The Light Hadron Spectrum and Decay Constants in Quenched Lattice QCD

We present results for light hadrons composed of both degenerate and non-degenerate quarks in quenched lattice QCD. We calculate masses and decay constants using 60 gauge configurations with an $O(a)$–improved fermion action at $\beta =6.2$. Using the $\rho$ mass to set the scale, we find hadron masses within two to three standard deviations of the experimental values (given in parentheses): $m_{K^{\ast }}=868\text{er}98$~MeV (892~MeV), $m_{\varphi }=970\text{err}2010$~MeV (1020~MeV), $m_N=820\text{err}9060$~MeV (938~MeV), $m_{\mathrm{\Delta }}=1300\text{errr}100100$~MeV (1232~MeV) and $m_{\mathrm{\Omega }}=1650\text{err}7050$~MeV (1672~MeV). Direct comparison with experiment for decay constants is obscured by uncertainty in current renormalisations. However, for ratios of decay constants we obtain $f_K\mathrm{/}{f}_{\pi }=1.20\text{er}32$ (1.22) and $f_{\varphi }\mathrm{/}{f}_{\rho }=1.13\text{er}23$ (1.22).