One-loop matching of Delta S=2 four-quark operators with improved staggered fermions

TL;DR

This paper calculates one-loop matching coefficients for Delta S=2 four-quark operators using improved staggered fermions, enabling more precise lattice QCD determinations of B_K relevant for CP violation studies.

Contribution

It provides the first O(alpha_s) perturbative matching coefficients for these operators with the Asqtad improved staggered action, aiding unquenched B_K calculations.

Findings

Matching coefficients computed for improved staggered fermions.

Results facilitate unquenched B_K determination from lattice simulations.

Enhances precision in CP violation parameter estimation.

Abstract

We compute O(alpha_s) lattice-to-continuum perturbative matching coefficients for the Delta S=2 flavor changing four-quark operators for the Asqtad improved staggered action. In conjunction with lattice simulations with three flavors of light, dynamical quarks, our results yield an unquenched determination of B_K, the parameter that determines the amount of indirect CP violation in the neutral kaon system. Its value is an important input for the unitarity triangle analysis of weak decays.