PoS(HEP2005)399 Physics Beyond the Standard Model † Riccardo Rattazzi∗ CERN, Switzerland E-mail:
[email protected] I review recent theoretical work on electroweak symmetry breaking International Europhysics Conference on High Energy Physics July 21st - 27th 2005 Lisboa, Portugal ∗Speaker. †On leave from INFN, Sezione di Pisa, Italy. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it/ Physics Beyond the Standard Model Riccardo Rattazzi 1. Introduction I have been assigned this broad title but my talk will be mostly concerned with the origin of the electroweak scale. I will attempt to give an overview of the theoretical ‘laborings’ that came up after the end of the LEP era and in preparation to the commissioning of the LHC. An appropriate subtitle for my talk could thus be ‘Electroweak Symmetry Breaking after LEP/SLC’. There are two different sides from which to regard the legacy of LEP/SLC, and forming what is also known as the LEP paradox [1]. From one side it is an impressive triumph of human endeavour: the Standard Model (SM) is a complete theory of fundamental processes successfully tested at PoS(HEP2005)399 the per-mille precision. That means that small quantum corrections to the Born approximation are essential in the comparison between theory and experiment. However, when regarded from the other side, this great success becomes a huge conceptual bafflement, because the hierarchy problem, which inspired theoretical speculations for the last three decades, suggested that the SM should be overthrown right at the weak scale.