Observability of an induced electric dipole moment of the neutron from nonlinear QED

TL;DR

This paper proposes an experiment to detect an induced electric dipole moment in neutrons caused by nonlinear QED effects, which could reveal quantum vacuum fluctuations through measurable scattering asymmetries.

Contribution

It introduces a feasible experimental method to observe neutron induced dipole moments from nonlinear QED, linking quantum vacuum effects to measurable neutron scattering asymmetries.

Findings

Asymmetry in polarized neutron scattering can reach 10^{-3} for epithermal neutrons.

Expected effects are within experimental detection limits for thermal neutrons.

Observation would confirm nonlinear electrodynamics effects due to quantum fluctuations.

Abstract

It has been shown recently that a neutron placed in an external quasistatic electric field develops an induced electric dipole moment $\mathbf{p}_{\mathrm{IND}}$ due to quantum fluctuations in the QED vacuum. A feasible experiment which could detect such an effect is proposed and described here. It is shown that the peculiar angular dependence of $\mathbf{p}_{\mathrm{IND}}$ on the orientation of the neutron spin leads to a characteristic asymmetry in polarized neutron scattering by heavy nuclei. This asymmetry can be of the order of $10^{-3}$ for neutrons with epithermal energies. For thermalized neutrons from a hot moderator one still expects experimentally accessible values of the order of $10^{-4}$. The contribution of the induced effect to the neutron scattering length is expected to be only one order of magnitude smaller than that due to the neutron polarizability from its quark substructure. The experimental observation of this scattering asymmetry would be the first ever signal of nonlinearity in electrodynamics due to quantum fluctuations in the QED vacuum.