Subatomic Physics

312 The Electromagnetic Interaction
Table 10.2: Some Existing and Planned Colliders.
Ring Location Start of Particles Max Beam Energy
operations collided (GeV)
CESR Cornell 1979 e + e − 6/6
VEPP-4M Novosibirsk 1994 e + e − 6/6
BEPC Beijing 1989 e + e − 2/2
LEP CERN 1989 e + e − 105/105
DAΦNE Frascati 1999 e + e − 1/1
KEKB Tokyo 1999 e + e − 4/8
PEP-II Stanford 1999 e + e − 3/9
ILC Undecided e + e − 2000/2000
HERA Hamburg 1992 ep 30/920
Tevatron Batavia 1987 pp 980/980
LHC CERN 2007 pp 7000/7000
Consequently, detectors are
designed to observe essentially
all events. The basic
arrangement is given in
Fig. 10.19; the detector that
was crucial for the discovery
of the ψ and thus of
charm at SPEAR is shown
in Fig. 10.20. (12) Fig. 10.19
illustrates another interesting
feature of e + e− Figure 10.19: Basic arrangement for detectors at colliders.
collisions:
the resonances can decay by
emitting qq pairs that subsequently
appear mostly as
back-to-back jets.
Table 10.2 shows that the highest energies are achieved in collisions of hadrons.
Thus the Tevatron was built and the LHC is being built to search for new physics
in pp and pp collisions, respectively. However, e + e− colliders produce experiments
that are much easier to interpret and yield cleaner probes of new physics: the
International Linear Collider (ILC) is presently in the planning stage even though
its energy will be a fraction of the energy that LHC will reach.
12 Other detectors are described in Chapter 4.