The K1.8BR and K1.8 beam lines at the J-PARC Hadron Experimental Facility provide intense secondary kaon beams in the momentum region of approximately 0.6–2 GeV/c, offering unique opportunities to study strange-hadron spectroscopy and hadron interactions. At K1.8BR, the E72 experiment investigates the $K^-p$ reaction near the $\Lambda\eta$ threshold to clarify the threshold enhancement and...
The Λη threshold region is of particular interest for understanding the excitation spectrum of Λ hyperons. Previous measurements of the K−p → Λη reaction revealed a strongly non-uniform angular distribution near threshold. Since a J/P = 1/2− resonance is expected to produce a nearly isotropic angular distribution in this region, the observed behavior cannot be readily explained by the...
