# Anomalies in (semi)-leptonic $B$ decays $B^{\pm} \to \tau^{\pm} \nu$, $B^{\pm} \to D \tau^{\pm} \nu$ and $B^{\pm} \to D^* \tau^{\pm} \nu$, and possible resolution with sterile neutrino

## TL;DR

This paper investigates anomalies in semileptonic B decays involving tau leptons, proposing sterile neutrinos as a possible explanation for deviations from Standard Model predictions and exploring future experimental tests at Belle-II.

## Contribution

It introduces sterile neutrino scenarios to explain anomalies in B decay ratios and evaluates new ratios for future experimental validation.

## Key findings

- Sterile neutrinos can account for observed anomalies in $R(D^{(*)})$.
- Predicted ratios align with current experimental deviations.
- Future measurements at Belle-II can test the sterile neutrino hypothesis.

## Abstract

The universality of the weak interactions can be tested in semileptonic $b \to c$ transitions, and in particular in the ratios $R(D^{(*)}) \equiv \Gamma(B \rightarrow D^{(*)} \tau \nu )/\Gamma(B \rightarrow D^{(*)} \ell \nu )$ (where $\ell = \mu$ or $e$). Due to the recent differences between the experimental measurements of these observables by BaBar, Belle and LHCb on the one hand and the Standard Model predicted values on the other hand, we study the predicted ratios $R(D^{(*)}) = \Gamma(B \rightarrow D^{(*)} \tau +$ "missing" $)/\Gamma(B \rightarrow D^{(*)} \ell \nu )$ in scenarios with an additional sterile heavy neutrino of mass $\sim 1$ GeV. Further, we evaluate the newly defined ratio $R(0) \equiv \Gamma(B \to \tau +$ "missing" $)/\Gamma(B \to \mu \nu )$ in such scenarios, in view of the future possibilities of measuring the quantity at Belle-II.