The 27-plet contributions to the CP-conserving $K\rightarrow \pi l^+l^-$ decays

TL;DR

This paper analyzes the contribution of the 27-plet to rare kaon decays $K o \pi l^+l^-$ using one-loop SU(3) Chiral Perturbation Theory, showing it impacts decay rates and spectra by about 10%.

Contribution

It provides the first detailed estimate of the 27-plet's impact on $K o \pi l^+l^-$ decays within chiral perturbation theory, refining theoretical predictions.

Findings

27-plet contributes approximately 10% to branching ratios.

The 27-plet influences the shape of decay spectra.

The contribution aligns with current experimental spectra.

Abstract

We revisit the the rare kaon decays $K\to \pi l^+l^-$ which are of interest specially due to the recent measurements of the charged kaon decay spectra. We compute the contribution of the 27-plet to the decay amplitudes in one loop SU(3) Chiral Perturbation Theory. We estimate the resulting impact to be $\sim 10%$ to the branching ratios of the charged kaon decays, and also noticeably influence the shape of the spectra. With current values of the constants $G_8$ associated with the octet and $G_{27}$ associated with the 27-plet, the contribution of the latter pushes the spectrum in the correct direction for the charged lepton spectra. We also discuss the impact for the neutral decay rates and spectra.