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arXiv · 0910.5573

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

Hyung-Jin Kim·Taegil Bae·Jangho Kim·Jongjeong Kim·Kwangwoo Kim·Boram Yoon·Weonjong Lee·Chulwoo Jung·Stephen R. Sharpe
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Abstract

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. Our preliminary result from the SU(2) analysis is $B_K(\text{NDR}, \mu = 2 \text{GeV}) = 0.512 \pm 0.014 \pm 0.034$ and $\hat{B}_K = B_K(\text{RGI})= 0.701 \pm 0.019 \pm 0.047$. This is somewhat more accurate than our result from the SU(3) analysis. It is consistent with results obtained using valence domain-wall fermions

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Hyung-Jin Kim, Taegil Bae, Jangho Kim, Jongjeong Kim, Kwangwoo Kim, Boram Yoon, Weonjong Lee, Chulwoo Jung, Stephen R. Sharpe. 2009-10-29. Determination of $B_K$ using improved staggered fermions (II) SU(2) chiral perturbation theory fit. https://arxiv.org/abs/0910.5573

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