Finite Size Effect in Excited Baryon Spectroscopy

We investigate the finite size effect on masses of excited baryons in quenched lattice QCD simulation. For this purpose, we perform numerical simulations at three different lattice sizes, La\simeq 1.6, 2.2 and 3.2 fm. The gauge configurations are generated with the single plaquette gauge action at \beta=6/g^2=6.2, and the quark propagator are computed with the Wilson fermion action. To access to two parity states of the nucleon and four different spin-parity states of the \Delta baryon, the appropriate spin/parity projection are carried out. We find that the spatial lattice size is required to be as large as 3 fm to remove the finite size effect on excited baryons even in the heavy quark region (M_\pi/M_\rho\simeq 0.82, 0.87), where that on the nucleon is negligible. On our largest lattice (La\simeq 3.2 fm), all mass spectra of the J^P=1/2^\pm nucleons and the J^P=1/2^\pm, 3/2^\pm \Delta baryons are roughly consistent with experimental values after naive chiral extrapolation.