A Precision Measurement of the Neutron Scattering Length of He-4 Using Neutron Interferometry

TL;DR

This paper presents a highly precise neutron scattering length measurement for helium-4 using neutron interferometry, significantly improving accuracy and updating the world average, with implications for nuclear physics research.

Contribution

The study provides the most precise measurement to date of the neutron scattering length of helium-4, reducing uncertainty and revising the world average.

Findings

Measured neutron scattering length with 0.08% precision

Revised the world average of the scattering length

Disagrees with previous interferometric measurements

Abstract

We report a 0.08 % measurement of the bound neutron scattering length of $^4$He using neutron interferometry. The result is $b = (3.0982 \pm 0.0021 \mbox{ [stat]} \pm 0.0014 \mbox{ [sys]}) \mbox{ fm}$. The corresponding free atomic scattering length is $a = (2.4746 \pm 0.0017 \mbox{ [stat]} \pm 0.0011 \mbox{ [sys]}) \mbox{ fm}$. With this result the world average becomes $b = (3.0993 \pm 0.0025)$ fm, a 2 % downward shift and a reduction in uncertainty by more than a factor of six. Our result is in disagreement with a previous neutron interferometric measurement but is in good agreement with earlier measurements using neutron transmission.