Axion-like particle-meson production in semileptonic $\ddot{I}„$ decays

Abstract

In this work we explore the semileptonic $\ddot{I}„$ decays into the axion-like particle ($a$)-meson final states within chiral effective field theory. The next-to-leading-order mixing matrix for the $\ddot{I}{€}^0$-$\hat{I}\cdot$-$\hat{I}{\cdot }^{\prime }$-$a$ system with the linear isospin-breaking effects, is exploited and then implemented to calculate the hadronic form factors relevant to the $\ddot{I}„$ decays. The resonance parameters entering the form factors are determined from fits to the experimental spectra of $\ddot{I}{„}^{-}\to \ddot{I}{€}^{-}\ddot{I}{€}^0\hat{I}{½}_{\ddot{I}}„$, $\ddot{I}{„}^{-}\to K_S\ddot{I}{€}^{-}\hat{I}{½}_{\ddot{I}}„$, and $\ddot{I}{„}^{-}\to K^{-}\hat{I}\cdot \hat{I}{½}_{\ddot{I}}„$. We then focus on the predictions to the branching ratios, invariant-mass distributions, and forward-backward asymmetries from the $\ddot{I}{„}^{-}\to Pa\hat{I}{½}_{\ddot{I}}„$ processes, with $P=\ddot{I}{€}^{-}$ and $K^{-}$. Our results provide a quantitative basis for future searches of the axion-like particle signals in semileptonic $\ddot{I}„$ decays.

9 pages, 2 figures, contributions to The 7th International Workshop on Future Tau-Charm Facilities (FTCF2025)