The Muon Anomalous Magnetic Dipole Moment in the Minimal Supersymmetric Standard Model

TL;DR

This study computes the MSSM contributions to the muon anomalous magnetic moment $a_\mu$, showing that for large $\tan\beta$ the SUSY loop contributions from neutralino-smuon and chargino-sneutrino diagrams can reach $O(10^{-9})$ over broad MSSM parameter space. It derives analytic expressions and analyzes their behavior via mass insertion, highlighting the $\tan\beta$ enhancement and the sign dependence on $m_G\mu_H\tan\beta$. Numerical scans with $A_\mu=0$ reveal sensitivity to $m_{G2}$, $m_{\tilde{\mu}L}$, $m_{\tilde{\mu}R}$, and $\mu_H$, with implications for LEP bounds and potential observability by Brookhaven E821 even when sparticles are not collider-accessible. The results establish the muon MDM as a complementary, powerful probe of MSSM parameter space and non-universal scalar masses, with practical implications for constraining $\tan\beta$ and guiding future experiments.

Abstract

The muon anomalous magnetic dipole moment (MDM) is calculated in the framework of the minimal supersymmetric standard model (MSSM). In this paper, we discuss how the muon MDM depends on the parameters in MSSM in detail. We show that the contribution of the superparticle-loop becomes significant especially when $\tanβ$ is large. Numerically, it becomes $O(10^{-8}-10^{-9})$ in a wide parameter space, which is within the reach of the new Brookhaven E821 experiment.

Figures (1)

• Figure 1: Feynman diagrams which give rise to the muon MDM in the mass eigenstate basis. The external lines represent the muon (straight) and the photon (wavy).