Towards an effective-action approach to fermion-loop corrections Original Research Article

We present a study of the effective action approach to incorporate higher-order effects in e+e−→n fermions. In its minimal version, the effective action approach is found to exhibit problems with unitarity and high-energy behaviour. We identify the origin of these problems by investigating the zero-mode solutions of the Ward identities. A numerical analysis of the importance of the zero-mode solutions is presented for four-fermion production processes.