Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA
; George Washington Univ, Dept Phys, Ctr Nucl Studies, Washington, DC 20052 USA
; Jefferson Lab, Newport News, VA 23606 USA
; Acad Sinica, Inst High Energy Phys, Beijing 100039, Peoples R China
; Univ Adelaide, CSSM, Adelaide, SA 5005, Australia
; Univ Adelaide, Dept Phys, Adelaide, SA 5005, Australia
We present a quenched lattice QCD calculation of spin-1/2 five-quark states with uudd (s) over bar quark content for both positive and negative parities. We do not observe any bound pentaquark state in these channels for either I=0 or I=1. The states we found are consistent with KN scattering states which are checked to exhibit the expected volume dependence of the spectral weight. The results are based on overlap-fermion propagators on two lattices, 12(3)x28 and 16(3)x28, with the same lattice spacing of 0.2 fm, and pion mass as low as similar to180 MeV.