The masses of the negative parity SU(6) 70-plet baryons are analyzed in the 1/N_c expansion to order 1/N_c and to first order in SU(3) breaking. At this level of precision there are twenty predictions. Among them there are the well known Gell-Mann Okubo and equal spacing relations, and four new relations involving SU(3) breaking splittings in different SU(3) multiplets. Although the breaking of SU(6) symmetry occurs at zeroth order in 1/N_c, it turns out to be small. The dominant source of the breaking is the hyperfine interaction which is of order 1/N_c. The spin-orbit interaction, of zeroth order in 1/N_c, is entirely fixed by the splitting between the singlet states A(1405) and A(1520), and the spin-orbit puzzle is resolved by the presence of other zeroth order operators involving flavor exchange.

Authors: Jose Goity, C.L. Schat, N.N. Scoccola

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