ZZ' Mixing and Radiative Corrections at LEP I

Abstract

We present a method for a common treatment of $Z^{\prime }$ exchange, QED corrections, and weak loops in $e^{+}{e}^{-}$ annihilation. QED corrections are taken into account by convoluting a hard-scattering cross section containing $\gamma ,Z,$ and $Z^{\prime }$ exchange. Weak corrections and $Z{Z}^{\prime }$ mixing are treated simultaneously by a generalization of weak form factors. Using the properly extended Standard Model program for the $Z$ line shape, ZFITTER, we perform and compare two different analyses of the 1990 LEP~I data in terms of theories based on the E${}_6$-group and in terms of LR-symmetric models. From the LEP~I data alone, the $Z{Z}^{\prime }$ mixing angle may be limited to $|{\theta }_M|\le 0.01$ and the $Z^{\prime }$ mass to $M_2>118$--148 GeV, depending on the model (95\%~CL).

Comments: 12 pages, LaTex, 4 figures, a uuencoded file containing the latex file and figures is available via anonymous ftp at ftp://ftp.ifh.de/pub/preprint/cernth92-6545.uu ; paper publ. in Phys. Lett. B291 (1992) 187