Implications of the HyperCP Data on $B$ and $\tau$ decays

Abstract

If the HyperCP three events for the decay of ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$ are explained by a new pseudoscalar (axial-vector) boson $X_{P(A)}$ with a mass of 214.3 MeV, we study the constraints on the couplings between $X_{P(A)}$ and fermions from the experimental data in $K$ and $B$ processes. Some implications of the new particle on flavor changing $B$ and $\tau$ decays are given. Explicitly, we show that the decay branching ratios of $B_s\to \varphi X_{P(A)}\to \varphi {\mu }^{+}{\mu }^{-}$, $B_d\to K_0^{\ast }(1430)P(A)\to K_0^{\ast }(1430){\mu }^{+}{\mu }^{-}$ and $\tau \to \mu X_{P(A)}\to \mu {\mu }^{+}{\mu }^{-}$ can be as large as $2.7(2.8)\times 10^{-6}$, $7.4(7.5)\times 10^{-7}$ and $1.7(0.14)\times 10^{-7}$, respectively.

Comments: 12+1 pages, references added, version to appear in Phys. Lett. B