$\Upsilon\to\gamma A_1$ in the NMSSM at large tan beta

Abstract

We investigate the effects of the radiatively-generated tan beta-enhanced Higgs-singlet Yukawa couplings on the decay $\Upsilon\to \gamma A_1$ in the NMSSM, where $A_1$ is the lightest CP-odd scalar. This radiative coupling is found to dominate in the case of a highly singlet Higgs pseudoscalar. The branching ratio for the production of such a particle is shown to be within a few orders of magnitude of current experimental constraints across a significant region of parameter space. This represents a potentially observable signal for experiments at present B-factories.