The status of theoretical calculations of BR[\bar {B} \to Xs \gamma ] is discussed. It is pointed out that replacing mcpole/mbpole in the matrix element Xs \gamma | (\bar {s}c)V-A(\bar {c}b)V-A | b\rangle by the more appropriate mc\overline {MS}(\mu )/mbpole with \mu \in [mc,mb] causes an 11% enhancement of the SM prediction for the branching ratio, and has a sizeable effect on the uncertainty. However, the uncertainty can be maintained at the level of around 10% thanks to an observation that mb(\mu ) in the top-quark contribution to the decay amplitude is the main source of perturbative QCD effects in the considered process.
PACS numbers: 13.20.He
| Table of Contents | Back to Number 6 contents |