@article{oai:niigata-u.repo.nii.ac.jp:00002327,
 author = {Ishii, N. and Doi, T. and Iida, H. and Oka, M. and Okiharu, F. and Suganuma, H.},
 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 a_s/a_t = 4 for a high-precision mass measurement. The standard Wilson action at β= 5.75 and the O (a) improved Wilson quark action with k = 0.1210(0.0010)0.1240 are employed on a 12^3 × 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, m_<5Q> = 2.25 GeV, which is much heavier than the experimentally observed Θ^+ (1540). The lowest negative-parity 5Q state appears at m_<5Q> = 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}
}