These processes represent the production of a diboson pair V _{1}V _{2}, where V _{1}
and V _{2} may be either a W or Z∕γ^{*}. All the processes in this section may
be calculated at NLO with the exception of nproc=69. There are various
possibilities for the subsequent decay of the bosons, as specified in the sections
below. Amplitudes for the V _{1}V _{2} process at O(α_{s}) are taken from ref. [1].
We also include singly resonant diagrams at NLO for all processes in the
case zerowidth = .false.. For more details on this calculation, please see
Refs. [2, 3].

For processes 62, 63, 64, 65, 74 and 75 the default behaviour is that the hadronic decay products of the bosons are clustered into jets using the supplied jet algorithm parameters, but no cut is applied on the number of jets. This behaviour can be altered by changing the value of the variable notag in the file src/User/setnotag.f.

Calculations of processes 61, 71, 76, 81 and 82 can be performed at NLO by
subtraction, zero-jettiness slicing and q_{T}-slicing. They can be computed at NNLO
using zero-jettiness slicing and q_{T}-slicing, as described in ’Non-local slicing
approaches for NNLO QCD in MCFM’,[4]. For processes 61, 81 and 86 the NNLO
corrections include glue-glue initiated box diagrams which first contribute at
order α_{s}^{2}. Two loop results for virtual diagrams at O(α_{s}^{2}) are taken from
[5].

This process can be calculated at LO, NLO, and NNLO. NLO calculations can be
performed by subtraction, zero-jettiness slicing and q_{T}-slicing. NNLO calculations
can be performed by zero-jettiness slicing and q_{T}-slicing.

Full account is taken in this process of the interference between diagrams generated by the exchange of two positrons. This leads to a more complicated resonance structure in the phase space.

nplotter_VV.f is the default plotting routine.

[1]
L.J. Dixon,
Z. Kunszt
and
A. Signer,
Helicity
amplitudes
for
O(α_{s})
production
of
W^{+}W^{-},
W^{±}Z,
ZZ,
W^{±}γ,
or
Zγ
pairs
at
hadron
colliders,
Nucl.
Phys.
B531
(1998)
3
[hep-ph/9803250].

[2] J.M. Campbell and R.K. Ellis, An Update on vector boson pair production at hadron colliders, Phys. Rev. D 60 (1999) 113006 [hep-ph/9905386].

[3] J.M. Campbell, R.K. Ellis and C. Williams, Vector boson pair production at the LHC, JHEP 07 (2011) 018 [1105.0020].

[4] J.M. Campbell, R.K. Ellis and S. Seth, Non-local slicing approaches for NNLO QCD in MCFM, 2202.07738.

[5]
T. Gehrmann,
A. von
Manteuffel
and
L. Tancredi,
The
two-loop
helicity
amplitudes
for
qq^{′}→ V _{1}V _{2} → 4
leptons,
JHEP
09
(2015)
128
[1503.04812].