These processes represent the production of a diboson pair V 1V 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 1V 2 process at O(αs) 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 qT-slicing. They can be computed at NNLO using zero-jettiness slicing and qT-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 αs2. Two loop results for virtual diagrams at O(αs2) 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 qT-slicing. NNLO calculations can be performed by zero-jettiness slicing and qT-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(αs) 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 1V 2 → 4 leptons, JHEP 09 (2015) 128 [1503.04812].