TOPAZ0 - a program for computing observables and for fitting cross sections and forward-backward asymmetries around the Z 0 peak

Abstract

The program TOPAZ0, which is designed for computing and fitting cross sections and forward-backward asymmetries of e + e - annihilation into fermion pairs and of Bhabha scattering around the Z 0 peak, is described. The various observables are computed over both a completely inclusive experimental set-up and a realistic one, i.e. with cuts on acollinearity, energy or invariant mass and angular acceptance of the outgoing fermions. Pure weak corrections at the one-loop level are included and leading higher-order corrections due to a potentially large top quark mass are taken into account. Depending on the experimental set-up initial state QED corrections are included by a convolution of the weakly corrected kernel distribution with a radiator function or with structure functions, where resummation of soft-photon effects and hard-photon emission up to O (α 2) are taken into account. Final state QED radiation, even in the presence of kinematical cuts, is treated analytically and exactly at O (α) and higher-order contributions are taken into account. QCD effects for the parameters of the Z 0 resonance and for s-dependent quantities are included. Recently proposed higher-order corrections, as initial state leptonic and hadronic pair production or O ( G 2 F m 4 t ), O (α s G Fm 2 t ), O (α 3 s), are taken into account as well. The program structure is highly modular and particular care has been devoted to computing efficiency and speed, both for annihilation and Bhabha channels.