Flavor singlet meson mass in the continuum limit in two-flavor lattice QCD

We present results for the mass of the eta[prime] meson in the continuum limit for two-flavor lattice QCD, calculated on the CP-PACS computer, using a renormalization-group-improved gauge action, and the Sheikoleslami-Wohlert fermion action with a tadpole-improved csw. The correlation functions are measured at three values of the coupling beta corresponding to the lattice spacing a[approximate]0.22, 0.16, 0.11 fm and for four values of the quark mass parameter kappa corresponding to mpi/mrho[approximate]0.8, 0.75, 0.7, 0.6. For each (beta, kappa) pair, 400–800 gauge configurations are used. The two-loop diagrams are evaluated using a noisy source method. We calculate eta[prime] propagators using both smeared and local sources, and find that excited state contaminations are much reduced by smearing. A full analysis for the smeared propagators gives meta[prime]=0.960(87)-0.248+0.036 GeV in the continuum limit, where the second error represents the systematic uncertainty coming from varying the functional form for chiral and continuum extrapolations