Looking for possible new physics in $B\to D^{(\ast)}\tau\nu_{\tau}$ in light of recent data

TL;DR

This paper analyzes $B o D^{(*)} au u$ decays using recent experimental data, fitting form-factors without new physics, then exploring potential new physics operators, finding vector currents best explain the data.

Contribution

It provides a data-driven analysis of form-factors and identifies the vector current operator as the most plausible new physics contribution in $B$ decays.

Findings

Discrepancy in $q^2$-distributions of pseudo-vector form-factors.

Vector current operators best fit the experimental data.

Form-factors from different decay modes show partial inconsistency.

Abstract

We study the decays $B\to D^{(\ast)}\tau\nu_{\tau}$ in light of the available data from BABAR, Belle and LHCb. We divide our analysis into two parts: in one part we fit the form-factors in these decays directly from the data without adding any additional new physics (NP) contributions and compare our fit results with those available from the decays $B\to D^{(\ast)}\ell\nu_{\ell}$. We find that the $q^2$-distributions of the form-factors associated with the pseudo-vector current, obtained from $B\to D^{(\ast)}\tau\nu_{\tau}$ and $B\to D^{(\ast)}\ell\nu_{\ell}$ respectively, do not agree with each other, whereas the other form-factors are consistent with each other. In the next part of our analysis, we look for possible new effective operators of dimension 6 amongst new vector, scalar, and tensor-type that can best explain the current data in the decays $B\to D^{(\ast)}\tau\nu_{\tau}$. We use the information-theoretic approaches, especially of `Second-order Akaike Information Criterion' (AIC$_c$) in the analysis of empirical data. Normality tests for the distribution of residuals are done after selecting the best possible scenarios, for cross-validation. We find that it is the contribution from the operator involving left or right-handed vector current that passes all the selection criteria defined for the best-fit scenario and can successfully accommodate all the available data set.