The charm-quark contribution to epsilon_K and Delta M_K

TL;DR

This paper presents a precise NNLO QCD calculation of the charm-quark contribution to neutral Kaon mixing, significantly refining the standard-model prediction of epsilon_K and enhancing its role in constraining new physics models.

Contribution

The paper provides the first NNLO calculation of eta_cc, revealing a 36% shift from NLO results, which improves the accuracy of epsilon_K predictions in the standard model.

Findings

Eta_cc = 1.87(76) from NNLO calculation

Standard-model prediction of |epsilon_K| = 1.81(28) x 10^-3

Significant 36% shift from previous NLO results

Abstract

Neutral Kaon mixing plays an important role in the phenomenology of the standard model and its extensions because of its sensitivity to high-energy scales. In particular epsilon_K, parameterising indirect CP violation in the neutral Kaon system, serves as an important constraint on models of new physics and is well suited for the indirect search for heavy new particles. In order to exploit this potential, a precise prediction of the standard-model background is crucial. I give a short summary of the standard-model prediction of epsilon_K, and present our recent NNLO QCD calculation of the charm-quark contribution eta_cc to the |Delta S| = 2 effective Hamiltonian. We find a large 36% shift with respect to the NLO value that leads to eta_cc = 1.87(76), shifting the standard-model prediction to |epsilon_K| = 1.81(28) x 10^-3.