Search for the pentaquark resonance signature in lattice QCD
  Claims concerning the possible discovery of the \Theta^+ pentaquark, with minimal quark content uudd\bar{s}, have motivated our comprehensive study into possible pentaquark states using lattice QCD. We review various 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 x 40 lattice in the quenched approximation. The standard lattice resonance signal of increasing attraction between baryon constituents for increasing quark mass is not observed for spin-1/2 pentaquark states. We conclude that evidence supporting the existence of a spin-1/2 pentaquark resonance does not exist in quenched QCD. 
B. G. Lasscock, J. Hedditch, D. B. Leinweber, W. Melnitchouk, A. W.   Thomas, A. G. Williams, R. D. Young, J. M. Zanotti