The Θ + pentaquark baryon was searched for via the π -p→K -X reaction with a missing mass resolution of 1.4MeV/c2 (FWHM) at the Japan Proton Accelerator Research Complex (J-PARC). π - meson beams were incident on the liquid hydrogen target with a beam momentum of 1.92GeV/c. No peak structure corresponding to the Θ + mass was observed. The upper limit of the production cross section averaged over the scattering angle of 2° to 15° in the laboratory frame is obtained to be 0.26μb/sr in the mass region of 1.51-1.55GeV/c2. The upper limit of the Θ + decay width is obtained to be 0.72 and 3.1MeV for JΘP=1/2 + and JΘP=1/2 -, respectively, using the effective Lagrangian approach.
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