Kaon Mixing Beyond the SM from Nf=2 tmQCD and model independent constraints from the UTA

TL;DR

This paper provides the first unquenched lattice QCD results for kaon oscillation matrix elements in BSM scenarios, refining constraints on new physics through improved unitarity triangle analysis.

Contribution

It introduces a non-perturbative lattice QCD calculation of  operators relevant for kaon mixing beyond the Standard Model, with continuum limit and physical quark masses.

Findings

Refined bounds on New Physics from improved matrix element calculations.

First unquenched, continuum limit lattice results for  operators.

Enhanced unitarity triangle analysis using new lattice data.

Abstract

We present the first unquenched, continuum limit, lattice QCD results for the matrix elements of the operators describing neutral kaon oscillations in extensions of the Standard Model. Owing to the accuracy of our calculation on \Delta S=2 weak Hamiltonian matrix elements, we are able to provide a refined Unitarity Triangle analysis improving the bounds coming from model independent constraints on New Physics. In our non-perturbative computation we use a combination of Nf=2 maximally twisted sea quarks and Osterwalder-Seiler valence quarks in order to achieve both O(a)-improvement and continuum-like renormalization properties for the relevant four-fermion operators. The calculation of the renormalization constants has been performed non-perturbatively in the RI-MOM scheme. Based on simulations at four values of the lattice spacing and a number of quark masses we have extrapolated/interpolated our results to the continuum limit and physical light/strange quark masses.