Kaon Bsm B-Parameters Using Improved Staggered Fermions From N-F=2+1 Unquenched Qcd

We present results for the matrix elements of the additional Delta S = 2 operators that appear in models of physics beyond the Standard Model (BSM), expressed in terms of four BSM B-parameters. Combined with experimental results for Delta M-K and epsilon(K), these constrain the parameters of BSM models. We use improved staggered fermions, with valence hypercubic blocking transfromation (HYP)-smeared quarks and N-f = 2 + 1 flavors of "asqtad" sea quarks. The configurations have been generated by the MILC Collaboration. The matching between lattice and continuum four-fermion operators and bilinears is done perturbatively at one-loop order. We use three lattice spacings for the continuum extrapolation: a approximate to 0.09, 0.06 and 0.045 fm. Valence light-quark masses range down to approximate to m(s)(phys)/13 while the light sea-quark masses range down to approximate to m(s)(phys)/20. Compared to our previous published work, we have added four additional lattice ensembles, leading to better controlled extrapolations in the lattice spacing and sea-quark masses. We report final results for two renormalization scales, mu = 2 and 3 GeV, and compare them to those obtained by other collaborations. Agreement is found for two of the four BSM B-parameters (B-2 and B-3(SUSY)). The other two (B-4 and B-5) differ significantly from those obtained using regularization independent momentum subtraction (RI-MOM) renormalization as an intermediate scheme, but are in agreement with recent preliminary results obtained by the RBC-UKQCD Collaboration using regularization independent symmetric momentum subtraction (RI-SMOM) intermediate schemes.