Search for the Pentaquark ‘+ via the ”p ‘ K’X Reaction at J-PARCThis 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.Read More ISBN: 9789811000102, 9811000107
