Study of Λ identification method by the π⁻p → K⁰ Λ reaction for a Λp scattering experiment at J-PARC

The π⁻ p → K⁰Λ reaction is an important elementary process to produce Λ from a proton target and is a key for a Λp scattering experiment where the momentum of Λ should be tagged from the missing momentum of the (π⁻, K⁰) reaction. However, the (π⁻, K⁰) spectroscopy method has not been established yet due to the difficulty of the K⁰ detection. Therefore, we have proposed a new K⁰ detection method where π⁺ and π⁻ from the K⁰ decay are measured by a forward magnetic spectrometer and a detector cluster surrounding the target, respectively. The feasibility of the K⁰ detection method was confirmed by analyzing the J-PARC E40 data taken with such a detector system. In the analysis, Λ's were successfully identified in the missing mass spectrum of the π⁻ p → K⁰X reaction. (author)