Study of CMS sensitivity to neutrinoless τ decay at LHC

The Large Hadron Collider (LHC), scheduled to start operation in 2006, is foreseen to provide in the first year of running a total of similar to 10(12) tau leptons. CMS (Compact Muon Solenoid) is a general-purpose experiment designed to study proton-proton and heavy-ion collisions at LHC. Even if the Susy particles and Higgs searches together with the B-physics provide its main goal, the large number of tau-leptons provided, could allow a systematic study of tau-physics. We have performed a full simulation of CMS using GEANT 3 package and the object-oriented reconstruction program ORCA to study the sensitivity to neutrinoless tau decay tau --> mu(+)mu(-)mu(-) and tau --> mugamma. We present the analysis developed for these channels and the results obtained.