Electric dipole moment of the rho-meson

TL;DR

This paper calculates the rho-meson's electric dipole moment using Dyson-Schwinger equations, considering various CP-violating operators, providing insights relevant for understanding fundamental symmetry violations in particle physics.

Contribution

It introduces a method to compute the rho-meson EDM from leading CP-violating operators using a symmetry-preserving truncation of QCD's Dyson-Schwinger equations.

Findings

Quark-EDM and -chromo-EDM contributions are comparable in magnitude.

Four-quark operator contributions can be as significant as quark-EDM and -chromo-EDM if theta-term suppression occurs.

The approach serves as a prototype for calculating the neutron's EDM.

Abstract

At an hadronic scale the effect of CP-violating interactions that typically appear in extensions of the Standard Model may be described by an effective Lagrangian, in which the operators are expressed in terms of lepton and partonic gluon and quark fields, and ordered by their mass dimension, k .geq. 4. Using a global-symmetry-preserving truncation of QCD's Dyson-Schwinger equations, we compute the rho-meson's electric dipole moment (EDM), d_rho, as generated by the leading dimension-four and -five CP-violating operators and an example of a dimension-six four-quark operator. The two dimension-five operators; viz., quark-EDM and -chromo-EDM, produce contributions to d_rho whose coefficients are of the same sign and within a factor of two in magnitude. Moreover, should a suppression mechanism be verified for the theta-term in any beyond-Standard-Model theory, the contribution from a four-quark operator can match the quark-EDM and -chromo-EDM in importance. This study serves as a prototype for the more challenging task of computing the neutron's EDM.