We present results for the matrix elements of the additional ∆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 ∆MK and K , these constrain the parameters of BSM models. We use improved staggered fermions, with valence 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 ≈ 0.09, 0.06 and 0.045 fm. Valence light-quark masses range down to ≈ m phys s /13 while the light sea-quark masses range down to ≈ m phys s /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, µ = 2 GeV and 3 GeV, and compare them to those obtained by other collaborations. Agreement is found for two of the four BSM B-parameters (B2 and B SUSY 3). The other two (B4 and B5) differ significantly from those obtained using RI-MOM renormalization as an intermediate scheme, but are in agreement with recent preliminary results obtained by the RBC-UKQCD collaboration using RI-SMOM intermediate schemes.

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We present an update on the calculation ofB → D * ν semileptonic form factor at zero recoil using the Oktay-Kronfeld bottom and charm quarks on N f = 2+1+1 flavor HISQ ensembles generated by the MILC collaboration. Preliminary results are given for two ensembles with a ≈ 0.12 and 0.09 fm and M π ≈ 310 MeV. Calculations have been done with a number of valence quark masses, and the dependence of the form factor on them is investigated on the a ≈ 0.12 fm ensemble. The excited state is controlled by using multistate fits to the three-point correlators measured at 4-6 source-sink separations.

We present recent progress in the lattice calculation of leptonic decay constants for B (s) and D (s) mesons using the Oktay-Kronfeld (OK) action for charm and bottom valence quarks, whose masses are tuned non-perturbatively. The calculations are done on 6 HISQ ensembles generated by the MILC collaboration with N f = 2 + 1 + 1 flavors. We also use the HISQ action for the light spectator quarks. Results are presented for the ratios f B s / f B and f D s / f D , which reflect SU(3) flavor symmetry breaking, and are independent of the renormalization constants of the axial currents.

We report recent progress in calculating semileptonic form factors for theB → D * ν andB → D ν decays using the Oktay-Kronfeld (OK) action for bottom and charm quarks. We use the second order in heavy quark effective power counting O(λ 2) improved currents in this work. The HISQ action is used for the light spectator quarks. We analyzed four 2 + 1 + 1-flavor MILC HISQ ensembles with a ≈ 0.09 fm, 0.12 fm and M π ≈ 220 MeV, 310 MeV: a09m220, a09m310, a12m220, a12m310. Preliminary results for B → D * ν decays form factor h A 1 (w) at zero recoil (w = 1) are reported. Preliminary results for B → D ν decays form factors h ± (w) over a kinematic range 1 < w < 1.3 are reported as well.