ZFITTER -- An Analytical Program for Fermion Pair Production in e+e- Annihilation

TL;DR

ZFITTER is a semi-analytical software tool designed for precise calculations of fermion pair production in electron-positron annihilation, incorporating comprehensive QED and weak corrections, and supporting flexible analysis configurations.

Contribution

It introduces a versatile framework with multiple calculation chains and branches, enabling detailed and customizable modeling of fermion pair production processes.

Findings

Accurately computes cross sections and asymmetries.

Includes complete ${ m O}( ext{alpha})$ weak loop corrections.

Supports various interfaces for parameter fitting.

Abstract

We describe how to use ZFITTER, a program based on a semi-analytical approach to fermion pair production in e+e- annihilation and Bhabha scattering. A flexible treatment of complete ${\cal O}(\alpha)$ QED corrections, also including higher orders, allows for three calculational {\bf chains} with different realistic sets of restrictions in the photon phase space. {\tt ZFITTER} consists of several {\bf branches} with varying assumptions on the underlying hard scattering process. One includes complete ${\cal O}(\alpha)$ weak loop corrections with a resummation of leading higher-order terms. Alternatively, an ansatz inspired from S-matrix theory, or several model-independent effective Born cross sections may be convoluted. The program calculates cross sections, forward-backward asymmetries, and for $\tau$~pair production also the final-state polarization. Various {\bf interfaces} allow fits to be performed with different sets of free parameters.