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

## TL;DR

This study examines how tree-level and mean-field improvements affect the light-hadron spectrum in quenched QCD, showing significant mass differences with different clover coefficients and minimal volume effects.

## Contribution

It compares the impact of classical and tadpole-improved clover coefficients on hadron masses in quenched QCD using the SW fermion action.

## Key findings

- Changing the clover coefficient significantly affects certain hadron masses.
- Some quantities like m_V^2 - m_PS^2 remain largely unaffected by improvement choices.
- Lattice volume changes have minimal impact on meson and baryon masses.

## Abstract

We compute the light hadron mass spectrum at beta=5.7 using the O(a) improved Sheikholeslami-Wohlert (SW) 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 Delta, and also in the Edinburgh plot. A number of other quantities, for example m_V^2-m_PS^2, J, am_K/am_\rho and am_{K^*}/am_\rho do not appear to change significantly. We also investigate the effect of changing the lattice volume from approximately (2 fm)^3 to (2.6 fm)^3. We find that the meson masses are consistent to within one standard deviation and baryon masses are consistent to within two standard deviations.