The existence of exotic hadrons not allowed by a naive qqq and qq¯ quark model would provide an opportunity to study the strong reaction in rare form. The pentaquark state named Θ +, with minimal constituent quark content uudds¯, has been predicted with a low mass of 1530 MeV/c2 and width no larger than 15 MeV/c2. Numerous experiments have since reported evidence of the Θ+ in both nK+ and pK 0 decay modes with the predicted characteristics, but the world's data is inconclusive due to limited statistics and background understanding. In this study, quasi-free photoproduction off a neutron in the reaction γ d → pp[special characters omitted]K– is exclusively measured using the CLAS detector system at Thomas Jefferson National Accelerator Facility. Tagged photons with energies from 1.6 to 3.6 GeV are measured in concidence with pπ+π– K– in the spectrometer. A multidimensional model based on Breit-Wigner distributions for the known background resonances is fit to the data with an unbinned likelihood method. No significant evidence of Θ+ production is found. An upper limit on the integrated total cross section of γn → Θ +K– is estimated at 3.3 nb with 95% confidence level.
|Advisor:||Tedeschi, David J.|
|Commitee:||Gothe, Ralf, Kubodera, Kuniharu, Valtorta, Marco|
|School:||University of South Carolina|
|School Location:||United States -- South Carolina|
|Source:||DAI-B 70/04, Dissertation Abstracts International|
|Subjects:||Particle physics, Nuclear physics|
|Keywords:||Exotic hadrons, Kaons, Pentaquarks, Photoproduction|
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