Baryon magnetic moments in large-$N_c$ chiral perturbation theory

The baryon magnetic and transition magnetic moments are computed in heavy baryon chiral perturbation theory in the large-$N_c$ limit, where $N_c$ is the number of colors. One-loop nonanalytic corrections of orders $m_q^{1/2}$ and $m_q\ln m_q$ are incorporated into the analysis, where contributions of both intermediate octet and decuplet baryon states are explicitly included. Expressions are obtained in the limit of vanishing baryon mass differences and compared with the current experimental data. Furthermore, a comparison with conventional heavy baryon chiral perturbation theory is carried out for three light quarks flavors and at the physical value $N_c=3$.

Figure 1

Feynman diagrams which yield nonanalytic $m_q^{1/2}$ corrections to baryon magnetic moments. Dashed lines denote mesons and single and double solid lines denote octet and decuplet baryons, respectively.

Figure 2

Feynman diagrams which yield nonanalytic $m_q\ln m_q$ corrections to the magnetic moments of octet baryons. Dashed lines denote mesons, and single and double solid lines denote octet and decuplet baryons, respectively. Although the wave function renormalization graphs are omitted in the figure for simplicity, they are nevertheless taken into account in the analysis. For decuplet baryons and decuplet-octet transitions the diagrams are similar.