As part of a larger project to estimate the fB decay constant, we are recalculating fB_static using a variational smearing method in an effort to improve accuracy. Preliminary results for the static B_B parameter and HQET two point functions are also presented.
Calculations of pseudoscalar decay constants of B, Bs, K and pi mesons with physical light quarks are presented. We use HISQ ensembles that include u,d,s and c sea quarks at three lattice spacings. HISQ is used for the valence light quarks and a radi
atively improved NRQCD action for the heavy quarks. The key results are f_{B^+}=0.184(4)$ GeV, f_{B_s}=0.224(4) GeV, f_{B_s}/f_{B^+}=1.217(8), f_{K^+}/f_{pi^+}=1.1916(21), f_{K^+}=155.37(34) MeV, giving a significant improvement over previous results that required chiral extrapolation. We also calculate the Wilson flow scale w_0, finding w_0=0.1715(9) fm.
We present a stochastic method for the calculation of baryon three-point functions that is more versatile compared to the typically used sequential method. We analyze the scaling of the error of the stochastically evaluated three-point function with
the lattice volume and find a favorable signal-to-noise ratio suggesting that our stochastic method can be used efficiently at large volumes to compute hadronic matrix elements.
We report on the nucleon decay matrix elements with domain-wall fermions in quenched approximation. Results from direct and indirect method are compared with a focus on the process of a proton decaying to a pion and a lepton. We discuss the renormali
zation necessary for the matching to the continuum theory. Preliminary results for the renormalized chiral lagrangian parameters are presented.
We present our results for the on-shell Delta I = 3/2 kaon decay matrix elements using domain wall fermions and the DBW2 gauge action at one coarse lattice spacing corresponding to 1/a = 1.31 GeV in the quenched approximation. The on-shell matrix ele
ments are evaluated in two different frames: the center-of-mass frame and non-zero total-momentum frame. We employ the formula proposed by Lellouch and Luscher in the center-of-mass frame, and its extension for non-zero total momentum frame to extract the infinite volume, on-shell, center-of-mass frame decay amplitudes. We determine the decay amplitude at the physical pion mass and momentum from the chiral extrapolation and an interpolation of the relative momentum using the results calculated in the two frames. We have obtained Re(A_2) = 1.66(23)(^{+48}_{-03})(^{+53}_{-0}) x 10^{-8} GeV and Im(A_2) = -1.181(26)(^{+141}_{-014})(^{+44}_{-0}) x 10^{-12} GeV at the physical point, using the data at the relatively large pion mass, m_pi > 0.35 GeV. The first error is statistic, and the second and third are systematic. The second error is estimated with several fits of the chiral extrapolation including (quenched) chiral perturbation formula at next to leading order using only lighter pion masses. The third one is estimated with an analysis using the lattice dispersion relation. The result of Re(A_2) is reasonably consistent with experiment.