Search for the S=+1 pentaquarks in quenched lattice QCD

Abstract

We study spin $\frac{1}{2}$ hadronic states in quenched lattice QCD to search for a possible $S=+1$ pentaquark resonance. Our work is the first systematic lattice QCD study which properly carries out the following analyses: {\it (1) the careful extraction of the first two low energy states with very high statistics and the variational method} and {\it (2) the study of volume dependences of eigenenergies and spectral weights to distinguish resonance states from scattering states}. Simulations are carried out on $8^3\times 24$, $10^3\times 24$, $12^3\times 24$ and $16^3\times 24$ lattices at $\beta$=5.7 with the standard plaquette gauge action and the Wilson quark action. Our result indicates the existence of a resonance state lying slightly above the NK threshold in $(I,J^P)=(0,{\frac{1}{2}}^{-})$ channel in quenched QCD.

Talk presented at the 23rd International Symposium on Lattice Field Theory "Lattice2005", Dublin, July 25-30, 2005; uses PoS.cls