From soft photon study at Nuclotron and U-70 to NICA

Experimental and theoretical studies of direct photon production in hadronic collisions essentially expand our insights in multiparticle production mechanisms. These photons are useful probes to investigate nuclear matter at all stages of the interaction. Soft photons play a particular role in these studies. Until now we have no explanation for the experimentally observed excess of soft photons. These photons have low transverse momenta $p_{T} < 0.1$ GeV/c, $\vert x\vert < 0.01$ . In this domain their yield exceeds the theoretical estimates by 5-8 times. The registration of soft photons at Nuclotron (LHEP, JINR) has been carried out by the electromagnetic calorimeter built by the SVD-2 Collaboration. Soft photon electromagnetic calorimeter was tested at U-70, IHEP (Protvino). For the first time the soft photon yield at interactions of 3.5A GeV/c per nucleon deuterium and lithium beams has been measured. The obtained energy spectra confirm the increased yield of soft photons with their energy less than 50MeV (in the laboratory system) in comparison with theoretical predictions and agree with previous experiments at high-energy interactions. It is planned to continue soft photon study at the future accelerator complex NICA with heavy-ion beams

Proceedings of the XLIII International Symposium on Multiparticle Dynamics

The E190 Experiment is aimed at the search for collective phenomena in a quark-gluon system and a hadron system. It is carried out at U-70 in IHEP, Protvino. The evidence of Bose-Einstein condensation of pions has been confirmed with a twofold increasing of sampling at a level of 7 standard deviations. We study soft photon (smaller than 60 MeV) yield by using of an electromagnetic calorimeter with low energy threshold. In the gluon dominance model we explain multiparticle production by the active gluons. In this model the estimation of the contribution of charge exchange has been obtained.Sponsorship: IIT College of Science, High Energy Physics Division of Argonne National Laborator