Background Generators

A number of different Monte Carlo generators are used to produce simulation of the possible background events. For the ${\rm Z}^{0}/\gamma \rightarrow {\rm q}\bar{\rm q}$ events both PYTHIA and HERWIG are used. The two-photon events are much less well understood than the other processes and there are a number of different generators available, each of which model the processes slightly differently. Of the dedicated two-photon generators the PHOJET [86,87] generator is used to model some of the processes. In addition to PHOJET, the HERWIG and PYTHIA generators are also used to simulate some events. A combination of the three is used to produce the final sample of two-photon events.