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The yield of the O(γ, π p) reaction has been measured in the region of the excitation of the Δ(1232) isobar at high momentum transfers to the residual nuclear system. The experimental data are interpreted within the model taking into account manifestations of isobar configurations in the ground state of the O nucleus. Direct and exchange mechanisms of the production of pions with emission of one and two nucleons, which follow from the structures of the density matrices for these reactions, have been considered. The probability of the production of the Δ-isobar in the ground state of the O nucleus has been empirically estimated as P = 0.019 ± 0.003 ± 0.003. [ABSTRACT FROM AUTHOR]

The 28Si( p, p′γ0 X)24Mg 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 24Mg* 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 ΔSi isobaric nucleus, the formation of the Δ 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 28P nucleus. Such states were previously observed only on heavy nuclei. The cross sections for the listed processes have been estimated. [ABSTRACT FROM AUTHOR]

The cross section for the [sup 12]C(γ,π[sup +]p) reaction was measured in the range of the Δ(1232) isobar. The data were analyzed using the models taking into account the nucleon and isobaric degrees of freedom of the [sup 12]C nucleus. The conclusion is drawn that in the large-momentum transfer range the π[sup +]p pairs are produced in the course of the direct knocking-out of Δ[sup ++] isobar from the nucleus. The probability of finding the Δ isobar in the ground-state [sup 12]C nucleus is estimated at 0.018±0.005Δ isobars per nucleon. © 2001 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Results from the Spherical Nonmagnetic Detector (SND) on Δ(1232) isobar electroproduction in the collisions of beam electrons (positrons) and residual gas nuclei in the VEPP-2M e[sup +]e[sup -] collider are presented. On the basis of the data obtained the expected counting rate of this process in future high-luminosity e[sup +]e[sup -] colliders (φ, c-τ, and b factories) is estimated. [ABSTRACT FROM AUTHOR]