Muon anomalous magnetic moment, two-Higgs-doublet model, and supersymmetry

The recent measurement of the muon anomalous magnetic moment a(mu) shows a 2.6 sigma deviation from the standard model value. We show that it puts strong constraints on the parameter space of the two-Higgs-doublet model (2HDM) II. The dominant contribution of the Higgs bosons comes at the mo-loop level. and in order to explain the data it favors a pseudoscalar A with a light mass range and a large tan beta. At 95% C.L., the upper limit for m(A) is 29 (55) (85) GeV for tan beta = 30 (45) (60), and tan beta is bounded below at 17. This is in sharp contrast to the conclusion one draws from considering one-loop Higgs contributions alone. Finally, we also discuss the role of the Higgs contributions in the minimal supersymmetric standard model.