A measurement of the inclusive branching ratio for $b \to s\gamma$ with the ALEPH detector at LEP

In a data sample of approximately four million hadronic Z0 decays, recorded by the ALEPH detector during the years 1991 to 1995, the inclusive branching ratio for b -> s gamma is measured to be: Br(b -> s gamma) = (3.14 +- 0.83 +- 0.53) x 10^-4, where the first error is statistical and the second error systematic. This decay rate is consistent with that expected from Standard Model penguin diagrams.