High energy neutron scattering from hydrogen using a direct geometry spectrometer

TL;DR

This study measures the hydrogen atom's neutron scattering cross section using a direct geometry spectrometer across a broad energy range, finding results consistent with conventional theory and challenging recent quantum entanglement-based explanations.

Contribution

It provides the first broad-range direct geometry measurements of hydrogen's neutron cross section, showing no momentum dependence and supporting conventional scattering theory.

Findings

Hydrogen cross section measured as 80 +/- 4 barns.

No observed momentum dependence in the cross section.

Demonstrates the capability of direct geometry spectrometers at high energies.

Abstract

Deep inelastic neutron scattering experiments using indirect time-of-flight spectrometers have reported a smaller cross section for the hydrogen atom than expected from conventional scattering theory. Typically, at large momentum transfers, a deficit of 20-40% in the neutron scattering intensity has been measured and several theories have been developed to explain these results. We present a different approach to this problem by investigating the hydrogen cross section in polyethylene using the direct geometry time-of-flight spectrometer MARI with the incident energy fixed at a series of values ranging from Ei=0.5 eV to 100 eV. These measurements span a much broader range in momentum than previous studies and with varying energy resolutions. We observe no momentum dependence to the cross section with an error of 4% and through a comparison with the scattering from metal foil standards measure the absolute bound cross section of the hydrogen atom to be sigma(H)= 80 +/- 4 barns. These results are in agreement with conventional scattering theory but contrast with theories invoking quantum entanglement and neutron experiments supporting them. Our results also illustrate a unique use of direct geometry chopper instruments at high incident energies and demonstrate their capability for conducting high-energy spectroscopy.