Resonant CP violation in rare τ± decays

In this work, we study the lepton number violating tau decays via intermediate on-shell Majorana neutrinos Nj into two scalar mesons and a lepton τ± → M1±Nj → M1±M2±ℓ∓. We calculate the Branching ratios Br(τ±) and the CP asymmetry (Γ(τ+) − Γ(τ−))/(Γ(τ+) + Γ(τ−)) for such decays, in a scenario that contains at least two heavy Majorana neutrinos. The results show that the CP asymmetry is small, but becomes comparable with the branching ratio Br(τ±) when their mass difference is similar with their decay width ΔMN ∼ ΓN. We also present regions of the heavy-light neutrino mixing elements, in which the CP asymmetry could be explored in future tau factories.