TOPAZ0 4.0 - A new version of a computer program for evaluation of de-convoluted and realistic observables at LEP 1 and LEP 2

Abstract

The program TOPAZ0 was developed for computing a variety of physical observables which are related to the e+e- annihilation into fermion pairs and to the large angle Bhabha scattering around the Z resonance. Among them, the Z parameters or pseudo-observables, the de-convoluted cross sections and those dressed with QED radiation, and finally the forward-backward asymmetries. The calculations are performed both for a completely inclusive experimental set-up and for a realistic one, i.e. a set-up with cuts on the acollinearity angle, on the energy of the outgoing fermions or on their invariant mass and angular acceptance. The new version, 4.0, includes several innovative features. First of all, the most important new capabilities since previous versions are recently computed electroweak and QCD correction factors that are relevant at the Z resonance in the light of the present experimental accuracy. Among them, the effect of the next-to-leading O(alpha^2 m_t^2) corrections and those radiative corrections to the hadronic decay of the Z which provide complete corrections of O(alpha alpha_s) to Gamma(Z --> q\bar{q}) with q=u,d,s,c and b. Secondly, the program has been upgraded to cover two-fermion final states at LEP 2 energies, where some of the assumptions made for earlier versions are no longer valid. In particular, to this aim all the electroweak radiative corrections that are negligible at the Z peak, but relevant far from it, have been added for s-channel processes, e.g. purely weak boxes, next-to-leading O(alpha^2) and leading O(alpha^3) QED corrections.