Two-Loop SUSY Corrections to the Anomalous Magnetic Moment of the Muon

We calculate supersymmetric two-loop corrections to the anomalous magnetic moment of the muon, consisting of diagrams with a closed scalar fermion or fermion loop and gauge and/or Higgs boson exchange. We discuss the numerical impact of each subclass of diagrams and determine the leading contributions. We analyze in detail constraints from experimental information on the Higgs boson mass, Delta(rho), and the branching ratios of B -> X_s gamma and B_s -> mu^+ mu^-. If these constraints are taken into account, the largest possible contributions are reduced from more than 2 sigma (in terms of the current experimental error) to ~0.3 sigma. The only exceptions arise in rather extreme parameter scenarios with a strong non-universality between the soft breaking parameters in the stop and sbottom sectors.