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Register a new userNon-equilibrium Phase Transitions in Ultrarelativistic Nuclear Collisions
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Highly excited nuclear matter created in ultrarelativistic heavy-ion collisions possibly reaches the phase of quark deconfinement. It quickly cools down and hadronises. We explain that the process of hadronisation may likely be connected with disintegration into fragments. Observable signals of such a scenario are proposed.
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We describe a model of jet quenching in nuclear collisions at RHIC energies. In the model, jet quenching is to be caused by the interruption of jet formation by nucleons arriving at the position of jet formation in a time shorter than the jet formation time. Our mechanism predicts suppression of high-pt spectra also in d+Au reactions.
The published theoretical data of few models (PHSD/HSD both with and without chiral symmetry restoration) applied to experimental data from collisions of nuclei from SIS to LHC energies, have been analised by using of the meta-analysis what allowed to localize a possible phase singularities of nuclear matter created in the central nucleus-nucleus collisions: The ignition of the Quark-Gluon Plasmas (QGP) drop begins already at top SIS/BEVALAC energies. This drop of QGP occupies small part, 15$%$ (an averaged radius about 5.3 fm if radius of fireball is 10 fm), of the whole volume of a fireball created at top SIS energies. The drop of exotic matter goes through a split transition (separated boundaries of sharp (1-st order) crossover and chiral symmetry restoration) between QGP and Quarkyonic matter at energy around $sqrt{s_{NN}},=,$3.5 GeV. The boundary of transition between Quarkyonic and Hadronic matter was localized between $sqrt{s_{NN}},=,$4.4 and 5.3 GeV and it is not being intersected by the phase trajectory of that drop. Critical endpoint has been localized at around $sqrt{s_{NN}},=,$9.3 GeV and a triple point - at around 12 GeV, the boundary of smooth (2-nd order) crossover transition with chiral symmetry restoration between Quarkyonic matter and QGP was localized between $sqrt{s_{NN}},=,$9.3 and 12 GeV. The phase trajectory of a hadronic corona, enveloping the drop, stays always in the hadronic phase.
The spinodal amplification of density fluctuations is treated perturbatively within dissipative fluid dynamics for the purpose of elucidating the prospects for this mechanism to cause a phase separation to occur during a relativistic nuclear collision. The present study includes not only viscosity but also heat conduction (whose effect on the growth rates is of comparable magnitude but opposite), as well as a gradient term in the local pressure, and the corresponding dispersion relation for collective modes in bulk matter is derived from relativistic fluid dynamics. A suitable two-phase equation of state is obtained by interpolation between a hadronic gas and a quark-gluon plasma, while the transport coefficients are approximated by simple parametrizations that are suitable at any degree of net baryon density. We calculate the degree of spinodal amplification occurring along specific dynamical phase trajectories characteristic of nuclear collision at various energies. The results bring out the important fact that the prospects for spinodal phase separation to occur can be greatly enhanced by careful tuning of the collision energy to ensure that the thermodynamic conditions associated with the maximum compression lie inside the region of spinodal instability.
The relativistic mean-field framework, extended to include correlations related to restoration of broken symmetries and to fluctuations of the quadrupole deformation, is applied to a study of shape transitions in Nd isotopes. It is demonstrated that the microscopic self-consistent approach, based on global effective interactions, can describe not only general features of transitions between spherical and deformed nuclei, but also the singular properties of excitation spectra and transition rates at the critical point of quantum shape phase transition.
The interplay of charmonium production and suppression in In+In and Pb+Pb reactions at 158 AGeV and in Au+Au reactions at sqrt(s)=200 GeV is investigated with the HSD transport approach within the `hadronic comover model and the `QGP melting scenario. The results for the J/Psi suppression and the Psi to J/Psi ratio are compared to the recent data of the NA50, NA60, and PHENIX Collaborations. We find that, at 158 AGeV, the comover absorption model performs better than the scenario of abrupt threshold melting. However, neither interaction with hadrons alone nor simple color screening satisfactory describes the data at sqrt(s)=200 GeV. A deconfined phase is clearly reached at RHIC, but a theory having the relevant degrees of freedom in this regime (strongly interacting quarks/gluons) is needed to study its transport properties.
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