No-scale scenarios in the light of new measurement of muon anomalous magnetic moment

Supersymmetric contribution to the muon anomalous magnetic moment a(mu) is discussed in the no-scale-type supersymmetry breaking scenarios. Taking the correlation between the supersymmetric contributions to a(mu) and Br(b --> s gamma), it is shown that the precise measurements of these quantities serve an important constraint on the relative sign of the gaugino masses: combining the 2.6 sigma deviation in a(mu) from the standard-model prediction measured by the E821 experiment and Br(b --> s gamma) measured by CLEO, the sign of the product M2M3 is strongly preferred to be positive, where M-2 and M-3 are SU(2)(L) and SU(3)(C) gaugino mass parameters, respectively. In particular, no-scale-type models with universal gaugino masses are in accord with the two constraints and also with the Higgs mass bound. In addition, it is also shown that future improvements in the measurements of a(mu) and Br(b --> s gamma) may provide serious test of the cases with M2M3 < 0. (C) 2001 Elsevier Science B.V. All rights reserved.