Evidence for η′-π splitting in unquenched lattice QCD Original Research Article

We perform an extrapolation from negative to positive flavour numbers of full QCD lattice estimates of the η′ mass. The extrapolations are carried out by keeping ϱ and π masses at fixed values. We find an η′-π splitting which shows a flavour dependence consistent with the Witten-Veneziano formula based on the U(1) anomaly. The quantitative splitting is consistent with the estimates made in the quenched approximation.