Searches for lepton flavour violation and lepton number violation at LHCb

Searches for lepton flavour and lepton number violating decays at LHCb are presented in various τ and D decays. Lepton flavour violating decays are forbidden in the Standard Model, they are considered as a probe for New Physics. Those searches are performed using pp collision data recorded by LHCb experiment in 2011. In addition searches for Majorana neutrinos in B+ decays with like-sign μ pair in the final states are summarized. No signal was observed at 95% confidence level for all these decays. Upper limits are set on the branching fractions of corresponding decay modes.