Electric Dipole Moments and Polarizability in the Quark-Diquark Model of the Neutron

TL;DR

This paper discusses the theoretical constraints on the neutron's electric dipole moment within a quark-diquark model, contrasting it with water molecule dipole moments and exploring implications for neutron structure.

Contribution

It introduces a quark-diquark model to reconcile the neutron's electric dipole moment with parity symmetry constraints.

Findings

Neutron's mean electric dipole moment must be zero under parity symmetry.

Water molecule's nonzero dipole moment is consistent with its structure.

Quark-diquark model aligns neutron dipole moment with experimental observations.

Abstract

For a bound state internal wave function respecting parity symmetry, it can be rigorously argued that the mean electric dipole moment must be strictly zero. Thus, both the neutron, viewed as a bound state of three quarks, and the water molecule, viewed as a bound state of ten electrons two protons and an oxygen nucleus, both have zero mean electric dipole moments. Yet, the water molecule is said to have a nonzero dipole moment strength $d=e\Lambda $ with $\Lambda_{H_2O} \approx 0.385\ \dot{A}$. The neutron may also be said to have an electric dipole moment strength with $\Lambda_{neutron} \approx 0.612\ fm$. The neutron analysis can be made experimentally consistent, if one employs a quark-diquark model of neutron structure.