The pentaquark Θ+ has been searched for via the π-p→K-X reaction with beam momenta of 1.92 and 2.01 GeV/c at J-PARC. A missing mass resolution of 2 MeV (FWHM) was achieved but no sharp peak structure was observed. The upper limits on the production cross section averaged over the scattering angle from 2 to 15in the laboratory frame were found to be less than 0.28 μb/sr at the 90% confidence level for both the 1.92- and 2.01-GeV/c data. The systematic uncertainty of the upper limits was controlled within 10%. Constraints on the Θ+ decay width were also evaluated with a theoretical calculation using an effective Lagrangian. The present result implies that the width should be less than 0.36 and 1.9 MeV for the spin-parity of 1/2+ and 1/2-, respectively.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics