Magnetic moments of light nuclei from lattice quantum chromodynamics

TL;DR

This study uses lattice QCD to calculate magnetic moments of light nuclei at heavy quark masses, showing structural similarities to real nuclei and supporting shell-model descriptions.

Contribution

First lattice QCD calculations of light nuclei magnetic moments at unphysical quark masses, revealing structural features consistent with experimental observations.

Findings

Magnetic moments of ${}^3$He and triton resemble shell-model predictions.

Deuteron magnetic moment matches nucleon isoscalar moment.

Nuclear structure at heavy quark masses resembles that at physical masses.

Abstract

We present the results of lattice QCD calculations of the magnetic moments of the lightest nuclei, the deuteron, the triton and ${}^3$He, along with those of the neutron and proton. These calculations, performed at quark masses corresponding to $m_\pi \sim 800$ MeV, reveal that the structure of these nuclei at unphysically heavy quark masses closely resembles that at the physical quark masses. In particular, we find that the magnetic moment of ${}^3$He differs only slightly from that of a free neutron, as is the case in nature, indicating that the shell-model configuration of two spin-paired protons and a valence neutron captures its dominant structure. Similarly a shell-model-like moment is found for the triton, $\mu_{{}^3{\rm H}} \sim \mu_p$. The deuteron magnetic moment is found to be equal to the nucleon isoscalar moment within the uncertainties of the calculations.