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 $B_{ s}\to\phi X_{ P(A)}\to \phi\mu^{ +}\mu^{ -}$, $B_{ d}\to K_{ 0}^{ *}(1430){ P(A)}\to K_{ 0}^{ *}(1430)\mu^{ +}\mu^{ -}$ 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.
Categories: hep-ph hep-ex