Lattice matrix elements confronting the experimental value of eps'/eps

TL;DR

This paper discusses a new lattice calculation of K to 2 pi transitions that challenges previous results, highlighting potential conflicts with experimental measurements of epsilon'/epsilon and implications for new physics in kaon decays.

Contribution

It analyzes the conditions under which the lattice estimate of the hadronic matrix element can be reconciled with experimental data, questioning previous assumptions.

Findings

Lattice estimate suggests an opposite sign for the Q6 matrix element.

The magnitude of the matrix element is significantly larger than the vacuum saturation approximation.

Reconciling lattice results with experiments may require new physics beyond current models.

Abstract

A new lattice estimate of K -> 2 pi transitions claims, contrary to all other computations, that the hadronic matrix element for the gluon penguin operator Q_6 has opposite sign and, in addition, is much larger than the vacuum saturation approximation. We comment under what conditions (if any) it is possible to reconcile this lattice result with the experimental value of eps'/eps. The dramatic impact of new physics in the kaon system that seems to be required is not easily accommodated within our present theoretical understanding.