Estimate of the quark-gluon coupling strength from baryon masses

The magnetic and color-magnetic spin-spin interactions are used to relate the fine-structure constant $\alpha$ to the corresponding strong-interaction constant ${\alpha }_s$ in terms of measured baryon masses and the nucleon-quark effective mass obtained from nucleon magnetic moments. An expression for the effective mass difference between the $d$ and $u$ quark is also obtained. The method gives ${\alpha }_s=0.65\mathrm{}$ and $d-u=2.8\mathrm{}$ MeV.