ZZ' Mixing in Presence of Standard Weak Loop Corrections

We derive a method for a common treatment of Z' exchange, QED corrections, and weak loops. It is based on the form factor approach to the description of weak loop corrections to partial Z widths and cross sections. Problems connected with ZZ' mixing are discussed with special care. Our theoretical results are applied to the package ZFITTER. We demonstrate two different ways to the data analysis - one based on an extension of the standard model cross sections, the other on model-independent formulae together with the Z width calculations in presence of a Z'. With the resulting package ZEFIT+ZFITTER, LEP1 data from fermion pair production, including Bhabha scattering, can be analysed on, but also off the Z peak. Further, the code may be used at very high energies, e.g. in the region of a possible future linear e+e- collider.Comment: Latex, 24 pages, a typo in eqs. 23,24 correcte

On the massive two-loop corrections to Bhabha scattering

We overview the general status of higher order corrections to Bhabha scattering and review recent progress in the determination of the two-loop virtual corrections. Quite recently, they were derived from combining a massless calculation and contributions with electron sub-loops. For a massive calculation, the self-energy and vertex master integrals are known, while most of the two-loop boxes are not. We demonstrate with an example that a study of systems of differential equations, combined with Mellin-Barnes representations for single masters, might open a way for their systematic calculation.Comment: 8 pages, 2 figures, latex, Contribution to Proceedings of XXIX Conf. of Theoretical Physics: Matter to the Deepest, Ustron, Poland, 8-14 September 2005; preprint number adde

Automatized calculation of 2-fermion production with DIANA and aITALC

The family of two fermion final states is among the cleanest final states at the International Linear Collider (ILC) project. The package aITALC has been developed for a calculation of their production cross sections, and we present here benchmark numerical results in one loop approximation in the electroweak Standard Model. We are using packages like QGRAF, DIANA, FORM, LOOPTOOLS for intermediate steps.Comment: Contribution to the proceedings of the International Conference on Linear Colliders (LCWS 04), Paris, April 19-23, 2004. 5 pages, 1 figure, 5 table

Status of Electroweak Corrections to Top Pair Production

We review the status of electroweak radiative corrections to top-pair production at a Linear Collider well above the production threshold. We describe the Fortran package topfit and present numerical results at sqrt(s) = 500 GeV, 1 TeV, and 3 TeV.Comment: 6 pages, LaTex, 2 tables, 1 figure, talk presented by T.R. at the Int. Workshop on Linear Colliders (LCWS 2002), 26-30 Aug 2002, Jeju Island, Kore