Search for the pentaquark at J-PARC

Abstract We have been searching for the Θ + pentaquark via the π − p → K − X reaction at the J-PARC hadron facility. No peak structure was observed in the missing mass spectrum obtained at 1.92 GeV / c beam momentum. The upper limit for the production cross section averaged over the scattering angle from 2° to 15° in the laboratory frame was derived to be 0.26 μb / sr . In order to make a more stringent constraint we have also performed a measurement at 2.0 GeV / c . Present analysis status of this new data is reported.