Does the HyperCP Evidence for the DecayΣ+→pμ+μ−Indicate a Light Pseudoscalar Higgs Boson?

The HyperCP Collaboration has observed three events for the decay ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$ which may be interpreted as a new particle of mass 214.3 MeV. However, existing data from kaon and $B$-meson decays provide stringent constraints on the construction of models that support this interpretation. In this Letter we show that the “HyperCP particle” can be identified with the light pseudoscalar Higgs boson in the next-to-minimal supersymmetric standard model, the $A_1^0$. In this model there are regions of parameter space where the $A_1^0$ can satisfy all the existing constraints from kaon and $B$-meson decays and mediate ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$ at a level consistent with the HyperCP observation.