Angular and polarization observables for Majorana-mediated B decays with effective interactions

Abstract

We probe the effective field theory extending the Standard Model with a sterile neutrino in B meson decays at B factories and lepton colliders, using angular and polarization observables. We put bounds on different effective operators characterized by their distinct Dirac–Lorentz structure, and probe the N-mediated B decays sensitivity to these interactions. We define a forward–backward asymmetry A_mathrm{FB}^{ell gamma } between the muon and photon directions for the B rightarrow mu nu gamma decay, which allows us to separate the SM contribution from the effective lepton number conserving and violating processes, mediated by a near on-shell N. Using the most stringent constraints on the effective parameter space from Belle and BaBar we find that a measurement of the final polarization P_{tau } in the rare B^-rightarrow ell ^-_{1}ell ^-_{2} pi ^+ decays can help us infer the scalar or vector interaction content in the N production or decay vertices. We find that the B meson decays are more sensitive to scalar operators.