Probing supergravity models with indirect experimental signatures.

We explore the one-loop electroweak radiative corrections in the context of the traditional minimal SU(5) and the string-inspired SU(5) × U(1) supergravity models by calculating explicitly vacuum-polarization and vertexcorrection contributions to the ǫ1 and ǫb parameters. We also include in this analysis the constraint from b → sγ whose inclusive branching ratio B(b → sγ) has been actually measured very recently by CLEO. We find that by combining these three most important indirect experimental signatures and using the most recent experimental values for them, mt ∼ 170 GeV is excluded for μ > 0 in both the minimal SU(5) supergravity and the no-scale SU(5)×U(1) supergravity. We also find that mt ∼ 175 (185) GeV is excluded for any sign of μ in the minimal (SU(5)× U(1)) supergravity model. PACS numbers: 12.15.Ji, 04.65.+e, 12.60.Jv, 14.80.Ly Typeset using REVTEX 1