Baryon electric dipole moments from strong CP violation

TL;DR

This paper calculates baryon electric dipole moments using chiral perturbation theory and lattice QCD data, revealing dependencies on low-energy constants and providing precise estimates relevant for understanding CP violation.

Contribution

It provides the first next-to-leading order calculations of baryon EDMs in chiral perturbation theory and relates them to lattice QCD data, including finite volume corrections.

Findings

Baryon EDMs depend on two combinations of low-energy constants.

Lattice QCD data yields neutron EDM d_n = -2.9±0.9 and proton EDM d_p = 1.1±1.1 in 10^{-16} e θ_0 cm.

Next-to-leading order terms are essential for precise lattice QCD extraction.

Abstract

The electric dipole form factors and moments of the ground state baryons are calculated in chiral perturbation theory at next-to-leading order. We show that the baryon electric dipole form factors at this order depend only on two combinations of low-energy constants. We also derive various relations that are free of unknown low-energy constants. We use recent lattice QCD data to calculate all baryon EDMs. In particular, we find d_n = -2.9\pm 0.9 and d_p = 1.1\pm 1.1 in units of 10^{-16} e \theta_0 cm. Finite volume corrections to the moments are also worked out. We show that for a precision extraction from lattice QCD data, the next-to-leading order terms have to be accounted for.