Weak Matrix Elements of Beyond the Standard Model $\Delta s=2$ four-quark operators from nf=2+1 Domain-Wall fermions

TL;DR

This study computes hadronic matrix elements of four-quark operators relevant for $K^0-{ar K^0}$ mixing beyond the Standard Model using nf=2+1 Domain-Wall fermions, confirming large ratios of non-SM to SM matrix elements.

Contribution

First non-perturbative calculation of these matrix elements with nf=2+1 Domain-Wall fermions at a single lattice spacing, including systematic error estimates.

Findings

Large ratios of non-SM to SM matrix elements confirmed.

Results consistent with previous quenched studies.

Systematic errors carefully estimated.

Abstract

We report on our computation of the hadronic matrix elements of the four-quark operators needed for the study of $K^0-{\bar K^0}$ mixing beyond the Standard Model (SM). We consider nf=2+1 Domain-Wall fermions on Iwasaki gauge action with lightest unitary pion of 290 MeV and a single lattice spacing a=0.086 fm. The renormalization is performed non-perturbatively through the RI-MOM scheme and our results are converted perturbatively to MSbar. We have estimated the various systematic errors. Our results confirm a previous quenched study, where large ratios of non-SM to SM matrix elements were obtained.