Lepton Number Violation and Lepton Flavour Violation at LHCb

Abstract

Searches for heavy Majorana neutrinos in B− decays with final states containing hadrons plus a μ−μ− pair are performed using 0.41 fb−1 of data collected with the LHCb detector in proton-proton collisions at a center-of-mass energy of 7 TeV. No signals are found and upper limits are set on Majorana neutrino production and B− decay branching fractions as a function of the Majorana neutrino mass.A search is also made for the lepton flavour violating decay τ → μ+μ−μ− using 1.0 fb−1 of data collected by LHCb in 2011. The observed number of events is consistent with the background expectation, and an upper limit on the branching ratio is set. Using a similar procedure, the lepton flavour violating and baryon number violating decays τ− → p̄μ+μ− and τ− → pμ−μ− are searched for, and upper limits provided at 95% confidence level.