Isospin Breaking Effects on the Lattice

TL;DR

This paper reviews recent lattice QCD+QED methods to calculate isospin breaking effects, which are crucial for precise hadron physics predictions, and discusses recent results on the hadron spectrum.

Contribution

It introduces new lattice simulation techniques for accurately computing isospin breaking effects from first principles, including combined QCD+QED simulations and renormalization methods.

Findings

Isospin breaking effects are at the percent level and significant for current precision.

Recent lattice results quantify isospin breaking impacts on the hadron spectrum.

Methods enable separation of QCD and QED contributions to isospin breaking.

Abstract

Isospin symmetry is not exact and the corrections to the isosymmetric limit are, in general, at the percent level. For gold plated quantities, such as pseudoscalar meson masses or the kaon leptonic and semileptonic decay rates, these effects are of the same order of magnitude of the errors quoted in nowadays lattice calculations and cannot be neglected any longer. In this talk I discuss the methods that have been developed in the last few years to calculate isospin breaking corrections by starting from first principles lattice simulations. In particular, I discuss how to perform a combined QCD+QED lattice simulation and a renormalization prescription to be used in order to separate QCD from QED isospin breaking effects. A brief review of recent lattice results of isospin breaking effects on the hadron spectrum is also included.