B-> D* zero-recoil formfactor and the heavy quark expansion in QCD: a systematic study

TL;DR

This paper provides a detailed QCD analysis of the B -> D* zero-recoil form factor, incorporating advanced perturbative corrections and higher-order power corrections, resulting in a refined prediction that impacts semileptonic B decay understanding.

Contribution

It introduces a systematic, model-independent approach to estimate inelastic contributions and higher-order corrections in the heavy quark expansion for B meson decays.

Findings

Predicted F_D*(1) value around 0.86

Large inelastic contributions linked to hyperfine splitting

Enhanced yield of excited charm states in B decays

Abstract

We present a QCD analysis of heavy quark mesons focussing on the B -> D* formfactor at zero recoil, F_D*(1). An advanced treatment of the perturbative corrections in the Wilsonian approach is presented. We estimate the higher-order power corrections to the OPE sum rule and describe a refined analysis of the nonresonant continuum contribution. In the framework of a model-independent approach, we show that the inelastic contribution in the phenomenological part of the OPE is related to the mQ-dependence of the hyperfine splitting and conclude that the former is large, lowering the prediction for F_D*(1) down to about 0.86. This likewise implies an enhanced yield of radial and D-wave charm excitations in semileptonic B decays and alleviates the problem with the inclusive yield of the wide excited states. We also apply the approach to the expectation values of dimension 7 and 8 local operators and to a few other issues in the heavy quark expansion.