R(D ∗), |Vcb|, and the Heavy Quark Symmetry relations between form factors

Abstract

Stringent relations between the B(∗) → 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 → D(∗)ℓν with model-independent parametrizations and in the related prediction of R(D(∗)). We find |Vcb| = 41.5(1.3) 10−3 and |Vcb| = 40.6(− 1.3+ 1.2) 10−3 using input from Light Cone Sum Rules, and R(D∗) = 0.260(8).