Chiral anomaly in lattice QCD with twisted mass Wilson fermion

The flavour singlet axial Ward identity with Osterwalder-Seiler twisted mass Wilson fermion action is studied on a finite lattice, with finite fermion mass and the Wilson parameter r up to 1. Approach to the infinite volume chiral limit and emergence of the anomaly is significantly better than that obtained with O(a) and O(a2) improved fermion actions. We have shown explicitly that up to O(g2), parity violating terms cancel in the Ward identity even at finite volume and finite lattice spacing.