${\cal O}(\alpha_s^2)$ corrections to $b \to c$ decay at zero recoil

Abstract

Analytic formulae are presented for the two-loop perturbative QCD corrections to \(b \to c\) decay at the zero recoil point, which are required for the extraction of \(|V_{bc}|\) from measurements of exclusive \(B\to D^* l \nu\) decays. The results are in agreement with those in [8, 9]. Some comments on the numerical evaluation of the diagrams involved are made.