Precision predictions for $B \rightarrow \rho \tau \nu_\tau$ and $B \rightarrow \omega \tau \nu_\tau$ 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 $B \rightarrow \rho \tau \nu_\tau$ and $B \rightarrow \omega \tau \nu_\tau$ 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.