@article{oai:niigata-u.repo.nii.ac.jp:00002328,
 author = {Ishii, N. and Doi, T. and Iida, H. and Okiharu, F.},
 issue = {034001},
 journal = {Physical Review D, Physical Review D},
 month = {Feb},
 note = {The pentaquark (5Q) baryon is studied in anisotropic quenched lattice QCD with renormalized anisotropy as/at=4 for a high-precision mass measurement. The standard Wilson action at β=5.75 and the O(a) improved Wilson quark action with κ=0.1210(0.0010)0.1240 are employed on a 123×96 lattice. Contribution of excited states is suppressed by using a smeared source. We investigate both the positive- and negative-parity 5Q baryons with I=0 and spin J=1/2 using a non-NK-type interpolating field. After chiral extrapolation, the lowest positive-parity state is found to have a mass, m5Q=2.25  GeV, which is much heavier than the experimentally observed Θ+(1540). The lowest negative-parity 5Q state appears at m5Q=1.75  GeV, which is near the s-wave NK threshold. To distinguish spatially-localized 5Q resonances from NK-scattering states, we propose a new general method imposing a “Hybrid Boundary Condition (HBC),” where the NK threshold is artificially raised without affecting compact five-quark states. The study using the HBC method shows that the negative-parity state observed on the lattice is not a compact 5Q state but an s-wave NK-scattering state.},
 pages = {1--11},
 title = {Pentaquark baryon in anisotropic lattice QCD},
 volume = {71},
 year = {2005}
}