Speaker
Description
We present the strategy for non-perturbative renormalization of $K\to\pi\pi$ decay matrix elements in the next continuum limit calculation of direct CP violation parameter $\varepsilon'$ using the RBC/UKQCD collaboration's 2+1 flavor physical point Iwasaki ensembles, with inverse lattice spacings 1.73 GeV (48I) and 2.36 GeV (64I). The new NPR program relies on ten ensembles with half of the lattice spacing of 48I, and eight with half of the lattice spacing of 64I, with the final goal being the computation of the continuum limit of the step scaling function to produce the Z-factor matrix at a much higher scale than allowed by discretization errors on the physical point ensembles. Along with 3-flavor SU(3) symmetric ensembles for both lattice spacings, we include 3+1 flavor ensembles with the same lattice spacing. We also add ensembles that vary the mass of the dynamical light, strange, and charm quark to investigate mass dependence, and one additional 3-flavor ensemble with a fixed global topology. Further, we present progress on the development of GPU accelerated All-to-all correlation functions, and present the speed gained in the various kernels for the calculation of the $K\to\pi\pi$ correlation functions on the 64I ensemble.