We analyze the anomalous magnetic moment of the muon $a_{\mu }$ in supersymmetric scenarios. First we concentrate on scenarios with universal soft terms. We find that a moderate increase of $a_{\mu }$ can be obtained by lowering the unification scale $M_{\mathrm{GUT}}$ to intermediate values of ${10}^{10}$ to ${10}^{12}\hspace{0.5em}\mathrm{GeV}.$ However, large values of $\tan \beta$ are still favored. Then we study the case of nonuniversal soft terms. For the usual value $M_{\mathrm{GUT}}\approx {10}^{16}\hspace{0.5em}\mathrm{GeV},$ we obtain $a_{\mu }$ in the favored experimental range even for moderate $\tan \beta$ regions $\left(\tan \beta \gtrsim 5\right).$ Finally, we give an explicit example of these scenarios. In particular, we show that in a D-brane model, where the string scale is naturally of the order of ${10}^{10}$ to ${10}^{12}\hspace{0.5em}\mathrm{GeV}$ and the soft terms are nonuniversal, $a_{\mu }$ is enhanced with low $\tan \beta .$

• Received 18 May 2001

DOI:https://doi.org/10.1103/PhysRevD.64.093012