Searches for Violation of Lepton Flavour and Baryon Number in Tau Lepton Decays at LHCb

Searches for the lepton flavour violating decay τ− → μ− μ+ μ− and the lepton flavour and baryon number violating decays τ− → anti-p μ+ μ− and τ− → p μ− μ− 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 √s = 7 TeV. No evidence has been found for any signal, and limits have been set at 90% confidence level on the branching fractions: B(τ− → μ− μ+ μ−) < 8.0 x 10^−8, B(τ− → anti-p μ+ μ−) < 3.3 x 10^−7 and B(τ− → p μ− μ−) < 4.4 x 10^−7. The results for the τ− → anti-p μ+ μ− and τ− → p μ− μ− decay modes represent the first direct experimental limits on these channels.