Kaon B-parameter with NF=2 dynamical Wilson fermions

TL;DR

This study investigates the kaon B-parameter using two-flavor dynamical Wilson fermions, employing novel methods to reduce uncertainties and examining its dependence on quark mass.

Contribution

It introduces the non-subtraction method for matrix element calculation and applies non-perturbative renormalization in a dynamical fermion setup.

Findings

Non-subtraction method yields smaller uncertainties.

Dependence of BK on heavy quark masses is negligible.

Preliminary BKRGI value is 1.02(25).

Abstract

We present a preliminary study of the neutral kaon mixing bag parameter BK using two flavors of dynamical Wilson fermions. We determine the matrix element of the relevant DeltaS=2 operator by using both the conventional approach and the so called ``non-subtraction method'', and find that the latter leads to results with smaller uncertainties. After having implemented non-perturbative renormalization, we study the dependence of BK on the see quark mass. At our relatively heavy values of quark masses (0.60<M_P/M_V<0.75) such a dependence is found to be negligible and the results, within the statistical accuracy, are consistent with a quenched determination. As a preliminary result for the renormalization group invariant parameter we quote BKRGI=1.02(25).