New Types of Sub-Atomic Particles

The Department of Physics and Astronomy Colloquium: Dr. Stephen Olsen, University Department of Physics, to speak on "New Types Of Sub-Atomic Particles." The classification of strongly interacting particles (hadrons) as composites of quarks and antiquarks has been spectacularly successful. The hundreds of hadrons that were discovered during the past fifty years could be identified as either a quark-antiquark meson or a 3-quark baryon. However, in Quantum Chromodynamics (QCD), the theoretical underpinning of quarks, other combinations, such as 5-quark baryons (pentaquarks), 4-quark mesons (tetraquarks), and quark-antiquark-gluon mesons (qqg hybrids) are possible.

The identification of such states and studies of their spectra would provide new and unique insights into QCD and the properties of quarks. The KEK B-factory, designed and built to study matter-antimatter asymmetries, has, as an unexpected bonus, turned out to be a prolific source of new particles. A candidate tetraquark meson is the X(3872), a relatively long-lived meson with unusual properties that was discovered at KEKB in 2003.

More recently we have found another unusual state, which we call the Y(3940), with properties similar to expectations for a qqg hybrid. This talk will focus primarily on the X(3872) and the determination of its quantum numbers. It will be shown that it has no satisfactory quark-antiquark assignment and its properties closely match expectations for a tetraquark meson. I will also briefly describe what it is about the Y(3940) that makes it so intriguing. Prospects for new hadron spectroscopies of tetraquark and hybrid mesons will be discussed.

For future Colloquia, please go to http://www.phys.hawaii.edu/%7Ejgl/colloq.html

Ticket Information
Free

Event Sponsor
Physics and Astronomy, Manoa

More Information
Dr. John G. Learned, 956-2964, jgl@phys.hawaii.edu, http://www.phys.hawaii.edu/%7Ejgl/colloq.html

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