Toward a model-independent analysis of electroweak data

Abstract

We set the framework for a model-independent analysis of the data on electroweak precision tests. Starting from three basic observables, the mass ratio m_w / m_z, the Z partial width and the forward-backward asymmetry for changed leptons, we define three dimensionless parameters ϵ₁, ϵ₂ and ϵ₃ which contain the snall radiative correction effects one is interested in, with large m_t-effects only appearing in ϵ₁. The results on the epsilons implied by the present experimental data are discussed as well as the predictions of the Standard Model, as functions of m_t and m_H, with special attention to evaluating the theoretical errors. We formulate a hierarchy of simple and general assumptions, valid in large classes of models, which are needed in order to relate the epsilons to an increasingly larger set of observables including the τ-polarisation asymmetry, the forward-backward asymmetry for the b-quark, deep inelastic neutrino scattering and atomic parity violation. Correspondingly the analysis of present data is performed in stages and the conclusions are examined at each stage. Finally the case of the Standard Model is recovered as a very relevant particular example.