Search for the Exotic Pentaquark theta+ Baryon state in the gamma deuteron -> lambda theta+ reaction
Abstract
The discovery of an exotic pentaquark baryonic state with strangeness S=+1 has been one of the most exciting results in particle physics of last year. The existence of such a state have been predicted in 1997 by Diakonov and collaborators in the framework of the Chiral Quark Soliton model, with mass around 1.54 GeV and width less than 15 MeV. Due to its quark content, this state should be strongly coupled to K-nucleon decay channels. The experimental evidence for this exotic baryon first came from the observation of a narrow resonance in K- missing mass spectrum for the gamma n arrow K- K+ n reaction on Carbon. Confirmation of this results have been obtained in a series of different measurements: in photoproduction experiment with proton and nuclear targets, in k+ nucleus scattering, and also in neutrino scattering on nuclear targets. In all these experiments, a sharp peak near 1540 MeV in the K0 proton or K+ neutron systems is observed, with width compatible with experimental resolutions. Here, I will present results of the study of the reaction gamma d arrow theta+ lambda. The data have been collected with the CEBAF Large Acceptance Spectrometet (CLAS) of Jefferson Laboratory. The produced lambda and theta+ baryons are detected through their decay channels into pi- protons and K+ neutron, respectively. The three charged particles are detected with CLAS, while the missing neutron is detected by using the missing mass technique. The theta+ signal is seen as a sharp peak in the mass of the k+ neutron system. Position and width of this peak are consistent with previous experimental measurements.
- Publication:
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APS April Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004APS..APRR15012M