Triangle loop for the Wilson fermion

The mass contribution and the axial anomaly for the triangle loop are calculated strictly for the Wilson fermion in the continuum limit. The external momenta in the denominators of triangle loop propagators play an important role in treating the infrared behavior for the massless case and deriving the correct mass contribution for the massive case. Neglect of this situation has sometimes brought about unusual results in the past. We get, as asserted by Karsten and Smit, the same result as in the continuum theory. (orig.)