Masses of $[\mathbf{70},{\mathrm{\ell }}^{+}]$ Baryons in the $1\mathrm{/}{N}_c$ Expansion

The masses of positive $[\mathbf{70},0^{+}]$ and $[\mathbf{70},2^{+}]$ nonstrange and strange baryons are calculated in the $1\mathrm{/}{N}_c$ expansion. The approach is based on the separation of a system of $N_c$ quarks into an excited core and an excited quark. The previous work for two flavor baryons is now extended to include strange baryons, to first order in SU(3)-flavor breaking. We show that the extension to $N_f=3$ maintains the regularities previously observed in the behaviour of the linear term in $N_c$, of the spin-spin and of the spin-orbit terms. In particular the contribution of the spin-dependent terms decrease with the excitation energy, the dominant term remaining the spin-spin term.