$B\to \rho l\bar{\nu }$ and $\omega l\bar{\nu }$ in and beyond the Standard Model: Improved predictions and $|V_{ub}|$

Abstract

We revisit the experimental and theoretical status of $B\to \rho l\bar{\nu }$ and $B\to \omega l\bar{\nu }$ decays. We perform a combined fit of averaged spectra from Belle and Babar measurements with prior light cone sum rule calculations, in order to obtain more precise predictions over the full $q^2$ range. The extracted values of $|V_{ub}|$ from these combined fits exhibit smaller uncertainty compared to previous extractions from $B\to \rho l\bar{\nu }$ and $B\to \omega l\bar{\nu }$ decays and the central values are found to be smaller than values extracted from $B\to \pi l\nu$ or inclusive measurements. We use our fit results to obtain more precise predictions in and beyond the Standard Model for the lepton universality ratios $R(\rho )$ and $R(\omega )$, as well as several angular observables that are sensitive to the full $q^2$ distribution, such as the longitudinal polarization of the vector meson, the $\tau$ polarization, and its forward-backward asymmetry.

Comments: Fixes and clarifies sign convention of tau polarization in Table V