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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 $β= 6.2$. Using the $ρ$ mass to set the scale, we find hadron masses within two to three standard deviations of the experimental values (given in parentheses): $m_{K^*}=868\er{9}{8}$~MeV (892~MeV), $m_ϕ=970\err{20}{10}$~MeV (1020~MeV), $m_N=820\err{90}{60}$~MeV (938~MeV), $m_Δ=1300\errr{100}{100}$~MeV (1232~MeV) and $m_Ω=1650\err{70}{50}$~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 $f_K/f_π=1.20\er{3}{2}$ (1.22) and $f_ϕ/f_ρ=1.13\er{2}{3}$ (1.22).