Background
Empirical hadron spectroscopy (EHS) is the study -
by inductive, not deductive methods - of the structure and
interactions of heavy matter at the subatomic level. A
primary historical example of the inductive approach was
the construction of the Mendeleev table of elements,
systematized from similarities in chemical behavior: an
edifice well-founded before electrons and nuclei were
known, but conducive to their discovery. A corresponding
pursuit at the quark level promises to be essentially
limitless because of the color restriction that quarks are
always bound and hence can rise in principle to infinitely
excited states. Because at some high levels these states
may become unresolvable, experiments at relatively low
masses must establish empirical formulae that bear reliable
extrapolation.
EHS experimentation is a widely and thinly spread
activity. There are few laboratories or university
departments dedicated mainly to this subject: the cadre
consists largely of small institutional subgroups scattered
over the globe. Fortunately, the advent of electronic
communication has been a strong agent for cohesiveness -
as have been several international forums that schedule
regular meetings at intervals of order two years. The most
relevant of these is the Hadron XX series in odd calendar
years; while LEAR was running at CERN, a regular sequence
of even-year LEAP conferences provided much light meson
spectroscopy.
As a local adjunct to this community, three or four Summer
courses like EHSW-00 have been presented at the University
of Maryland over the past decade. They were not large but,
were well received by the participants.
During that period, however, the fragile structure
of international EHS has been threatened by severe
reduction of experimental facilities. Primary data sources
had been the major international accelerator laboratories:
- electron-positron colliders at Beijing, Cornell, Frascati,
Saclay, Stanford, Novosibirsk;
- hadron (pion, kaon, proton,
antiproton) bombardment of mostly hydrogen targets at BNL,
CERN, Dubna, FNAL, Harwell, KEK,
IHEP (Protvino);
- and electronuclear excitation at Jefferson Laboratory and SLAC.
Of more than a dozen productive establishments, only five
(Beijing, Cornell, JLab, Novosibirsk and Protvino) are now
active, although the Fermilab Booster and the Japan Hadron
Facility may become available for EHS in the next 5-10
years. Meanwhile, EHS is likely to suffer a major drought,
particularly among hadron-induced reactions.
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Updated June 7, 2004