YFS2 - THE 2ND-ORDER MONTE-CARLO PROGRAM FOR FERMION PAIR PRODUCTION AT LEP SLC, WITH THE INITIAL STATE RADIATION OF 2 HARD AND MULTIPLE SOFT PHOTONS

A Monte Carlo program simulating fermion pair production is presented. It features multiphoton bremsstrahlung out of the initial state beams. The contributions from soft photons are summed rigorously up to an infinite order using the Yennie-Frautschi-Suura method while the contributions from up to two hard photons are also properly treated. Four momenta of all soft and hard photons are explicitly generated and the total energy momentum conservation is exactly obeyed. The program is primarily aimed for LEP/SLC type experiments and will be helpful in the precise measurements of the Z0 mass and width, the basic parameters in precision tests of standard electroweak theory. It can also be used far away from the Z0 resonance as well. From the point of view of the QED, it provides the total cross section with precision 0.1% near the Z0 and 0.5% away from the Z0 resonance. With some restriction it can provide predictions for various asymmetries. © 1990.