The ALEPH experiment

Abstract

Alep detector must be designed to address the known physics potential of the accelerator and be sufficiently flexible to accommodate the unexpected. This was the foundation for the design of aleph. lep provides the opportunity to make the most sensitive tests of the Standard Model of electroweak interactions which will probably ever be possible. The first requirement of the detector must therefore be to ensure it has the capability to make these precise tests of the electro weak theory. Testing the Standard Model at lep will take place at the following two energies. 1 .At the Z peak ( lep 1 at a centre of mass energy ca. 90 GeV). At this energy the electron and positron annihilate to form real Z bosons. This enables the Z mass, width and couplings to leptons and quarks to be determined with very high precision. Annihilations with longitudinally polarized electron and positron beams will eventually allow additional stringent tests. 2. Above the WW threshold (lep 2at a centre of mass energy ca. 190 GeV). At this energy the emphasis will be on the charged gauge boson, its mass, its couplings to fermions and the non-abelian ZWW coupling. Investigation of longitudinal Ws, which result directly from the Higgs mechanism, will be possible. The detector must therefore be designed to handle the increased complexity and energies of interactions at lep 2 as well as those at the Z peak.