Neutral-Current Four-Fermion Production in e+e- Interactions at LEP

TL;DR

This study measures neutral-current four-fermion production in electron-positron collisions at LEP energies, confirming Standard Model predictions and searching for new particles without finding evidence.

Contribution

First measurement of four-fermion production cross sections at LEP energies, including the Zgamma* process, with results consistent with the Standard Model.

Findings

Measured cross sections agree with Standard Model predictions.

The Zgamma* process cross section at 196.6 GeV is 0.29 pb.

No evidence for new neutral heavy particles was observed.

Abstract

Neutral-current four-fermion production, e+e- -> ffff is studied in 0.7/fb of data collected with the L3 detector at LEP at centre-of-mass energies root(s)=183-209GeV. Four final states are considered: qqvv, qqll, llll and llvv, where l denotes either an electron or a muon. Their cross sections are measured and found to agree with the Standard Model predictions. In addition, the e+e- -> Zgamma* -> ffff process is studied and its total cross section at the average centre-of-mass energy 196.6GeV is found to be 0.29 +/- 0.05 +/- 0.03 pb, where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model prediction of 0.22 pb. Finally, the mass spectra of the qqll final states are analysed to search for the possible production of a new neutral heavy particle, for which no evidence is found.