Searches for LFV and LNV Decays at LHCb

Abstract

The paper presents the latest progress on the searches for Lepton Number Violating (LNV) B Meson decays, the Lepton Flavour Violating (LFV) decay $\Ptau^- \to \Pmu^-\Pmu^-\Pmu^+$, and the Lepton and Baryon Number Violating (LNV and BNV) decays $\Ptau^- \to \mu^+ \mu^- \APproton$ and $\Ptau^- \to \mu^- \mu^- \Pproton$ at the LHCb. These searches have been performed at a hadron collider for the first time. In the absence of signal we put upper limits, which are as follows: $\mathcal{B}(\tau^- \to \mu^- \mu^- \mu^+) < 6.3 \times 10^{-8}$, $\mathcal{B}(\Ptau^- \to \mu^- \mu^+ \APproton) < 3.4 \times 10^{-7}$, $\mathcal{B}(\Ptau^- \to \mu^- \mu^- \Pproton) < 4.4 \times 10^{-7}$ at 90% CL.