New estimation for neutron-neutron scattering length: charge symmetry and charge independence breaking revisited

TL;DR

This paper reanalyzes neutron-neutron scattering length measurements, emphasizing the role of three-nucleon forces and pion exchange differences, leading to a refined estimate of the scattering length.

Contribution

It provides a new estimation method for neutron-neutron scattering length that isolates two-body effects from three-body force contributions.

Findings

The limiting value of $a_{nn}=-15.8\,fm$ is free of three-body force effects.

Differences between $a_{nn}$ and $a_{np}$ can be explained by one-pion exchange potential variations.

The analysis refines understanding of charge symmetry and independence breaking in nuclear forces.

Abstract

Recent experimental results for neutron-neutron scattering length are reanalyzed from the point of view of three-nucleon force contribution. We found that the limiting value of $a_{nn}=- 15.8\pm 0.5$~fm must be free of any implicit three-body force contribution. We have also shown that the difference between the above experimental value of $a_{nn}$ and the well established value of neutron-proton scattering length $a_{np}$ can be explained by differences in the one-pion exchange potentials.