Search for the pentaquark resonance signature in lattice QCD

Abstract

Claims concerning the possible discovery of the ${\ensuremath{\Theta}}^{+}$ pentaquark, with minimal quark content $uudd\overline{s}$, have motivated our comprehensive study into possible pentaquark states using lattice QCD. We review various spin-$\frac{1}{2}$ pentaquark interpolating fields in the literature and create a new candidate ideal for lattice QCD simulations. Using these interpolating fields we attempt to isolate a signal for a five-quark resonance. Calculations are performed using improved actions on a large ${20}^{3}\ifmmode\times\else\texttimes\fi{}40$ lattice in the quenched approximation. The standard lattice resonance signal of binding at quark masses near the physical regime, observed for established baryon resonances, is not observed for spin-$\frac{1}{2}$ pentaquark states. Thus we find no evidence supporting the existence of a spin-$\frac{1}{2}$ pentaquark resonance in quenched QCD.