Measurement of cumulative-photon spectra at high transverse momenta in 12 C 9 Be interactions at an energy of 3.2 GeV pe
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CLEI Experiment
Measurement of Cumulative-Photon Spectra at High Transverse Momenta in 12 C9Bе Interactions at an Energy of 3.2 GeV per Nucleon I. G. Alekseev, V. E. Vishnyakov, A. I. Golutvin, V. S. Goryachev, G. B. Dzubenko, A. G. Dolgolenko, B. V. Zagreev, S. M. Kiselev, I. E. Korolko, G. A. Leksin, K. R. Mikhaylov, P. A. Polozov, M. S. Prokudin, D. N. Svirida, A. V. Stavinsky, V. L. Stolin, and G. B. Sharkov Institute of Theoretical and Experimental Physics, Bol’shaya Cheremushkinskaya ul. 25, Moscow, 117289 Russia Received February 20, 2008; in final form, May 30, 2008
Abstract—For 12 C9 Bе interactions at a kinetic beam energy of 3.2 GeV per nucleon, the spectra of photons at laboratory angles in the range 55◦ –73◦ were measured off the kinematical region available to the interaction of single nucleons within colliding nuclei. The use of a fast trigger for selecting events involving the production of high-transverse-momentum photons made it possible to measure spectra off the kinematical boundary of four-nucleon interaction. It is shown that the proposed procedure is adequate to the problem of searches for and investigation of flucton–flucton interaction. In the kinematical region where flucton–flucton interaction can manifest itself, the cross sections in question are on the same order of magnitude as respective model predictions. In order to draw definitive conclusions on the role of flucton– flucton interaction, it is highly desirable to extend the angular range of the measurements toward smaller angles. PACS numbers: 21.65.Qr, 24.80.+y, 25.75.Gz DOI: 10.1134/S1063778808110033
INTRODUCTION Investigation of nuclear matter at high density or high temperature (or at both high density and high temperature) is one of the fundamental problems in relativistic nuclear physics. Considerable advances have recently been made in theoretically studying the phase diagram of nuclear matter. New states of nuclear matter are expected not only in the region of high temperatures (quark–gluon plasma [1]) but also in the region of low temperatures and high densities (color superconductivity [2]). The question of how one can create such unusual conditions in laboratory experiments has still remained open. Our idea is to develop a trigger that would select extremely rare events in which final states characterized by a very high baryon density may arise even at moderate energies of colliding nuclei. We believe that a cumulative effect [3], which manifests itself, in particular, in the formation of particles in a kinematical region forbidden for free nucleon–nucleon (N N ) interaction, conceals a potential for creating an efficient trigger. The cumulative effect, which was discovered experimentally in studies performed at the Institute of Theoretical and Experimental Physics (ITEP,
Moscow) and the Joint Institute for Nuclear Research (JINR, Dubna) [4], is considered as a signature of an interaction where at least one of the participants is a dense multinucleon (multiquark) nuclear-matter fluctuation (flucton) [5]. Yet another model of cumulative
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