Study of polarization effects at Nuclotron

Abstract

Abstract. The major goal of the upgraded Nuclotron facility is to obtain the information on the equation-of-state for dense nuclear matter playing a key role in the under standing of the collapse supernovae and neutron stars stability. These studies can be performed either in heavy ion collisions or via the short-range few nucleon correlations. The obtained experimental results and future program with the use of polarized deuteron beam and the internal target station are discussed. The polarization studies for the NN, NA and dA reactions with the extracted deuteron beam at the BM@N setup are proposed. The further extension of the polarization program at BM@N is related with the study of the in-medium modification of the polarization for the strange and multi-strange baryons and the spin alignment for vector mesons decaying in hadronic modes. IntroductionThe Nuclotron at JINR will provide beams of heavy ions with energies up to 6 A·GeV for isospin symmetric nuclei, and 4.65 A·GeV for Au nuclei. In central heavy-ion collisions at these energies, nuclear densities of about 4 times nuclear matter density can be reached. These conditions are well suited to investigate the equation-of-state (EOS) of dense nuclear matter which plays a central role for the dynamics of core collapse supernovae and for the stability of neutron stars. The observation of multi-strange hyperons or of light hypernuclei at Nuclotron energies would represent a breakthrough in our understanding of strange matter, and would pave the road for the experimental exploration of the 3-rd dimension of the nuclear chart [1]. These studies are complimentary to the CBM experimental program at SIS100 [2]. Another tool to investigate the EOS at large densities is the study of the short range correlations (SRC) of nucleons in nuclei which is the subject of intensive theoretical and experimental works during last years. Since SRC have densities comparable to the density in the center of a nucleon which is about ρ ∼ 5ρ 0 (ρ 0 ≈ 0.17 fm −3 ), they can be considered as the drops of cold dense nuclear matter [3]. These studies explore a new part of the phase diagram and very essential to understand the evolution of neutron stars.The results obtained at BNL [4], SLAC [5] and JLAB [6,7] clearly demonstrate that more than 90% all nucleons with momenta k ≥ 300 MeV/c belong to 2N SRC; the probability for a given proton with momenta 300 ≤ k ≤ 600 MeV/c to belong to pn correlation is ∼18 times larger than for pp correlations; the probability for a nucleon to have momentum ≥ 300 MeV/c in medium nuclei is ∼25%; 3N SRC are present in nuclei with a significant probability [8]. However, still many open questions persist and further investigations are required both from the