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

Stringent relations between the B (*) -> D (*) form factors exist in the heavyquark 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 (*) l 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((-1.3) (+1.2)) 10(-3) using input from Light Cone Sum Rules, and R(D*) = 0: 260(8).