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

Abstract

Searches for the lepton flavour violating decay $\ddot{I}{„}^{-}\to \hat{I}{¼}^{-}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ and the lepton flavour and baryon number violating decays $\ddot{I}{„}^{-}\to \bar{p}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ and $\ddot{I}{„}^{-}\to p\hat{I}{¼}^{-}\hat{I}{¼}^{-}$ 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: $\mathcal{B}(\ddot{\mathcal{I}}{„}^{-}\to \hat{\mathcal{I}}{¼}^{-}\hat{\mathcal{I}}{¼}^{+}\hat{\mathcal{I}}{¼}^{-})<8.0\times 10^{-8}$, $\mathcal{B}(\ddot{\mathcal{I}}{„}^{-}\to \bar{p}\hat{\mathcal{I}}{¼}^{+}\hat{\mathcal{I}}{¼}^{-})<3.3\times 10^{-7}$ and $\mathcal{B}(\ddot{\mathcal{I}}{„}^{-}\to p\hat{\mathcal{I}}{¼}^{-}\hat{\mathcal{I}}{¼}^{-})<4.4\times 10^{-7}$. The results for the $\ddot{I}{„}^{-}\to \bar{p}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ and $\ddot{I}{„}^{-}\to p\hat{I}{¼}^{-}\hat{I}{¼}^{-}$ decay modes represent the first direct experimental limits on these channels.

20 pages, 10 figures, submitted to Physics Letters B