The chromomagnetic dipole operator and the B semileptonic branching ratio

We consider the possibility of having a large branching ratio for the decay b --> sg coming from an enhanced Wilson coefficient of the chromomagnetic dipole operator. We show that values of BR(b --> sg) up to similar to 10% or more are compatible with the constraints coming from the CLEO experimental results on BR(B --> X(s) gamma) and BR(B --> X(s) phi). 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 --> sg).