Excited baryons in lattice QCD

Abstract

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 ${J}^{P}={\frac{1}{2}}^{\ensuremath{-}}$ states with a small mass splitting. The study of different $\ensuremath{\Lambda}$ interpolating fields suggests a similar splitting between the lowest two $\ensuremath{\Lambda}{\frac{1}{2}}^{\ensuremath{-}}$ octet states. However, the empirical mass suppression of the ${\ensuremath{\Lambda}}^{*}(1405)$ is not evident in these quenched QCD simulations, suggesting a potentially important role for the meson cloud of the ${\ensuremath{\Lambda}}^{*}(1405)$ and/or a need for more exotic interpolating fields.