Lattice QCD calculation of strong isospin breaking effects

TL;DR

This paper introduces a new lattice QCD method to precisely evaluate isospin breaking effects caused by up-down quark mass differences, applicable to various hadronic observables.

Contribution

The paper proposes a novel approach based on path-integral expansion in powers of quark mass differences for high-precision isospin breaking calculations.

Findings

Method successfully applied to kaon masses and decay constants

Accurate computation of neutron-proton mass splitting

Applicable to a wide range of hadronic observables

Abstract

We present a new method to evaluate with high precision the isospin breaking effects due to the mass difference between the up and down quarks using lattice QCD. Our proposal is applicable in principle to any hadronic observable which can be computed on the lattice. It is based on the expansion of the path-integral in powers of the small parameter $m_d - m_u$. In this talk we discuss how to apply this method to compute the leading isospin breaking effects for several physical quantities of interest: the kaon masses, the kaon decay constants and the neutron-proton mass splitting.