Dressed-Quark Anomalous Magnetic Moments

Perturbation theory predicts that a massless fermion cannot possess a measurable magnetic moment. We explain, however, that the nonperturbative phenomenon of dynamical chiral symmetry breaking generates a momentum-dependent anomalous chromomagnetic moment for dressed light quarks, which is large at infrared momenta, and demonstrate that consequently these same quarks also possess an anomalous electromagnetic moment with similar magnitude and opposite sign.

Figure 1

Upper panel: $f_{\gamma }$ (${\mathrm{GeV}}^{-1}$) in Eq. (25) cf. $\eta {\Delta }_B(p^2,p^2)$, both computed using Eqs. (15, 17). Lower panel: Anomalous chromo- and electromagnetic moment distributions for a dressed quark, computed using Eq. (26). The dashed curve in both panels is the rainbow-ladder (RL) truncation result.