Single and Pair Production of Neutral Electroweak Gauge Bosons at LEP

TL;DR

This paper reviews LEP results on neutral electroweak gauge boson production, highlighting new observations of gamma* and Z production, and discusses implications for physics beyond the Standard Model.

Contribution

It presents the first observations of gamma* and Z final states at LEP and combines data to measure Z pair production, setting limits on anomalous couplings.

Findings

First observation of gamma* and Z final states at LEP.

First significant measurement of Z pair production.

Limits on anomalous gammaZZ and ZZZ couplings.

Abstract

Recent LEP results on single and pair production of neutral electroweak gauge bosons are reviewed. QED and Electroweak gamma-e Compton scattering at LEP covers gamma-e center-of-mass energies sqrt{shat} in the range from about 20 GeV to 170 GeV, and leads to single production of on-shell gamma, off-shell gamma*, and Z bosons, also known as ``Zee'' process. The latter two final states have been observed for the first time by the OPAL collaboration, while the measurement of the scattered on-shell gamma's by L3 represents the highest energies at which QED Compton scattering has been studied so far. These processes can be used to set limits on excited electrons. Pair production of gamma* and/or Z at the e+e- center-of-mass energy sqrt{s}=183 GeV has been studied by the DELPHI, L3, and OPAL collaborations. The combination of these experiments yields the first significant measurement of Z pair production. With more statistics at higher energies, interesting limits on anomalous gammaZZ and ZZZ couplings can be derived from this process.