UConn Physics Colloquium
Discovery of the Pentaquark: An Exotic Baryon
The pentaquark is a fundamental particle made up of 4 quarks and one antiquark, as compared with baryons (3-quarks) and mesons (quark-antiquark) which encompass virtually all known strongly-interacting particles. Although pentaquarks, along with other multi-quark particles, can exist by the rules of QCD, none had been found before last year when one called the Q+ was announced by an experimental collaboration working at the SPring-8 facility in Japan. The Q+ is composed of 2 up quarks, 2 down quarks, and 1 anti-strange quark. It was predicted in 1997 by theoretical calculations using the chiral soliton model. The SPring-8 discovery sparked a number of other experimental announcements by ITEP, CLAS and SAPHIR collaborations. This talk will describe the theoretical motivation, the subsequent announcements by SPring-8 and CLAS collaborations (the speaker is a member of both experiments), and the theoretical speculations that followed. The announcement of the pentaquark received wide media coverage, some calling it a "new classification of matter". The implications of this discovery will be discussed briefly.
Friday, August 29, 2003
(Refreshments will be served immediately following the colloquium in the lobby outside the lecture hall)