$R(D^*)$, $|V_{cb}|$, and the Heavy Quark Symmetry relations between form factors

TL;DR

This paper reevaluates the uncertainties in heavy quark symmetry relations between form factors and their impact on extracting |V_{cb}| and predicting R(D*), using model-independent parametrizations and recent Belle data.

Contribution

It provides a refined analysis of form factor relations and their uncertainties, improving the precision in determining |V_{cb}| and R(D*) from experimental data.

Findings

|V_{cb}| = 41.5(1.3) x 10^{-3} from Light Cone Sum Rules

|V_{cb}| = 40.6(+1.2/-1.3) x 10^{-3} from Belle data

R(D*) = 0.260(8) with updated analysis

Abstract

Stringent relations between the $B^{(*)} \to D^{(*)} $ form factors exist in the heavy quark limit and the leading symmetry breaking corrections are known. We reconsider their uncertainty and role in the analysis of recent Belle data for $B\to D^{(*)}\ell\nu$ with model-independent parametrizations and in the related prediction of $R(D^{(*)})$. We find $|V_{cb}|=41.5(1.3) \ 10^{-3}$ and $|V_{cb}|=40.6(^{+1.2}_{-1.3}) \ 10^{-3}$ using input from Light Cone Sum Rules, and $R(D^{*})=0.260(8)$.