After collisions with impinging particle, a density fluctuation of nuclear matter may turn into a multibaryon (MB) with chiral symmetry restored in its interior. This method of observation of the chiral phase transition has its advantages due to a relatively moderate number of secondary particles to be measured. We suggest to use a cumulative particle as a trigger for a detection of MB decay products. Estimations show that its appearance is a signature of "deep cooling" of MB, which brings it close to the unexcited state. This gives a chance to separate MB from the secondary particle background. For separation of events with MB production, a role of intranuclear collisions of MB decay products should also be evaluated. We study experimental data taken with the EVA spectrometer at BNL as a simplified form of the problem. Analysis of intranuclear interactions before and after hard scattering of protons from SRC leads to a plausible conclusion that there were π-mesons missed in the experiment. Other logically permissible possibilities such as a color anti-transparency effect and a presence of states reminding a fusiform (ellipsoidal) body in the wave function of 12 C are briefly discussed too. Then we show that the short range correlation mechanism is not the only reasonable explanation of the experimental data. Interpretations based on dibaryons pre-existent in nuclei before its interaction with the projectile, or created during this interaction are also possible. Some examples of detection of MB production by the cumulative particle method are given with estimations of their feasibility.

A simple condition of deep cooling for observation of phase transitions in compressed fewnucleon systems was recently proposed. Here we have checked it using data obtained in the first physical experiment with accelerated nuclei at JINR synchrophasotron. Our study was inspired by a remark made by A.M. Baldin et al that one of peaks in observed double differential crosssection may arise due to an "excited state of deuterium nucleus". We have established that one of the peaks in the cross-section corresponds indeed to the dibaryon reported by WASA-at-COSY Collaboration. Another peak in the same region may be explained by interference of several usual baryon resonances. Even a more amazing fact has been established in a kinematical regions which were considered till now as a contribution of elastic deuteron-deuteron and nucleon(inside deuteron)-deuteron scattering. More careful calculations have shown that it is not the case. Trying to understand the nature of these peaks we looked over many dibaryons reported by different experimental groups and found that they may be excellently explained in terms of light dibaryons with equidistant mass spectrum observed by Yu.A. Troyan in a very different experiment. A natural explanation of these dibaryons may be given on basis of generalized coherent states discovered by A. Perelomov. These light dibaryons can be an experimental evidence for the pion Bose-Einstein condensate appearance in compressed and cooled nucleon systems. The condensate emerges due to a nonperturbative effect described by Bogoliubov's transformation which produces a pion state beyond the range of the Fock space. It should be also noted that this state of pion field has a mathematical and physical prototype in quantum optics, known there as the squeezed vacuum. Further experimental studies based on modern experimental facilities and more abundant statistics are necessary to verify our conclusions. September 15-20, 2014 JINR, Dubna, Russia * Speaker. . The dashed and dotted curves correspond to approximations of the first two peaks by the Gaussian functions which maxima positions are given in the insertion. XXII International Baldin Seminar on High Energy Physics Problems

No abstract