Reconstruction and selection of $Z \rightarrow \tau\tau \rightarrow \mu + \tau-jet + \nu's$ decays at the CMS experiment

At the LHC, tau leptons are expected in final states of many important physics processes including Supersymmetry and the production of Higgs boson(s) and other exotic particles. %Within an MSSM scenario they play a central role due to a potential enhancement of the tau coupling. An efficient and accurate $\tau$ reconstruction and identification are therefore an important part of the CMS physics programme. Z$^0$ $\rightarrow \tau^+ \tau^-$ decays are often considered the ``standard candle'' of tau reconstruction as they validate tau lepton identification and provide a test bench for Higgs searches (for which they constitute the main irreducible background). We describe techniques for selecting and reconstructing the Z$^0$ $\rightarrow \tau^\pm \tau^\mp \rightarrow \mu^\pm \nu_\mu \bar{\nu}_\tau$($\bar{\nu}_\mu \nu_\tau$) + $\tau$-jet$^\mp$$\nu_\tau$($\bar{\nu}_\tau$) events that were developed for the measurement of the Z production cross-section by the CMS experiment using 200 pb$^{-1}$ of the LHC collision data at the center-of-mass energy $\sqrt{s}$~=~10~TeV. We validate these techniques using simulated events and present a data-driven method for estimating background contributions to this measurement.