1⁻⁺ exotic meson at light quark masses

Abstract

The mass of the 1⁻⁺ exotic meson, created with hybrid interpolating fields, is explored in numerical simulations of quenched QCD on large (20³×40) lattices to obtain good control of statistical and finite volume errors. Using the Fat-Link Irrelevant Clover (FLIC) fermion action, the properties of the 1⁻⁺ are investigated at light quark masses approaching 25 MeV (mπ/mρ≃1/3). Under the standard assumption that the coupling to the quenched a1η′ channel comes with a negative metric, our results indicate that the 1-+ exotic exhibits significant curvature close to the chiral limit, suggesting previous linear extrapolations have overestimated the mass of the 1⁻⁺. We find for the first time in lattice studies a 1⁻⁺ mass consistent with the π1(1600) candidate. We also find a strangeness ±1 JP=1- state with a mass close to 2 GeV.