Matrix elements of (delta S=2) operators with Wilson fermions

TL;DR

This paper evaluates a Ward identity-based method for calculating K0-K0bar mixing amplitudes with Wilson fermions, finding consistent results without the need for lattice subtractions, and reports preliminary matrix element values.

Contribution

It introduces and tests a Ward identity approach to compute mixing amplitudes with Wilson fermions, avoiding spurious subtractions and providing preliminary matrix element results.

Findings

No difference observed with or without subtractions in simulations.

Preliminary matrix element results in the MS(NDR) scheme.

Method simplifies calculations of mixing amplitudes.

Abstract

We test the recent proposal of using the Ward identities to compute the K0-K0bar mixing amplitude with Wilson fermions, without the problem of spurious lattice subtractions. From our simulations, we observe no difference between the results obtained with and without subtractions. In addition, from the standard study of the complete set of (delta S=2) operators, we quote the following (preliminary) results (in the MS(NDR) scheme): Bk(2 GeV)=0.70(10), < O7^{3/2}>_{K->pi pi} = 0.10(2)(1) GeV^3, < O8^{3/2}>_{K->pi pi} = 0.49(6)(0) GeV^3.