vbid/9789811000126

Description

This theses reports on an experimental search for an exotic hadron, ?+(1540) pentaquark, which is a genuine exotic hadron with a five-quark system of uuddsbar.�The results of this book support that the existence of ?+�was strongly constrained.� The ?+�pentaquark was searched for via the �-�p�?�K-�X reaction using a beam momentum of 2.01 GeV/c at the J-PARC hadron experimental facility, taking advantage of high-statistics and high-resolution compared with previous experiments, some of which claimed the evidence of ?+. In order to realize a good missing-mass resolution of 2 MeV, the beam spectrometer and superconducting kaon spectrometer were constructed. No clear peak was observed in the missing mass spectrum of the �-�p�?�K-�X reaction, and the upper limit of the production cross section was found to be less than 0.28�?b/sr at the 90% confidence level in a mass region of 1500�1560 MeV/c2. This upper limit is an order of magnitude smaller than that of the previous KEK experiment. Compared with a theoretical calculation using the effective Lagrangian approach, the decay width of ?+�was evaluated. The upper limits on the decay width were estimated to be 0.36 and 1.9 MeV for the ?+�spin-parity of 1/2+�and 1/2-, respectively. These are quite small for a width of ordinary hadron resonances, and the existence of ?+�was strongly constrained and is doubtful.Typham this is the title: Search for the Pentaquark ?+ via the �?p ? K?X Reaction at J-PARC