Testing improved staggered fermions with $m_s$ and $B_K$

TL;DR

This paper investigates the effectiveness of hypercubically smeared (HYP) improved staggered fermions in quenched QCD, specifically measuring the strange quark mass and kaon B-parameter to demonstrate reduced discretization errors.

Contribution

The study provides the first calculation of $m_s$ and $B_K$ using HYP-smeared staggered fermions, showing significant reduction in discretization errors compared to unimproved methods.

Findings

Measured $m_s$ as 101.2 MeV with errors.

Determined $B_K$ as 0.578 with errors.

Improvement reduces discretization errors in $B_K$.

Abstract

We study the improvement of staggered fermions using hypercubically smeared (HYP) links. We calculate the strange quark mass and the kaon B-parameter, $B_K$, in quenched QCD on a $16^3 \times 64$ lattice at $\beta=6.0$. We find $m_s(\bar{\rm MS},2 {\rm GeV})=101.2\pm1.3\pm4 $MeV and $B_K(\bar{\rm MS},2 {\rm GeV}) = 0.578 \pm 0.018\pm 0.042$, where the first error is from statistics and fitting, and the second from using one-loop matching factors. The scale ($1/a=1.95$GeV) is set by $M_\rho$, and $m_s$ is determined using the kaon mass. Comparing to quenched results obtained using unimproved staggered fermions and other discretizations, we argue that the size of discretization errors in $B_K$ is substantially reduced by improvement.