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.