Precision Experiments at LEP

TL;DR

The LEP collider's high-precision measurements confirmed key aspects of the Standard Model, influenced theories beyond it like Supersymmetry, and provided insights into fundamental particles and forces, shaping modern particle physics understanding.

Contribution

This paper reviews the impact of LEP's precision experiments on the validation of the Standard Model and the development of theories beyond it, such as Supersymmetry and Grand Unified Theories.

Findings

Confirmed the Standard Model with high precision

Excluded force unification within the SM

Supported supersymmetric extensions for dark matter candidate

Abstract

The Large Electron Positron Collider (LEP) established the Standard Model (SM) of particle physics with unprecedented precision, including all its radiative corrections. These led to predictions for the masses of the top quark and Higgs boson, which were beautifully confirmed later on. After these precision measurements the Nobel Prize in Physics was awarded in 1999 jointly to 't Hooft and Veltman "for elucidating the quantum structure of electroweak interactions in physics". Another hallmark of the LEP results were the precise measurements of the gauge coupling constants, which excluded unification of the forces within the SM, but allowed unification within the supersymmetric extension of the SM. This increased the interest in Supersymmetry (SUSY) and Grand Unified Theories, especially since the SM has no candidate for the elusive dark matter, while Supersymmetry provides an excellent candidate for dark matter. In addition, Supersymmetry removes the quadratic divergencies of the SM and {\it predicts} the Higgs mechanism from radiative electroweak symmetry breaking with a SM-like Higgs boson having a mass below 130 GeV in agreement with the Higgs boson discovery at the LHC. However, the predicted SUSY particles have not been found either because they are too heavy for the present LHC energy and luminosity or Nature has found alternative ways to circumvent the shortcomings of the SM.