Study of the decay b-->sg gamma in the standard model.

Abstract

We consider the decay b\ensuremath{\rightarrow}sg\ensuremath{\gamma} (where the gluon is hard) in the standard model. For a reasonable choice of the t-quark mass ${\mathit{m}}_{\mathit{t}}$, we find that it has a branching ratio approximately of the order ${10}^{\mathrm{\ensuremath{-}}5}$--${10}^{\mathrm{\ensuremath{-}}6}$. Moreover, for different values of ${\mathit{m}}_{\mathit{t}}$, the polarization of the photon is different. An accurate measurement on the photon polarization should, therefore, provide some useful information on ${\mathit{m}}_{\mathit{t}}$. In addition, a CP-violating asymmetry parameter related to the correlation between the photon polarization and the decay plane is shown to be of the order of a few percent. This provides an effect which is accessible to the future high-luminosity B factories, but obviously poses a challenge.