Probing SUSY effects in $K_S^0\rightarrow\mu^+\mu^-$

TL;DR

This paper investigates how supersymmetric models, specifically the MSSM, can significantly alter the decay rate and CP asymmetry of the $K_S^0 ightarrow\mu^+\mu^-$ process, potentially reaching current experimental bounds.

Contribution

It provides the first detailed analysis of SUSY effects on $K_S^0 ightarrow\mu^+\mu^-$ decay, including enhancements, suppressions, and correlations within the MSSM framework.

Findings

SUSY can enhance the decay branching ratio up to 35 times the SM prediction.

SUSY can suppress the decay branching ratio down to 0.78 times the SM prediction.

Predicted CP asymmetry can be up to eight times larger than in the SM.

Abstract

We explore supersymmetric contributions to the decay $K_S^0\rightarrow\mu^+\mu^-$, in light of current experimental data. The Standard Model (SM) predicts $\mathcal{B}(K_S^0\rightarrow\mu^+\mu^-)\approx5\times 10^{-12}$. We find that contributions arising from flavour violating Higgs penguins can enhance the branching fraction up to $\approx 35\times 10^{-12}$ within different scenarios of the Minimal Supersymmetric Standard Model (MSSM), as well as suppress it down to $\approx 0.78\times 10^{-12}$. Regions with fine-tuned parameters can bring the branching fraction up to the current experimental upper bound, $8\times 10^{-10}$. The mass degeneracy of the heavy Higgs bosons in MSSM induces correlations between $\mathcal{B}(K_S^0\rightarrow\mu^+\mu^-)$ and $\mathcal{B}(K_L^0\rightarrow\mu^+\mu^-)$. Predictions for the $CP$ asymmetry in $K^0\rightarrow\mu^+\mu^-$ decays in the context of MSSM are also given, and can be up to eight times bigger than in the SM.