Study of Z Boson Pair Production in e+e- Collisions at LEP at \sqrt{s}=189 GeV

TL;DR

This study measures Z boson pair production cross sections in e+e- collisions at 189 GeV using LEP data, confirming Standard Model predictions and setting limits on anomalous neutral gauge boson couplings.

Contribution

It provides the first detailed measurement of Z pair production cross sections at this energy and constrains possible new physics beyond the Standard Model.

Findings

Measured total Z pair production cross section: 0.74 pb.

Enhanced analysis of b quark final states yields a cross section of 0.18 pb.

Results agree with Standard Model predictions and set limits on anomalous couplings.

Abstract

The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e+e- collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74 +0.15 -0.14 (stat.) +/- 0.04 (syst.) pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18 +0.09 -0.07 (stat.) +/- 0.02 (syst.) pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements.