WW Cross-sections and Distributions

TL;DR

This paper surveys the theoretical landscape for WW production at LEP2, focusing on how to extract the W mass and test non-abelian gauge couplings. It delineates a progression from on-shell WW production with full ${\cal O}(\alpha)$ corrections to off-shell four-fermion final states, highlighting challenges with gauge invariance and the role of radiative corrections, particularly initial-state radiation and Coulomb effects, through the pole-scheme framework. The work documents the development of practical approximations (IBA, structure-function ISR, and Coulomb resummation) and assesses their accuracy, while addressing the impact of W width and reconnection/Bose–Einstein effects on precision measurements. The findings underscore the importance of incorporating dominant RCs to achieve percent-level predictions, enabling precise $M_W$ determinations and robust tests of triple gauge couplings, with Higgs-mass and top-quark contributions as notable theoretical uncertainties.

Abstract

We present the results obtained by the "WW Cross-sections and Distributions" working group during the CERN Workshop "Physics at LEP2" (1994/1995)

Figures (10)

• Figure 1: Lowest-order diagrams for ${\rm e^-}$${\rm W^+}$${\rm W^-}$${\rm e^+}$ e^+${\rm e^-}$ e^-$\to{\rm W^+}$ W^+${\rm W^-}$ W^-$$.
• Figure 2: Unpolarized total cross-section in the threshold region. The dotted curve corresponds to Born, the dashed one to _μ$G_\mu$-Born, and the solid one to the results including full radiative electroweak (α)${\cal{O}}(\alpha)$ corrections.
• Figure 3: Unpolarized differential cross-section ${{\rm d}}\sigma/({{\rm d}}\!\cos\theta_+)$ at $\sqrt{s}=190\,{\rm GeV}$ GeV$$. The same signature as adopted in figure \ref{['totthr']}.
• Figure 4: Lowest-order diagrams for ${\rm e^+}$ e^+$\to{\rm W^+}$ W^+${\rm W^-}$ W^-$$${\rm e^+}$${\rm e^-}$${\rm W^+}$${\rm W^-}$$\to4f$
• Figure 5: Example of a singly-resonant diagram.