ATLAS soft tau reconstruction performance in the mSUGRA stau coannihilation region

We study the performance of the tau reconstruction algorithms tauRec and tau1P3P on simulated ATLAS data. We focus primarily on soft taus, an important signature of several models of new physics observable at the LHC. Optimisation of soft tau reconstruction is investigated, and the obtained performance is compared for the two algorithms. Some observations concerning tau decay kinematics in the generators Herwig and Pythia are documented. We use both algorithms to reconstruct the invariant mass of the tau pairs from the cascade ecay $\chi_2^0 \rightarrow \tilde{\tau}+\tau ; \tilde{\tau}\rightarrow\tau+\chi_1^0$ in the mSUGRA stau coannihilation region. The results are compared with generator level information and with analytical end-point calculations. We find that the kinematical endpoint of the $m_{\tau^{+} \tau^{-}}$ distribution can be reconstructed with 16 pb$^{-1}$ of data, using a linear fit and tau1P tau reconstruction. A sample of $Z \rightarrow \tau \tau $ is used as a reference for the performance studies.