Precision predictions for $B\to \rho \tau {\nu }_{\tau }$ and $B\to \omega \tau {\nu }_{\tau }$ in the SM and beyond

Abstract

We present new precision predictions for semitauonic decays involving $\rho$ and $\omega$ final state mesons. These decay channels offer an interesting orthogonal probe to study the existing B anomalies in semitauonic transitions and are accessible with the Belle II experiment. The predictions are based on combining existing light-cone sum-rule calculations for the form factors with measured experimental spectra from the BaBar and Belle collaborations. This allows us to reliably extrapolate the light-lepton form factor predictions to large values of the four-momentum transfer squared, $q^2$, and in turn to derive precise predictions for $R_{\rho }$ and $R_{\omega }$, the ratio of the total decay rates of $B\to \rho \tau {\nu }_{\tau }$ and $B\to \omega \tau {\nu }_{\tau }$ for $\tau$ final states with respect to light leptons in the SM. In addition, we investigate the impact of all four-fermi operators on the semitauonic $q^2$ spectra and these ratios.

Comments: Contribution to the European Physical Society Conference on High Energy Physics - EPS-HEP2019