Beyond the Standard Model corrections to $K^0-\bar{K}^0$ mixing

TL;DR

This paper computes B-parameters for BSM operators affecting $K^0-ar{K}^0$ mixing using lattice QCD with improved staggered fermions across multiple lattice spacings, providing essential inputs for new physics models.

Contribution

It presents the first lattice QCD calculation of B-parameters for BSM operators relevant to kaon mixing using HYP-smeared staggered fermions on multiple lattice spacings.

Findings

Preliminary B-parameter results at three lattice spacings.

Use of SU(2) staggered chiral perturbation theory for extrapolation.

Results include only statistical errors.

Abstract

We calculate the B-parameters for operators arising in theories of new physics beyond the standard model (BSM) using HYP-smeared improved staggered fermions on the MILC asqtad lattices with N_f = 2+1 flavors. We use three different lattice spacings (a ~ 0.045, 0.06 and 0.09 fm) at a fixed ratio of light to strange quarks, m_l/m_s = 1/5, to obtain the continuum results. Operator matching is done using perturbative matching at one-loop order, and results are run to 2 or 3 GeV using two-loop running in the MS-bar scheme. For the chiral and continuum extrapolations, we use SU(2) staggered chiral perturbation theory. We present preliminary results with only statistical errors.