The Chromomagnetic Dipole Operator and the B Semileptonic Branching Ratio

Abstract

We consider the possibility of having a large branching ratio for the decay $b\to sg$ coming from an enhanced Wilson coefficient of the chromomagnetic dipole operator. We show that values of $BR(b\to sg)$ up to $\sim 10\%$ or more are compatible with the constraints coming from the CLEO experimental results on $BR(B\to X_s\gamma )$ and $BR(B\to X_s\varphi )$. Such large values can reconcile the predictions of both the semileptonic branching ratio and the charm counting with the present experimental results. We also discuss a supersymmetric model with gluino-mediated flavour violations, which can account for such large values of $BR(b\to sg)$.

Comments: 19 pages, 3 eps figures included, replacement with minor changes