminosity of 226 $pb^-1$ collected at D\O\ between September 2002 and April 2004.