Nature of the a_1 meson in lattice quantum chromodynamics studied with chiral fermions

We study the a_1 meson using a quenched lattice quantum chromodynamics simulation with the truncated overlap fermions formalism based on the domain wall fermions. The obtained lightest mass of the a_1 meson, 1272(45) MeV, is consistent with the experimental value for a_1(1260). Thus, a_1(1260) can be identified to have a simple two-body constituent-quark structure. Our quenched simulation result of a_1(1420) can not explain the experimental mass value, which suggests a_1(1420) is not a simple qq̅ two quark state.