Results for the η′ mass from two-flavour lattice QCD

Abstract

We present results for the mass of the η′ meson for two-flavor lattice QCD in the continuum limit, calculated on the CP-PACS computer, using an RG-improved gauge action and clover fermion action with tadpole-improved c sw. Measurements are made at three couplings corresponding to a ≈ 0.22, 0.16, 0.11 fm for four quark masses corresponding to m π/ m ϱ ≈ 0.8, 0.75, 0.7, 0.6. The two-loop diagrams are evaluated using a noisy source method. Quark smearing for both one- and two- loop diagrams is successfully applied to obtain ground state signals in the η′ channel. We obtain m η′=0.960(87) −0.286 +0.036 in the continuum limit, where the second error represents the systematic uncertainty coming from varying the functional form for chiral and continuum extrapolations.