In the past two years more than 13 experiments have reported observation of a narrow exotic S=+1 baryon state in the mass range from 1.525 to 1.55 GeV/c2. The minimal quark content of this state, now called the Î˜+, is uudds. In contrast to almost fully exclusive experiments at low energies that have reported evidence for the Î˜+, there have been a number of reports of non-observation of this state, mostly in high energy inclusive experiments. The main criticisms of the reported Î˜+ signals are insufficient statistics, and variation in mass. Evidence for the doubly strange, Î¦-- (known as Îž--),and for the charmed, Î˜c, pentaquarks have been presented only in the single experiments.
The CLAS Collaboration at Jefferson Laboratory has published two papers on the experimental evidence for the Î˜+ and Îž--. These data now represent the world's largest data sets for photoproduction on hydrogen and deuterium. In this talk an overview of the experimental situation on the pentaquarks and the preliminary results of high statistics CLAS experiments will be presented.