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 \(\tau^-\rightarrow p\mu^-\mu^-\) 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 \(\cal B(\tau^-\rightarrow p\mu^-\mu^-) < 4.4 \times 10^{-7}\). The results for the \(\tau^-\rightarrow \bar{p}\mu^+\mu^-\) and \(\tau^-\rightarrow p\mu^-\mu^-\) decay modes represent the first direct experimental limits on these channels.