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 JP=1/2± and I=0. In JP=1/2+ channel, the lowest-lying state is found at m5Q≃2.25 GeV, which is too massive to be identified as the Θ+(1540). In JP=1/2− channel, the lowest-lying state is found at m5Q≃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.