Study The Properties Of Dense Nuclear Matter In Heavy-ion Collisions

The violent astronomical events in the universe,such as the explosion of supernova,the birth of neutron-star and black hole,astrophysical nucleosynthesis,the gravitational waves and the gamma-ray bursts,are related to the dense celestial body.The dense celestial body,except the most central and surface,is usually considered to be asymmetric high-density nuclear matter.Studying the properties of asymmetric highdensity nuclear matter,such as the equation of state(EOS),will not only provide crucial information about the dense star and the evolution of the high-temperature quark gluon plasma(QGP)produced the Big Bang,but will afford unique information about novel nonperturbative aspects of quantum chromodynamics(QCD).The nuclear symmetry energy,which describes the energy difference of per proton and neutron in nuclear matter,has been extensively studied within the last two decades.Around saturation density,both the value and the slope of the nuclear symmetry energy have been roughly constrained,its high-density behavior is now still in argument.By involving the constraints of the slope of nuclear symmetry energy L into the question of determination of the high-density symmetry energy,one needs to probe the curvature of nuclear symmetry energy Ksym.Based on the isospin-dependent Boltzmann-UehlingUhlenbeck transport model,effects of the curvature of nuclear symmetry energy on the squeezed-out nucleons are demonstrated in the semicentral Au+Au reaction at 400 and 600 Me V/nucleon.It is shown that the squeezed-out isospin-dependent nucleon emissions at high transverse momenta are sensitive to the curvature of nuclear symmetry energy.And the isotope Sn+Sn reactions at 270 Me V/nucleon are investigated.It is shown that nucleon and meson observables in the Sn+Sn reactions at 270 Me V/nucleon cannot effectively probe the high-density symmetry energy.These observables,however,are sensitive to the curvature of the symmetry energy.Based on the relativistic transport model ART with the hadronic equation of state extended to have a phase transition via the use of the MIT bag model,properties of phase transition of dense nuclear matter formed in relativistic heavy-ion collisions are investigated.Proton sideward and directed flows are calculated with different equation of states in Au +Au collisions at beam energies of 2,4,6 and 8 Ge V/nucleon.Compared with AGS experimental data in existence,the boundary of first-order phase transition is roughly confined,i.e.,in the range of 2.5-4 times saturation density with temperature about 64-94 Me V.Such constraints are useful for ongoing RHIC Beam Energy Scan-II program to study the QCD matter phase diagram.