Light quark masses

TL;DR

This paper reviews the current understanding of light quark masses, emphasizing the importance of lattice and effective field theory methods in low energy QCD, and discusses unresolved issues affecting precision determinations.

Contribution

It summarizes recent progress and challenges in determining light quark masses using lattice QCD and effective theories, highlighting areas needing further research.

Findings

Current lattice methods provide precise quark mass ratios.

Electromagnetic self-energies significantly impact mass determinations.

Unresolved issues remain in accurately extracting light quark masses.

Abstract

Low energy precision experiments provide significant tests of the laws of nature that can reveal physics beyond the Standard Model. A good theoretical understanding of the low energy properties of QCD is required for this purpose. The recent developments at the interface between lattice and effective field theory methods provide an excellent basis for pion physics already now, while the extension required to explore the low energy properties in the strange quark sector yet calls for further work, also in view of a better determination of the light quark masses. At the precision achieved in lattice determination of quark mass ratios, the e.m. self-energies of the mesons play an important role. I point out some unresolved issues occurring in this context and then summarize the present knowledge of the light quark masses.