We calculate the kaon mixing B-parameters for operators arising generically in theories of physics beyond the standard model. We use HYP-smeared improved staggered fermions on the Nf=2+1 MILC asqtad lattices. Operator matching is done perturbatively at one-loop order. Chiral extrapolations are done using "golden combinations" in which one-loop chiral logarithms are absent. For the combined sea-quark mass and continuum extrapolation, we use three lattice spacings: a≈0.045,0.06 and 0.09fm. Our results have a total error of 5-6%, which is dominated by the systematic error from matching and continuum extrapolation. For two of the BSM B-parameters, we agree with results obtained using domain-wall and twisted-mass dynamical fermions, but we disagree by (4−5)σ for the other two.
@article{arxiv.1310.7372,
title = {Beyond the Standard Model B-parameters with improved staggered fermions in $N_f=2+1$ QCD},
author = {Taegil Bae and Yong-Chull Jang and Hwancheol Jeong and Jangho Kim and Jongjeong Kim and Kwangwoo Kim and Seonghee Kim and Weonjong Lee and Jaehoon Leem and Hyung-Jin Kim and Chulwoo Jung and Stephen R. Sharpe and Boram Yoon},
journal= {arXiv preprint arXiv:1310.7372},
year = {2013}
}