Effect of tree-level and mean-field improvement on the light-hadron spectrum in quenched QCD

Abstract

We compute the light-hadron mass spectrum at $\ensuremath{\beta}=5.7$ using the $O(a)$-improved Sheikholeslami-Wohlert fermion action with two choices of the clover coefficient: the classical value $c=1$ and a mean-field or tadpole-improved estimate $c=1.57$. We compare our results with those of the GF11 Collaboration who use the Wilson fermion action $(c=0)$. We find that changing $c$ from zero to 1 and 1.57 leads to significant differences in the masses of the chirally extrapolated and strange pseudoscalar and vector mesons, the nucleon, the $\ensuremath{\Delta}$, and also in the Edinburgh plot. A number of other quantities, for example, ${m}_{V}^{2}\ensuremath{-}{m}_{P}^{2}, J, {\mathrm{am}}_{K}{/am}_{\ensuremath{\rho}},$ and ${\mathrm{am}}_{{K}^{*}}{/am}_{\ensuremath{\rho}}$ do not appear to change significantly. We also investigate the effect of changing the lattice volume from approximately (2 ${\mathrm{f}\mathrm{m})}^{3}$ to (2.6 ${\mathrm{f}\mathrm{m})}^{3}$. We find that the meson masses are consistent to within one standard deviation and baryon masses are consistent to within two standard deviations.