Constraints on the new particle in ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$

Abstract

The HyperCP collaboration has presented the branching ratio of ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$ to be $(8.6_{-5.4}^{+6.6}\pm 5.5)\times 10^{-8}$ and suggested a new boson $P^0$ with a mass of $214.3\pm 0.5$ MeV to induce the flavor changing transition of $s\to d{\mu }^{+}{\mu }^{-}$. We demonstrate that to explain the data, the new particle cannot be a scalar but pseudoscalar based on the direct constraints from $K^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-}$ and $K_L\to {\mu }^{+}{\mu }^{-}$, respectively. Moreover, we determine that the decay width of the pseudoscalar should be in the range of $10^{-7}$ MeV with the lifetime of $10^{-14}$ sec.

Comments: 8 pages, 3 figures, 1 table, revised version to appear in Phys. Lett. B