All electroweak four fermion processes in electron-positron collisions

TL;DR

The paper addresses the challenge of predicting electroweak four-fermion final states in $e^+e^-$ collisions with high precision, where final states arise from multiple gauge-boson production channels and many Feynman diagrams contribute. Its main approach uses spinor-helicity amplitude methods for massless fermions and a multichannel Monte Carlo generator to compute tree-level matrix elements and phase-space distributions across arbitrary experimental cuts. The authors classify final states, separate signal and background diagrams (including non-interfering backgrounds), and provide illustrative results showing backgrounds contributing up to 4–10% for certain channels, as well as addressing radiative corrections and their impact on cross sections. The work enables more accurate extraction of signals such as $W$-pair production and tests of gauge couplings, offering a general tool for four-fermion final states in current and future $e^+e^-$ colliders.

Abstract

This paper studies the electroweak production of all possible four fermion states in e+ e- collisions. Since the methods employed to evaluate the complete matrix elements and phase space are very general, all four fermion final states in which the charged particles are detected can be considered. Also all kinds of experimental cuts can be imposed. With the help of the constructed event generator a large number of illustrative results is obtained, which show the relevance of backgrounds to a number of signals. For LEP 200 the W-pair signal and its background are discussed, for higher energies also Z-pair and single W and Z signals and backgrounds are presented.