An update on vector boson pair production at hadron colliders

TL;DR

The paper delivers a full NLO QCD treatment of hadronic vector-boson pair production with leptonic decays, implemented in the MCFM Monte Carlo to capture spin correlations and enable realistic cuts. It updates total and leptonic-cross-section predictions for Tevatron Run II and the LHC using modern PDFs, and validates against prior results. Beyond the zero-width approximation, it discusses gauge-invariant width treatments for four-lepton final states and demonstrates practical applications to tri-lepton SUSY backgrounds and Higgs to WW searches. The work emphasizes that higher-order corrections and realistic cuts significantly affect backgrounds to new physics at hadron colliders, with cross sections generally larger than earlier estimates. Overall, it provides a crucial, publicly accessible tool for precise SM background calculations in collider phenomenology.

Abstract

We present numerical results (including full one-loop QCD corrections) for the processes p p-bar and pp -> W+ W-, W+/- Z/gamma* and Z/gamma* Z/gamma* followed by the decay of the massive vector bosons into leptons. In addition to their intrinsic importance as tests of the standard model, these processes are also backgrounds to conjectured non-standard model processes. Because of the small cross sections at the Tevatron, full experimental control of these backgrounds will be hard to achieve. This accentuates the need for up-to-date theoretical information. A comparison is made with earlier work and cross section results are presented for p p-bar collisions at sqrt{s}=2 TeV and pp collisions at sqrt{s}=14 TeV. Practical examples of the use of our calculations are presented.

Figures (4)

• Figure 1: Scale dependence of vector boson pair production cross sections.
• Figure 2: Energy dependence of vector boson pair production cross sections. The scale $\mu$ is taken to be the average vector boson mass.
• Figure 3: Doubly (a) and singly (b) resonant diagrams contributing to the parton-level process $q{\bar{q}} \to W^+W^- \to e^- {\bar{\nu}_e} \nu_\mu \mu^+$.
• Figure 4: The lepton invariant mass with the full $Z/\gamma^*$ interference (single hatched) and with the $Z$ only (double hatched). Each generated event is binned once for each opposite-sign, same-flavour lepton pair. Events which give rise to two entries are binned with half the event weight. The total cross-sections in the plot are $49.4$ fb and $42.6$ fb respectively.