Do Present LEP Data Provide Evidence for Electroweak Corrections?

Abstract

The Born approximation, based on $\bar{\alpha }\equiv \alpha (m_Z)$ instead of $\alpha$, reproduces all electroweak precision measurements within their $(1\sigma )$ accuracy. The low upper limits for the genuinely electroweak corrections constitute one of the major achievements of LEP. The astonishing smallness of these corrections results from the cancellation of a large positive contribution from the heavy top quark and large negative contributions from all other virtual particles. It is precisely the non-observation of electroweak radiative corrections that places stringent upper and lower limits on the top mass.

Comments: 12 pages, preprint CERN-TH.6943/93