Hadron Spectroscopy: Where Do We Stand ?
Abstract
It is widely accepted that QCD is most probably the correct theory of strong interactions. But a major aim of QCD is still unfulfilled: to provide the theory of quark confinement. To understand confinement and strong QCD it is necessary to understand the meson as well as the baryon spectrum. One of the important questions in this respect is what the relevant degrees freedom are which determine the spectrum of hadrons. Lattice QCD makes e.g. a quite exciting prediction; not only quark but also gluonic degrees of freedom should play a role in the hadronic spectrum. A whole spectrum of glueballs (gg-states) and hybrids (qbarqg-states) are predicted to exist. Finding these states and determining their spectrum would give us more insight on how confinement works. In general constituent quark models provide a good description of the hadron spectrum. However there is e.g. an interesting controversy in baryon spectroscopy. Constituent quark model calculations predict much more baryon resonances than have been observed so far. To find these missing resonances is one of the aims of photoproduction experiments. If these states do not exist this might question our understanding of baryons as consisting of three "equal" quarks and would maybe hint to a quark-diquark structure instead. Recent experimental progress in the search for gluonic excitations, "missing" baryon resonances and in hadron spectroscopy in general will be discussed.
- Publication:
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APS April Meeting Abstracts
- Pub Date:
- April 2002
- Bibcode:
- 2002APS..APR.E4001T