Towards an effective-action approach to fermion-loop corrections

Abstract

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.

Comments: 43 pages, 1 figure. Accepted for publication in Nuclear Physics B