Pion production near absolute threshold, narrow resonances in (p, π) reaction and localized Δ-isobar states in nuclei

Possible mechanism of Δ-isobar localized state formation in nuclear reaction is considered. A set of main Δ-isobar localized state characteristics is obtained and the model of π, γ-production in p-nucleus and nucleus-nucleus collisions through Δ-localized state formation is suggested. The results of the calculations show that the theory successfully explains the characteristics of narrow resonance (Ep = 350 MeV, Γ < 10 MeV), observed recently in proton-nucleus collisions as well as the effect of stability of the pion spectra slope parameter near the absolute threshold. The experiments for checking the outlined theoretical approach are suggested. (orig.)