STUDY OF ISOBAR FORMATION IN CENTRAL INTERACTIONS AT 20.8 GeV/C

Abstract

This work is devoted to the study of the formation of isobars in the interactions of protons with the nuclei of a photoemulsion irradiated with protons with a pulse of 20.8 GeV/s. Events with at least two relativistic particles ejecting at an angle of less than 170 were selected for research. At the same time, the presence of highly ionizing particles with a number of at least 8 was required. Pulse and ionization measurements were carried out on the traces of highly ionizing particles. The method of selecting рπ± stars is described. For stars in which the proton was accurately identified, 472 pπ+ and 340 pπ--pairs were collected. It was assumed that the leading Δ++(1232)-isobar could form in the identified pπ+-pairs, and the leading Δ°(1232)-isobar could form in the pπ--pairs. In the mass distribution of the pπ+ events, a significant excess over the background was observed in the range of 1.12 < M < 1.4 GeV. The cross-section for the formation of Δ++(1232)-isobars is ϭΔ++ = 79 ± 26 mbn. In the distribution of events by Mpπ-, the excess of events over the background was less significant, and the cross-section for the formation of the leading Δ°(1232) isobar was found to be ϭΔ° = 65 ± 51 mbn. Based on the data on the formation of Δ++- and Δ°-isobars in central pAgBr-collisions at 20.8 GeV/c, it was concluded that most of the leading protons in such collisions are formed through the decay of isobars.