CONSTRAINTS ON THE MINIMAL SUPERGRAVITY MODEL FROM THE B-]S-GAMMA DECAY

The constraints on the minimal supergravity model from the b→sγ decay are studied. A large domain in the parameter space for the model satisfies the CLEO bound B(b→sγ)<5.4×10-4. However, the allowed domain is expected to diminish significantly with an improved bound on this decay. The dependence of the b→sγ branching ratio on various parameters is studied in detail. It is found that, for At<0 and the top quark mass within the vicinity of the center of the CDF value mtpole=174±17 GeV, there exists only a small allowed domain because the light top squark is tachyonic for most of the parameter space. A similar phenomenon exists for a lighter top and At negative when the GUT coupling constant is slightly reduced. For At>0, however, the branching ratio is much less sensitive to small changes in mt and αG. © 1995 The American Physical Society.