We present the first results for the masses of positive and negative parity excited baryons calculated in lattice QCD using an ${O(a}^2)$-improved gluon action and a fat-link irrelevant clover (FLIC) fermion action in which only the irrelevant operators are constructed with APE-smeared links. The results are in agreement with earlier calculations of $N^{*}$ resonances using improved actions and exhibit a clear mass splitting between the nucleon and its chiral partner. A correlation matrix analysis reveals two low-lying $J^P={\frac{1}{2}}^{-}$ states with a small mass splitting. The study of different $\Lambda$ interpolating fields suggests a similar splitting between the lowest two $\Lambda {\frac{1}{2}}^{-}$ octet states. However, the empirical mass suppression of the ${\Lambda }^{*}\mathrm{}\left(1405\right)\mathrm{}$ is not evident in these quenched QCD simulations, suggesting a potentially important role for the meson cloud of the ${\Lambda }^{*}\mathrm{}\left(1405\right)\mathrm{}$ and/or a need for more exotic interpolating fields.

• Received 26 February 2002

DOI:https://doi.org/10.1103/PhysRevD.67.114506