A closer look at observables from exclusive semileptonic $B\to(\pi,\rho)\ell\nu_{\ell}$ decays

Abstract

This article analyses the available inputs in $\btopilnu$ and $\btorholnu$ decays which include the measured values of differential rate in different $q^2$-bins (lepton invariant mass spectrum), lattice, and the newly available inputs on the relevant form-factors from the light-cone sum rules (LCSR) approach. We define different fit scenarios, and in each of these scenarios, we predict a few observables in the standard model (SM). For example, $R(M) =\frac{\mathcal{B}(B \to M\ell_i\nu_{\ell_i})}{\mathcal{B}(B\to M\ell_j\nu_{\ell_j})} $, $R^{\ell_i}_{\ell_j}(M) =\frac{\mathcal{B}(B\to \ell_i\nu_{\ell_i})}{\mathcal{B}(B \to M\ell_j\nu_{\ell_j})}$ with M = $\pi$ or $\rho$ and $\ell_{i,j} = e, \mu$ or $\tau$. We also discuss the new physics (NP) sensitivities of all these observables and obtain bounds on a few NP Wilson coefficients in $b\to u \tau\nu_{\tau}$ decays using the available data. We have noted that the data at present allows sizeable NP contributions in this mode. Also, we have predicted a few angular observables relevant to these decay modes.