Heavy ion collisions at high energies provide a unique opportunity to study the nuclear matter under extreme density and temperature. These extreme conditions are well suited to the investigation of the compressibility of the nuclear matter, in particular, the stiffness of the nuclear equation-of-state (EOS). The theoretical models suggest different possible scenarios for these modifications, so that new experimental data with high resolution and statistics are needed in order to disentangle the different theoretical predictions. The research program on heavy-ion collisions at the Nuclotron of the Joint Institute for Nuclear Research includes investigation of the reaction dynamics and nuclear EOS, study of the in-medium properties of hadrons, production of (multi)-strange hyperons at the threshold and search for hyper-nuclei.
The figure 2 presents the three-dimensional scheme of the MPD facility. It proposed to explore phase diagram of strongly interacting matter in a high track multiplicity environment has to cover a large phase space, be functional at high interaction rates and comprise high efficiency and excellent particle identification capabilities.
The NICA/MPD detector combining the large phase space coverage and excellent PID. capabilities offer the exciting possibility to study in great detail transverse mass (mt) and rapidity (y) dependence of hadron production. Detailed measurements of the excitation of the effective temperature of the kaon spectra in different colliding systems (from p+p to central A+A) may help to identify a possible phase transition.
One of the main goals of the experiments on heavy ion beams is to discover and study a new form of QCD matter, the quark-gluon plasma (QGP) In recent years advances in theory led to a significant complication of the QCD phase diagram, in particular, to the appearance of a critical point. The discovery of critical point at intermediate temperature and density is considered as one of the most important goals of FAIR and NICA projects. The region of low temperature and extreme baryon density is considered as hardly achievable in laboratory conditions, whereas it is probably realized in nature, in neutron stars. At high density and low temperature the first order phase transition and existence of color superconductivity phase are expected.