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arXiv · 0905.3947

The neutral kaon mixing parameter B_K from unquenched mixed-action lattice QCD

C. Aubin·Jack Laiho·Ruth S. Van de Water
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Abstract

We calculate the neutral kaon mixing parameter B_K in unquenched lattice QCD using asqtad-improved staggered sea quarks and domain-wall valence quarks. We use the "2+1" flavor gauge configurations generated by the MILC Collaboration, and simulate with multiple valence and sea quark masses at two lattice spacings of a ~ 0.12 fm and a ~ 0.09 fm. We match the lattice determination of B_K to the continuum value using the nonperturbative method of Rome-Southampton, and extrapolate B_K to the continuum and physical quark masses using mixed action chiral perturbation theory. The "mixed-action" method enables us to control all sources of systematic uncertainty and therefore to precisely determine B_K; we find a value of B_K^{MSbar, NDR}(2 GeV) = 0.527(6)(20), where the first error is statistical and the second is systematic.

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C. Aubin, Jack Laiho, Ruth S. Van de Water. 2009-05-25. The neutral kaon mixing parameter B_K from unquenched mixed-action lattice QCD. https://doi.org/10.1103/physrevd.81.014507

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