BK from the lattice with Wilson quarks

TL;DR

This paper presents lattice QCD calculations of the bag-parameter BK using Wilson fermions, achieving a result that accounts for operator mixing without subtractions, with implications for understanding CP violation in kaon mixing.

Contribution

The study introduces a method to compute BK on the lattice without subtracting mixing with other operators, improving accuracy in quenched Wilson fermion simulations.

Findings

BK = 0.96 +/- 0.10 in RG invariant form

Performed simulations at three lattice spacings

Method avoids operator mixing subtractions

Abstract

We report our results for the bag-parameter BK obtained from the quenched simulations on the lattice with Wilson fermions at three values of the lattice spacing. We implemented the method by which no subtraction of the mixing with other four-fermion dS=2 operators is needed. Our final result, in terms of the renormalisation group invariant bag-parameter, is BK = 0.96 +/- 0.10.