Neutral kaon mixing beyond the standard model withnf=2+1chiral fermions

Abstract

We compute the hadronic matrix elements of the four-quark operators needed for the study of ${K}^{0}\ensuremath{-}{\overline{K}}^{0}$ mixing beyond the Standard Model (SM). We use ${n}_{f}=2+1$ flavors of domain-wall fermion that exhibit good chiral-flavor symmetry. The renormalization is performed nonperturbatively through the RI-MOM scheme and our results are converted perturbatively to $\overline{\mathrm{MS}}$. The computation is performed on a single lattice spacing $a\ensuremath{\sim}0.086$ with a lightest unitary pion mass of 290 MeV. The various systematic errors, including the discretization effects, are estimated and discussed. Our results confirm a previous quenched study, where large ratios of non-SM to SM matrix elements were obtained.