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Pentaquark baryon in anisotropic lattice QCD
Pentaquark baryon in anisotropic lattice QCD
Ishii, N.
14302
Doi, T.
14303
Iida, H.
14304
Oka, M.
14305
Okiharu, F.
14306
Suganuma, H.
14307
Okiharu, Fumiko
興治, 文子
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.
journal article
American Physical Society
2005-02
application/pdf
Physical Review D
034001
71
1
11
Physical Review D
AA00773624
15507998
https://niigata-u.repo.nii.ac.jp/record/2327/files/034001.pdf
eng
info:doi/10.1103/PhysRevD.71.034001
Copyright: The American Physical Society