Penta-quark in anisotropic lattice QCD

Penta-quark (5Q) baryons are studied using anisotropic lattice QCD for high-precision measurement of temporal correlators. A non-NK-type interpolating field is employed to study the 5Q states with J(P) = 1/2(+/-) and I = 0. In J(P) = 1/2(+) channel, the lowest-lying state is found at m(5Q) similar or equal to 2.25 GeV, which is too massive to be identified as the Theta(+)(1540). In J(P) = 1/2(-) channel, the lowest-lying state is found at m(5Q) similar or equal to 1.75 GeV. To distinguish a compact 5Q resonance state from an NK scattering state, a new method with "hybrid boundary condition (HBC)" is proposed. As a result of the HBC analysis, the observed state in the negative-parity channel turns out to be an NK scattering state.