ZFITTER v.6.21: A semi-analytical program for fermion pair production in e(+)e(-) annihilation

We describe ZFITTER. a Fortran program based on a semi-analytical approach to fermion pair production in e(+)e(-) annihilation at a wide range of cent re-of-mass energies, including the PETRA. TRISTAN, LEP1/SLC, and LEP? energ ies. A flexible treatment of complete O(alpha) QED corrections and of some higher order contributions is made possible with three calculational chains containing different realistic sets of restrictions in the photon phase sp ace. Numerical integrations are at most one-dimensional. Complete O(alpha) weak loop corrections supplemented by selected higher-order terms may be in cluded. The program calculates Deltar. the Z width, differential cross-sect ions, total cross-sections, integrated forward-backward asymmetries, left-r ight asymmetries, and for tau pair production also final-state polarization effects. Various interfaces allow fits to be performed with different sets of free parameters. (C) 2001 Elsevier Science B.V. All rights reserved.