Dipole-dipole dispersion interactions between neutrons

TL;DR

This paper analyzes long-range dipole-dipole interactions between neutrons using recent polarizability data, comparing neutron-neutron and neutron-proton collisions, and discusses implications for ultracold neutron confinement.

Contribution

It provides a quantitative analysis of neutron-neutron interactions incorporating dynamical effects and resonance contributions, which was not thoroughly explored before.

Findings

Dynamical effects are significant for distances 50 fm to 1000 fm.

Interactions reach asymptotic limits beyond 1000 fm.

Results have implications for ultracold neutron confinement.

Abstract

We investigate the long-range interactions between two neutrons utilizing recent data on the neutron static and dynamic electric and magnetic dipole polarizabilities. The resulting long-range potentials are used to make quantitative comparisons between the collisions of a neutron with a neutron and a neutron with a proton. We also assess the importance of the first pion production threshold and first excited state of the nucleon, the $\Delta$-resonance ($J^{\pi}$ = + 3/2, I = 3/2). We found both dynamical effects to be quite relevant for distances r between ~ 50 fm up to ~$10^3$ fm in the nn system, the neutron-wall system and in the wall-neutron-wall system, reaching the expected asymptotic limit beyond that. Relevance of our findings to the confinement of ultra cold neutrons inside bottles is discussed.