Chargino contributions in light of recent $\epsilon'/\epsilon$

Abstract

Recently, the standard model prediction of $\epsilon'/\epsilon$ was improved, and a discrepancy from the experimental results was reported at the $2.9\sigma$ level. We study the chargino contributions to $Z$ penguin especially with the vacuum stability constraint. The vacuum decay rate is investigated, and it is shown that the discrepancy can be explained if superparticles are lighter than 4-6 TeV. Correlations with $\mathcal{B}(K_L\to\pi^0\nu\bar\nu)$ and other experimental constraints are also discussed.