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Constraints on the new particle in $Σ^+\to pμ^+μ^-$

C. Q. Geng·Y. K. Hsiao
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Abstract

The HyperCP collaboration has presented the branching ratio of $Σ^+\to pμ^+μ^-$ to be $(8.6^{+6.6}_{-5.4}\pm 5.5)\times 10^{-8}$ and suggested a new boson $P^0$ with a mass of $214.3\pm 0.5$ MeV to induce the flavor changing transition of $s\to dμ^+μ^-$. We demonstrate that to explain the data, the new particle cannot be a scalar but pseudoscalar based on the direct constraints from $K^+\toπ^+μ^+μ^-$ and $K_L\toμ^+μ^-$, 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.

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C. Q. Geng, Y. K. Hsiao. 2005-10-26. Constraints on the new particle in $Σ^+\to pμ^+μ^-$. https://doi.org/10.1016/j.physletb.2005.10.056

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