Tests of the Standard Model and Constraints on New Physics from Measurements of Fermion-Pair Production at 189-209 GeV at LEP

TL;DR

This paper reports precise measurements of fermion-pair production at LEP energies, testing the Standard Model and setting limits on new physics such as contact interactions and additional Z bosons.

Contribution

It provides new measurements of cross-sections and angular distributions at 189-209 GeV, and uses these to constrain extensions to the Standard Model.

Findings

Measured cross-sections agree with Standard Model predictions.

Determined the electromagnetic coupling constant at LEP2 energies.

Set limits on new physics like contact interactions and heavy Z bosons.

Abstract

Cross-section and angular distributions for hadronic and lepton-pair final states in e+e- collisions at centre-of-mass energies between 189 GeV and 209 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The measurements are used to determine the electromagnetic coupling constant alphaem at LEP2 energies. In addition, the results are used together with OPAL measurements at 91-183 GeV within the S-matrix formalism to determine the gamma-Z interference term and to make an almost model-independent measurement of the Z mass. Limits on extensions to the Standard Model described by effective four-fermion contact interactions or the addition of a heavy Z boson are also presented.