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

Photon collimator system for the ILC Positron Source

High energy e+e- linear colliders are the next large scale project in particle physics. They need intense sources to achieve the required luminosity. In particular, the positron source must provide about 10E+14 positrons per second. The positron source for the International Linear Collider (ILC) is based on a helical undulator passed by the electron beam to create an intense circularly polarized photon beam. With these photons a longitudinally polarized positron beam is generated; the degree of polarization can be enhanced by collimating the photon beam. However, the high photon beam intensity causes huge thermal load in the collimator material. In this paper the thermal load in the photon collimator is discussed and a flexible design solution is presented.Comment: 22 pages, 19 figures, 8 tables, cross-reference to table 4 fixe