N. Ishii, T. Doi, H. Iida, M. Oka, F. Okiharu, H. Suganuma, K. Tsumura
Abstract
Anisotropic lattice QCD studies of penta-quarks(5Q) with J^P=1/2^± and 3/2^± are presented at the quenched level together with tetra-quarks(4Q). The standard gauge action at β=5.75 and O(a) improved quark (clover) action with κ=0.1410(0.010)0.1440 are employed on the anisotropic lattice with the renormalized anisotropy a_s/a_t = 4. The ``hybrid boundary condition(HBC)'' is adopted to discriminate a compact resonance state from scattering states. Only massive 5Q states are found for J^P=1/2^+ and 3/2^±, which cannot be identified as Θ^+(1540). A low-lying 5Q state is found for J^P=1/2^- at m₅Q≃ 1.75 GeV, which however turns out to be an NK scattering state through the HBC analysis. A preliminary result for 4Q states is presented suggesting an existence of a compact 4Q resonance at m₄Q ≃ 1.1 GeV in the idealized SU(4)_f chiral limit.