The search for QCD exotica
- Indiana Univ., Bloomington, IN (United States)
One of the open questions in non-perturbative QCD has to do with the existence of meson states predicted by the theory other than qq states. These include four-quark states (q{sup 2}q{sup 2} or molecules like KK), states of pure glue (glueballs: gg or ggg) and mixed or hybrid states (qqg). The prima facie candidate for a non-qq state would be one possessing exotic quantum numbers, J{sup PC}, not consistent with a qq combination. Examples include J{sup PC}=0{sup +-},{sup 0--},{sup -+},{hor_ellipsis} Remarkably, states with exotic quantum numbers have not been found despite intensive searches. The case for a possible sighting of an exotic J{sup Jc}= 1{sup -+} state decaying into {eta}{pi}{sup O}, made a few years ago, seems to be dissolving. Yet, the evidence for non-qq states is clearly present. Conventional qq nonets are over-subscribed, states have been found with decay modes or production characteristics peculiar for qq. The experimental lesson we have learned is that information from a number of complementary processes must be brought together in order to understand the meson spectrum. Information has come from e{sup +}e{sup -},{gamma}{gamma}, {gamma}{gamma}, and pp collisions, from vector meson decays and from peripheral and central hadroproduction. This talk will review the status of the experimental search. I will especially point out how new technology is being brought to bear on the re-visit of the light quark sector. New instrumentation allows for sophisticated and selective triggers. The recent explosion in computing power allows us to analyze data with unprecedented statistics. Preliminary results from a recently completed, ultra-high statistics experiment using the Multiparticle Spectrometer at Brookhaven Lab will be presented. I will also describe the extension of the search to CEBAF, where an approved experiment there will study the sub-structure of scalar mesons via the radiative decays of the ER meson.
- OSTI ID:
- 255416
- Report Number(s):
- CONF-9510116-; ISSN 0003-0503; TRN: 96:015721
- Journal Information:
- Bulletin of the American Physical Society, Vol. 40, Issue 10; Conference: Fall meeting of the Division of Nuclear Physics of the American Physical Society, Bloomington, IN (United States), 25-28 Oct 1995; Other Information: PBD: Oct 1995
- Country of Publication:
- United States
- Language:
- English
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