Note on the magnetic moment of the nucleon

TL;DR

This paper uses the Goldberger-Treiman relation to estimate constituent quark masses and calculates the proton and neutron magnetic moments, analyzing deviations from experimental values and discussing their origins.

Contribution

It provides a theoretical calculation of nucleon magnetic moments based on the Goldberger-Treiman relation and discusses the deviations from experimental data.

Findings

Calculated proton magnetic moment: 2.850±0.009

Calculated neutron magnetic moment: -1.889±0.006

Deviations from experimental data are 2.0% and 1.3%

Abstract

The Goldberger-Treiman relation $M=2\pi/\sqrt{3}f^{\rm cl}_\pi$ where $M$ is the constituent quark mass in the chiral limit (cl) and $f^{\rm cl}_\pi$ the pion decay constant in the chiral limit predicts constituent quark masses of $m_u=328.8\pm 1.1$ MeV and $m_d=332.3\pm 1.1$ MeV for the up and down quark, respectively, when $f^{\rm cl}_\pi=89.8\pm 0.3$ MeV is adopted. Treating the constituent quarks as bare Dirac particles the following zero order values $\mu^{(0)}}_p=2.850\pm 0.009$ and $\mu^{(0)}}_n= -1.889\pm 0.006$ are obtained for the proton and neutron magnetic moments, leading to deviations from the experimental data of 2.0% and 1.3%, respectively. These unavoidable deviations are discussed in terms of contributions to the magnetic moments proposed in previous work.