Searches for violation of lepton flavour and baryon number in tau lepton decays at LHCb

Searches for the lepton flavour violating decay $tau^-rightarrow mu^-mu^+mu^-$ and the lepton flavour and baryon number violating decays $tau^-rightarrow bar{p}mu^+mu^-$ and $tau^-rightarrow pmu^-mu^-$ have been carried out using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, taken by the LHCb experiment at $sqrt{s} = 7$ TeV. No evidence has been found for any signal, and limits have been set at 90% confidence level on the branching fractions: $cal B(tau^-rightarrow mu^-mu^+mu^-) < 8.0 times 10^{-8}$, $cal B(tau^-rightarrow bar{p}mu^+mu^-) < 3.3 times 10^{-7}$ and $cal B(tau^-rightarrow pmu^-mu^-) < 4.4 times 10^{-7}$. The results for the $tau^-rightarrow bar{p}mu^+mu^-$ and $tau^-rightarrow pmu^-mu^-$ decay modes represent the first direct experimental limits on these channels.