B -> D* at zero recoil revisited

TL;DR

This paper revisits the B to D* form factor at zero recoil using continuum QCD and heavy quark sum rules, refining calculations and estimating inelastic contributions to provide an unbiased value of approximately 0.86.

Contribution

It provides a model-independent estimate of the B to D* form factor at zero recoil, incorporating refined radiative corrections and inelastic contributions.

Findings

Upper bound on F(1) < 0.93

Inelastic contributions reduce F(1) by about 6% or more

Estimated F(1) ≈ 0.86 with 3% uncertainty

Abstract

We examine the B -> D* form factor at zero recoil using a continuum QCD approach rooted in the heavy quark sum rules framework. A refined evaluation of the radiative corrections as well as the most recent estimates of higher order power terms together with more careful continuum calculation are included. An upper bound on the form factor of F(1)< 0.93 is derived, based on just the positivity of inelastic contributions. A model-independent estimate of the inelastic contributions shows they are quite significant, lowering the form factor by about 6% or more. This results in an unbiased estimate F(1) \approx 0.86 with about three percent uncertainty in the central value.