Search for collective phenomena in high multiplicity events at Nuclotron and U-70

Abstract

More than ten-year experimental search for collective phenomena in high multiplicity events has been carried out at the Laboratory of high energy physics at JINR. We present main results, which have been received at the U-70 accelerator (IHEP, Protvino) in the proton collisions and at Nuclotron ( JINR, Dubna) in the nuclear interactions. For 𝑝𝑝 interactions, topological cross sections have been gone three orders down and achieved KNO-scaling variable (𝑛/𝑛) 4.5. Probably, the tail of high multiplicity distribution stipulates gluon splitting. In the region of high multiplicity, the formation of pions is predominant. Some collective phenomena are predicted in this region. Using charged multiplicity data, we could restore total (sum of charged and neutral particles) multiplicity and have implemented unique research for fluctuations of the neutral particle number at the given total multiplicity. The revealed growth of scaled variance may indicate the pion (Bose-Einstein) condensate formation. The excess of soft photon yield at interactions of the Nuclotron beams (d, Li and C) with a carbon target has been confirmed. This can be connected with the pion condensate formation. Currently, we prepare two-shoulder electromagnetic calorimeter to carry out experimental studies at BM@N setup and plan to take part in new experiments on heavy ion collisions at Nuclotron.