Formation of 24Mg* in the Splitting of 28Si Nuclei by 1-GeV Protons

The 28 Si(p,p ′ γ 0 X) 24 Mg reaction has been studied at the ITEP accelerator by the hadron-gamma coincidence method for a proton energy of 1 GeV. Two reaction products are detected: a 1368.6-keV γ -ray photon accompanying the transition of the 24 Mg ∗ nucleus from the first excited state to the ground state and a proton p ′ whose momentum is measured in a magnetic spectrometer. The measured distribution in the energy lost by the proton in interaction is attributed to five processes: the direct knockout of a nuclear α cluster, the knockout of four nucleons with a total charge number of 2, the formation of the ∆ Si isobaric nucleus, the formation of the ∆ isobar in the interaction of the incident proton with a nuclear nucleon, and the production of a π meson, which is at rest in the nuclear reference frame. The last process likely corresponds to the reaction of the formation of a deeply bound pion state in the 28 P nucleus. Such states were previously observed only on heavy nuclei. The cross sections for the listed processes have been estimated.