PYTHIA and HERWIG

PYTHIA [84] and HERWIG [85] are general purpose Monte Carlo generators for multi-particle production in high energy physics. They can both generate the four-fermion final states via the ${\rm e}^{+}{\rm e}^{-} \rightarrow {\rm W}^{+}{\rm W}^{-} \rightarrow f_{1}\bar{f}_{2}f_{3}\bar{f}_{4}$ process. Being general purpose generators that can produce events for proton-proton and electron-proton colliders as well as electron-positron colliders, they do not contain the detailed modelling of all the specific corrections that are contained in the dedicated four-fermion generators. Both generators only generate events with Standard Model couplings.