Resonance search on πN reaction

Present status of the study on resonance state is reviewed. Among various problems on the resonance state, the inelastic decay of baryon resonance and boson resonance are described in this paper. Experimental data on N → N eta with bubble chambers are few. An experimental results by using a counter shows enhancement around 1.8 GeV in the relation between cross section and energy. Some bubble chamber experiment also shows enhancement around 1.6 GeV. The spin and parity analyses for 1000 events are required. Data on N → Nω show enhancement at 1.76 GeV. The effective mass distribution on N → delta++ (1236)π+π- shows enhancement around 2.0 GeV. Study on the boson resonance has been made, but still ambiguity remains. Effective mass distribution on the reaction π+d → pspπ+π-π0 shows a peak of ω1664. The assignment of spin and parity by Matthews et al. is not in agreement with that by Kenyon et al. therefore confirmation by other experiment is necessary. A few experiment show peaks at 1.4 and 1.7 GeV in the effective mass distribution of (rho0rho0) in the reaction anti pp → 3π+π-. Confirmation is also required. Deviation was found in the effective mass distribution of (ωπ+π-) in anti pp → 3π+π-π0 reaction, and ωπ+π- decay was seen in π+d → psp2π+2π-π0 reaction. (Kato, T.)