Precise Predictions for Four-Fermion Production in Electron-Positron Annihilation

TL;DR

The dissertation addresses the need for precise $O( abla)$ electroweak corrections to four-fermion production in $e^+e^-$ annihilation via a gauge-invariant double-pole expansion. It develops a comprehensive analytical framework and a multi-channel Monte Carlo tool (RacoonWW) that combines factorizable and non-factorizable corrections, including the complete bremsstrahlung process and dipole subtraction for soft/collinear singularities. A pivotal choice is the complex-mass width scheme, which preserves Ward identities and enables consistent treatment of finite-width effects within the DPA; the work also provides extensive numerical results and cross-checks against established calculations. Overall, the approach yields a practical, high-precision generator for LEP2-era analyses and future linear-collider studies of W-boson properties and triple/quartic gauge couplings, with non-factorizable effects shown to be small at LEP2 but potentially relevant at higher energies.

Abstract

The complete O(alpha) electroweak radiative corrections to e+e- --> WW --> 4f in the electroweak Standard Model are presented in the double-pole approximation. We give analytical and numerical results for the non-factorizable corrections and express the factorizable virtual corrections in terms of the known corrections to on-shell W-pair production and W decay. The full matrix elements to the lowest order processes e+e- --> 4f+gamma are taken into account for the real corrections. The matching of soft and collinear singularities between virtual and real corrections is done using the subtraction method. A Monte Carlo generator is constructed which corresponds to the subtraction branch of RacoonWW. Various numerical results are presented.

Figures (2)

• Figure 1: Diagrams with two resonant ${\rm W}$-boson propagators contributing to ${\rm e^+}$ e^+${\rm e^-}$ e^-$\to 4f$
• Figure 2: Generic diagrams for ${\rm e^+}$ e^+${\rm e^-}$ e^-$\to 4f$