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

TL;DR

This paper analyzes experimental inputs and theoretical form factors for exclusive semileptonic B decays to pions and rhos, predicting observables within the Standard Model and exploring potential new physics effects.

Contribution

It provides a comprehensive analysis of form factors, defines fit scenarios, predicts observables, and assesses new physics sensitivities in B to pi/rho semileptonic decays.

Findings

Predicted various observables in the Standard Model.

Identified potential for sizeable new physics contributions.

Provided bounds on new physics Wilson coefficients.

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.