Pentaquark search at Jefferson Laboratory

Abstract

The search for baryon resonances with the strangeness quantum number S=+1 that cannot be formed by three quarks has a long history. In the last year, several experimental groups have reported evidence for a S=+1 baryon state, with mass ranging from 1.52 and 1.55 GeV and width less than 25 MeV, by looking at the invariant mass of theKN system. This resonance has been identified with the lowest mass, the Θ+, of the anti-decuplet of pentaquark particles predicted some year ago within the chiral soliton model. At the same time there are a number of experiment, mostly at high energies, that report null results.