$\varepsilon'/\varepsilon$ in and beyond the Standard Model

Abstract

Estimates of the CP violating observable $\varepsilon'/\varepsilon$ have gained some attention in the past few years. Depending on the long-distance treatment used, they exhibit up to $2.9σ$ deviation from the experimentally measured value. Such a deviation motivates the investigation of New Physics (NP) effects in the process $K\toππ$. In my talk I will review the Standard Model (SM) prediction for $\varepsilon'/\varepsilon$, with a special focus on the Dual QCD approach. On the NP side, I will discuss a recent computation of the hadronic matrix elements of NP operators. Furthermore a master formula for BSM effects in $\varepsilon'/\varepsilon$ is presented. Finally, a treatment of $\varepsilon'/\varepsilon$ using the SM effective theory (SMEFT) will be discussed together with possible correlations to other observables.

10 pages, Proceedings of the 10th International Workshop on the CKM Unitarity Triangle (CKM 2018), Heidelberg, Germany, 17-21 September 2018