Test experiment to search for a neutron EDM by the Laue diffraction method

TL;DR

This paper reports a prototype experiment using Laue diffraction to measure the neutron electric dipole moment, assessing statistical sensitivity and systematic effects, and proposing improvements for future measurements.

Contribution

It introduces a novel Laue diffraction method for nEDM measurement and analyzes systematic effects related to crystal deformation and spin rotation.

Findings

Statistical sensitivity of about 6×10⁻²⁴ e·cm per day.

Systematic effects limited by magnetic field homogeneity and a new spin rotation effect.

Potential for an order of magnitude improvement in full-scale setup.

Abstract

A prototype experiment to measure the neutron electric dipole moment (nEDM) by spin-rotation in a non-centrosymmetric crystal in Laue geometry was carried out in order to investigate the statistical sensitivity and systematic effects of the method. The statistical sensitivity to the nEDM was about $6\cdot 10^{-24}$ e$\cdot $cm per day and can be improved by one order of magnitude for the full scale setup. Systematics was limited by the homogeneity of the magnetic field in the crystal region and by a new kind of spin rotation effect. We attribute this effect to a difference of the two Bloch waves amplitudes in the crystal, which is caused by the presence of a small crystal deformation due to a temperature gradient. In a revised scheme of the experiment, this effect could be exploited for a purposeful manipulation of the Bloch waves.