QED radiative corrections to e+e- --> f+f- with realistic cuts at LEP energies and beyond

TL;DR

This paper updates the calculation of QED radiative corrections for fermion pair production at LEP energies, improving the precision of theoretical predictions for cross sections and asymmetries with realistic experimental cuts.

Contribution

It provides a rederivation of O(alpha) Bremsstrahlung corrections for ZFITTER, enhancing agreement with other programs and analyzing effects at LEP 1 and LEP 2 energies.

Findings

Predictions at LEP 1 off-resonance shift by a few per mil.

At the Z resonance, numerical changes are negligible.

Discrepancies of several percent at LEP 2 energies with acollinearity cuts.

Abstract

After 10 years of steadily increasing the experimental precision at LEP/SLC, there is a strong demand on an update of existing programs for fermion pair production. We present a rederivation of the O(alpha) Bremsstrahlung corrections to e+e- --> f+f- for the semi-analytic program ZFITTER. We focus on observables like total cross section and forward-backward asymmetry in the leptonic case with combined cuts on acollinearity angle, acceptance angle, and minimal energy of the fermions. The outcome of our analysis is a shift of the predictions by ZFITTER at LEP 1 energies off-resonance of a few per mil while at the Z resonance numerical changes can be neglected. Thus we obtain for cross sections and asymmetries at LEP 1 a level of agreement with other programs of better than per mil, like for the kinematically simpler s' cut option. A preliminary analysis of ZFITTER, TOPAZ0, and other codes at LEP 2 energies showing deviations of several per cent with acollinearity cuts enforce a future examination of higher order effects with different cuts. The predictions by LEP/SLC data, however, are not affected within the experimental errors.