Determination of $B_K$ using improved staggered fermions (II) SU(2) chiral perturbation theory fit

Understand

We present results for $B_K$ calculated using HYP-smeared improved staggered fermions on the MILC asqtad lattices.

• In this report, the data is analyzed using the results of SU(2) staggered chiral perturbation theory (SChPT).
• We outline the derivation of the NLO SU(2) SChPT result, explain our fitting procedure, and outline how we estimate systematic errors.
• We also show the light sea-quark mass and lattice spacing dependence for both SU(2) and SU(3)-based analyses.