Lattice QCD Studies of Pentaquarks and Exotics

The possible discovery of the Θ+ pentaquark has motivated a number of studies into its nature using lattice QCD. Initial studies focused on spin-1/2 states and more recently also spin-3/2 states. Here we report the results of the first exploratory study in quenched lattice QCD of pentaquarks with both spin-1/2 and spin-3/2 using the FLIC fermion action. We do not find any evidence for the standard lattice resonance signature of attraction (i.e. binding at quark masses near the physical regime) in the spin-1/2 channels or in the JP=3/2− channel. Some evidence of binding is inferred in the isoscalar 3/2+ channel. We also present the results of our study into exotic meson states using hybrid meson interpolators with explicit gluonic degrees of freedom. We find a candidate for the JPC=1−+ exotic meson which has a mass consistent with the π1(1600) experimental candidate.