e+e− physics and the standard model
Elliot Leader, E. Predazzi · Cambridge University Press eBooks · 1996
The recent story of narrow resonance discoveries (see Chapter 11) has shown how the properties of systems with quantum numbers of the photon (1 −− ) can best be studied with e + e - colliders. In this chapter we review some of the information that has come from e + e - machines. In particular, we shall see what support they provide for the SM. We also discuss the perspective for future e + e - colliders. Electron-positron storage rings The ideal tools for studying the spectroscopy of the new vector meson particles have undoubtedly been the various e + e - colliding beam machines: SPEAR at SLAC, DORIS at DESY (Deutsches Elektronen Synchrotron), PETRA at DESY and, more recently, SLC at Stanford and LEP 1 at CERN though the actual discovery (Aubert et al ., 1974; Herb et al ., 1977; UA1, 1983; UA2, 1983) of some of these particles occurred on the proton machines (Brookhaven, Fermilab and CERN). The reason for the latter lies in the narrowness of these particles; one can simply miss them as one varies the energy. On the other hand, once discovered, the fact that J /Ψ(3097), ϒ(9.46) and the Z are vector particles 1 –– , and thus couple naturally to a virtual photon, makes an e + e - machine particularly efficacious since the main channel of e + e - annihilation is into a virtual photon. Thus, it is rather difficult in an e + e - machine to sit right on top of one of these very narrow resonances whose width may be much smaller than the energy resolution of the machine itself.