On the production of cumulative protons in high-energy hadron-nucleus and nucleus-nucleus collisions
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TTERS TO THE EDITOR
On the Production of Cumulative Protons in High-Energy Hadron–Nucleus and Nucleus–Nucleus Collisions K. Olimov*, S. L. Lutpullaev, V. I. Petrov, E. Kh. Bazarov, and B. S. Yuldashev1) Institute for Physics and Technology, Fizika-Solutse Research and Production Association, Uzbek Academy of Sciences, ul. G. Mavlyanova 26, Tashkent, 700084 Republic of Uzbekistan Received April 4, 2007
PACS numbers: 25.10.+s DOI: 10.1134/S1063778807110191
Although experimental and theoretical studies of cumulative-particle production in high-energy hadron–nucleus collisions have been performed for more than 35 years, a consistent theory that would describe quantitatively various features of cumulative processes has yet to be developed. As far back as 1971, Baldin [1] examined a possible mechanism of such processes. According to his idea, the coalescence of two or more nucleons into a hadron drop of space dimension smaller than 1 fm is necessary for the formation of a cumulative particle emitted into the backward hemisphere with a high momentum. As a matter of fact, this idea, which was first confirmed in [2], was a development of Blokhintsev’s flucton hypothesis [3] proposed to explain experimental data on the proton yield in the backward direction and a large cross section for deuteron production in hadron–nucleus collisions. Naturally, the assumption considered first was that the production of the cumulative particles may be associated with the nucleon Fermi momenta. However, calculations that took into account the Fermi momentum [4] showed that it is impossible to describe, in this way, the high-momentum section of the cumulative-proton spectrum. According to [1], two mechanisms may be responsible for the appearance of dense quark bags. These are that of density fluctuations (fluctons) in normal nuclear matter (cold model) and that of nuclearmatter compression under the effect of a projectile particle (hot model). As was indicated in [5], it is still difficult to choose between these two models. It is important to note that local properties of hadron matter, which are independent of the space 1)
Institute of Nuclear Physics, Uzbek Academy of Sciences, pos. Ulugbek, Tashkent, 702132 Republic of Uzbekistan. * E-mail: [email protected]
extension of a nuclear medium having an approximately uniform density, may manifest themselves in cumulative processes. If the cumulative effect results from interaction with multiquark configurations in nuclei, scale invariance, manifesting itself in the collision-energy independence of invariant cross sections, which was confirmed experimentally, is a significant feature of such processes, as in elementaryparticle interactions. In [6], our group studied the production of cumulative protons in the high-energy collisions of π − mesons, protons, and light nuclei (4 Не and 12 С) with сarbon nuclei and showed that the average multiplicity of cumulative protons in such events is 1.05 ± 0.02 and is independent of the primary energy and the projectile type. This result is likely to suggest that the pi
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