The Theta Term in QCD Sum Rules and the Electric Dipole Moment of the Vector Meson

TL;DR

This paper applies QCD sum rules to compute the rho meson's electric dipole moment induced by the vacuum theta-angle, achieving ~30% precision and linking it to the vacuum's topological susceptibility.

Contribution

It introduces a novel application of QCD sum rules to CP-odd observables, specifically calculating the rho meson's EDM related to the theta-term.

Findings

Electric dipole moment of the rho meson calculated with ~30% accuracy.

Explicit relation established between the EDM and vacuum topological susceptibility.

Demonstrates the effectiveness of QCD sum rules for CP-odd electromagnetic observables.

Abstract

We demonstrate that the QCD sum rule method can be successfully applied to the calculation of CP-odd electromagnetic observables induced by a vacuum theta--angle. We implement the approach in calculating the electric dipole moment of the rho meson to ~30% precision, and find that the result can also be explicitly related to the vacuum topological susceptibility.