Constraints on Supergravity in the Light Gluino Scenario

Minimal $N=1$ supergravity with a radiatively broken electroweak symmetry group is studied in the light gluino scenario. Constraints from the $b\to s\gamma$ decay and from the masses of the light CP-even neutral Higgs $m_h$, the lightest chargino $m_{{\chi }_1^{\pm }}$, and the second lightest neutralino $m_{{\chi }_2^0}$ are analyzed. We consider models in which the relation $A=B+m_0$ holds. We plot the allowed region in the $\tan \beta -\mu$ plane consistent with chargino/neutralino searches, and an upper bound on $\tan \beta$ given by 1.82 (1.85) for $\mu >0$ ($\mu <0$) is found. We analize the consistency of this upper bound with experimental constraints on the lightest Higgs mass. We find that a gluino with a mass of a few GeV is incompatible with this kind of models.