Search for penta-quark baryon at the J-PARC K1.8 beam line; First result and current status

Shirotori, Kotaro

An observation of the pentaquarck baryon which consists of five quarks was firstly reported by the LEPS collaboration in 2003. The LEPS report triggered the investigation of . Several experiments reported both positive and negative results. Therefore, the existence of has been not confirmed. The J-PARC E19 experiment was performed at the J-PARC K1.8 beam line in 2010. The purpose of experiment is to search for using the SKS system. The missing mass resolution of the system was 1.4 MeV/ (FWHM) by which the highest sensitivity can be achieved. We irradiated mesons on the liquid hydrogen target with the beam momentum of 1.92 GeV/. In the missing mass spectrum, any prominent structure corresponding to was not observed. The upper limit of the cross section was obtained to be less than 200 nb. The experimental result gives a strong constraint to the existence of .