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

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 $R(D^{ *})=0.260(8)$.

Categories: hep-ph