Model Independent Z′Z' Constraints at Future e+e−e^+e^- Colliders}

Model independent constraints on the mass of extra neutral gauge bosons and their couplings to charged leptons are given for LEP~II and a 500\,GeV $e^+e^-$ collider. Analytical exclusion limits are derived in the Born approximation. The $Z'$ limits obtained with radiative corrections are always worse than those calculated at the Born level. Polarized beams are only useful for degrees of polarization essentially larger than 50\%. Known discovery limits on extra $Z$ bosons predicted by popular $Z'$ models are reproduced as special cases. The $Z'$ constraints are compared to those predicted by four fermion contact interactions.Comment: 10 Latex pages, uses epsf.sty, 5 uuencoded figures obtainable via anonymous ftp from convex.ifh.de in /pub/preprint/ as file desy93-154.uu, DESY 93-15

Experimental Constraints on the Scale of New Physics in Top Condensate Models

We obtain mass limits on the extra neutral gauge boson which is predicted in a model with hidden gauge symmetry and dynamical breaking of the electroweak symmetry by a top quark condensate. For typical model assumptions, present LEP data exclude masses below 3\,TeV. With LEP200 or an electron-positron collider of a c.m. energy of 500 GeV masses below 15\,TeV or 50\,TeV could be excluded, respectively. Such high mass limits allow the calculation of the observables used in the analysis in the context of the Nambu-Jona-Lasinio model.Comment: 7 pages, 2 figures(appended as PS files), DESY 93-111, LMU-04/9

Searching for a W' at the Next-Linear-Collider using Single Photons

We examine the sensitivity of the process e+e- -> nu nubar + gamma to additional W-like bosons which arise in various models. The process is found to be sensitive to W' masses up to several TeV.Comment: 8 pages, 8 figures, Latex. To appear in proceedings of "MRST '99: High Energy Physics at the Millenium", May 10-12, 1999, Carleton U., Ottawa (AIP

Model-Independent Z′Z' Limits from Electron-Electron Collisions

Model independent constraints on the mass of an extra neutral gauge boson and its couplings to charged leptons are given for the $e^-e^-$ option of a future linear collider. Analytic exclusion limits are derived in the Born approximation. The results are compared with those of the $e^+e^-$ mode. The influence of radiative corrections is discussed.Comment: 7 pages, LaTeX, 4 Figures, uuencoded Postscriptfile, MPI-Ph/94-23, LMU-04/9

THE PROCESS e+e−→llˉqqˉe^+ e^- \rightarrow l \bar l q \bar q AT LEP AND NLC

The cross sections for the reaction $e^+ e^- \rightarrow l \bar l q \bar q$ and for similar four fermion production processes at LEP~1, LEP~2 and the NLC are calculated. Due to the extraordinary symmetry properties of the process, very compact analytical formulae describe the double differential distributions in the invariant masses of the $l \bar l$ and $q \bar{q}$ pairs. The total cross sections may be obtained with two numerical integrations.Comment: 10 pages (LaTeX), 1 table, 4 figures (not included, a uuencoded file containing the LaTeX and all postscript files is available via anonymous ftp from convex.ifh.de as /pub/preprint/desy94-185.uu), DESY 94-18