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

Abstract

We amalgamate the many experimental limits on the $ab\text{anti}b$ coupling of a light CP-odd Higgs boson, $a$, including model-dependence coming from the ratio of the $at\text{anti}t$ to the $ab\text{anti}b$ coupling. We then employ these limits to analyze the extent to which a light $a$ can make a significant contribution to the discrepancy, $\Delta a_{\mu }$, between the experimentally observed $a_{\mu }$ 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 $\Delta a_{\mu }$. The next-to-minimal supersymmetric model allows more freedom and the light $a$ of the model could explain the full $\Delta a_{\mu }$ if $9.2\text{gev}<\text{ma}<12\text{gev}$, or contribute substantially for larger $\text{ma}$, if $\text{tanb}$ is large.

Comments: 12 pages, 6 figures, revised and expanded