Speaker
Description
The J-PARC E72 experiment investigates the K⁻p → Λη reaction near the Λη threshold using a 0.735 GeV/c K⁻ beam at the K1.8BR beam line. The Λη threshold region is of particular interest for studying excited Λ hyperons and threshold dynamics. Previous measurements showed a strongly non-uniform angular distribution near threshold, which cannot be readily explained by the established Λ(1670) state alone. This has motivated further studies of possible resonance contributions and cusp structures in the Λη channel.
Physics data taking for the E72 experiment started in 2025. In this contribution, we will report preliminary results from the ongoing analysis. The analysis focuses on the Λη cusp structure and possible contributions from excited Λ states near threshold, including a spin-3/2 candidate. The current status of event reconstruction, acceptance studies, and angular-distribution analysis will be discussed.
Related hadron-beam programs and future prospects at the K1.8 beam line will also be briefly introduced.