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

TL;DR

This paper investigates how angular and polarization observables in B meson decays can reveal the nature of effective interactions involving sterile neutrinos, providing bounds and sensitivity analyses based on experimental data.

Contribution

It introduces a novel approach using angular and polarization measurements to distinguish between different effective operators in sterile neutrino mediated B decays.

Findings

B meson decays are more sensitive to scalar operators.

A forward-backward asymmetry helps separate SM and new physics contributions.

Polarization measurements can infer the nature of interactions involving sterile neutrinos.

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 $A_{FB}^{\ell \gamma}$ between the muon and photon directions for the $B \to \mu \nu \gamma$ 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.