Consistent quark model with hyperfine interactions for the ground and low-lying excited baryon states

Isgur and Karl have recently analyzed the ground and low-lying excited baryon states; the negative-parity and positive-parity baryons are treated separately using different parameter sets. In this paper we show how the Hamiltonian introduced by Isgur and Karl to examine the positive-parity baryons can be modified to apply to the negative-parity baryons. In particular, the mass difference between $\Lambda {\frac{5}{2}}^{-}$ and $\Sigma {\frac{5}{2}}^{-}$ is restored to a value consistent with experiment.