Bounds on universal new physics effects from fermion-antifermion production at LEP2

TL;DR

This paper develops a simple parametrization to set bounds on universal new physics effects in fermion-antifermion production at LEP2, using LEP1 and SLC data, and extends the approach to non-universal models.

Contribution

It introduces a new parametrization method for analyzing virtual effects of universal new physics using existing experimental data, and applies it to derive bounds from LEP2 measurements.

Findings

Derived explicit bounds on universal new physics effects from LEP2 data.

Showed the energy dependence of the parametrization functions is negligible.

Extended the method to certain non-universal new physics models.

Abstract

We consider lepton-antilepton annihilation into a fermion-antifermion pair at variable c.m. energy. We propose for this process a simple parametrization of the virtual effects of the most general model of new physics of \underline{universal} type. This parametrization is based on a recent approach, that uses the experimental results of LEP1, SLC as theoretical input. It introduces \underline{three} functions whose energy dependence is argued to be smooth and, in first approximation, negligible. A couple of representative models of new physics are considered, as a support of the previous claim. Explicit bounds are then derived for this type of new physics from the available LEP2 data, and a discussion is given of the relevance in this respect of the different experimental measurements. The method is then extended to treat the case of two particularly simple models of {\it non universal} type, for which it is possible to draw analogous conclusions.