Lepton number violation by heavy Majorana neutrino in B decays

Heavy Majorana neutrinos are predicted in addition to ordinary active neutrinos in the models with the seesaw mechanism. We investigate the lepton number violation (LNV) in B decays induced by such a heavy neutrino N with GeV-scale mass. Especially, we consider the decay channel B+→μ+N→μ+μ+π− and derive the sensitivity limits on the mixing angle Θμ by the future search experiments at Belle II and in e+e− collisions at the Future Circular Collider (FCC-ee).