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

Abstract

It has been shown recently that a neutron placed in an external quasistatic electric field develops an induced electric dipole moment p_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 p_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 1 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.