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Manuscript Title: Monte Carlo simulation of two-photon processes. I. Radiative corrections to multiperipheral e+e-mu+mu- production.
Authors: F.A. Berends, P.H. Daverveldt, R. Kleiss
Program title: RADCOR
Catalogue identifier: AAFK_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 40(1986)271
Programming language: Fortran.
Computer: AMDAHL V7B.
Word size: 32
Keywords: Elementary, Particle physics, Event simulation, Two-photon process, Monte carlo simulation, Radiative corrections, Event generator, E+e-collision, Electron, Positron, Lepton, Photon, Quark.
Classification: 11.2.

Nature of problem:
Two-photon processes, such as e+e- -> e+e-mu+mu-, are in lowest order predominatly described by so-called multiperipheral or t-channel diagrams. Improvements on this description can be made by the calculations of the radiative corrections to these multiperipheral graphs. The MC program, presented here, does not only calculate the cross section with the radiative corrections on the electron or positron line included but can also produce unweighted events of the type e+e- -> e+e-mu+mu-(gamma) so that any experimental set-up can easily be simulated (especially in the no-tagging case).

Solution method:
The program is an event generator which gives sets of momenta of the outgoing particles, distributed according to the exact cross section. Every time the program is called, one event is returned. On the basis of the total approximate cross sections for soft (this includes the virtual corrections) and hard bremsstrahlung it is decided in the program which kind of event will be produced. In either case the event is first generated according to an approximate distribution. The approximations used are accounted for by the assignment of a weight to the events. Upon the application of a rejection algorithm we are left with unweighted events, satisfying the exact cross section.

Restrictions:
The program runs most efficiently in the no-tagging case. Single- tagging experiments can also be simulated by throwing away those events that do not satisfy the cuts. This, of course, reduces the efficiency of the MC program.

Running time:
2000 events/CPU minute.