A light CP-odd Higgs boson and the muon anomalous magnetic moment

Abstract

We amalgamate the many experimental limits on the ab coupling of a light CP-odd Higgs boson, a, including model-dependence coming from the ratio of the at to the ab coupling. We then employ these limits to analyze the extent to which a light a can make a significant contribution to the discrepancy, Δaμ, between the experimentally observed aμ and that predicted by the standard model. In a ``model-independent'' framework and in the context of a general two-Higgs-doublet model this is a significant possibility. In contrast, the minimal supersymmetric model is too strongly constrained (after combining experimental and theoretical input) to allow a CP-odd-a explanation of Δaμ. The next-to-minimal supersymmetric model allows more freedom and the light a of the model could explain the full Δaμ if 9.2 GeV < ma < 12 GeV, or contribute substantially for larger ma, if tan β is large.