Inclusive spectrum of the reaction at 1.69 GeV/

Ichikawa, Yudai   ; Hasegawa, Shoichi   ; Hosomi, Kenji  ; Imai, Kenichi; Sako, Hiroyuki   ; Sato, Susumu  ; Sugimura, Hitoshi; 37 of others*

We have measured an inclusive missing-mass spectrum of the reaction at the pion incident momentum of 1.69 GeV/ at the laboratory scattering angles between 2 and 16 with the missing-mass resolution of 2.7 0.1 MeV/ (FWHM) at the missing mass of 2.27 GeV/. While gross spectrum structures are well understood in the simple quasi-free picture, we have observed two distinct deviations; one peculiar enhancement at2.13 GeV/ is due to the cusp, and the other notable feature is a shift of a broad bump structure, mainly originating from hyperon resonance productions of and , by about 22.4 0.4 (stat.) (syst.) MeV/ toward the low-mass side, which is calculated in the kinematics of a proton at rest as the target.