WWGENPV — A Monte Carlo event generator for four-fermion production in e+e− → W+W− → 4f Original Research Article

The Monte Carlo program WWGENPV, designed for computing distributions and generating events for the four-fermion process e+e− → W+W− → 4f is described. It is based on the calculation of the exact tree-level matrix element of the four-fermion reaction and includes initial-state radiation in the leading-log approximation within the structure function approach. The program can be used in a two-fold way: as a Monte Carlo integrator for weighted events, providing predictions for the total cross section, the W invariant-mass distribution, the radiative energy and invariant-mass loss; and as a true event generator of unweighted events, useful for simulation purposes.