Effects Of Symmetry Energy In ¹³²Sn + ¹²⁴Sn Reaction At 300 MeV/nucleon

The state of equation of a nuclear matter is an important issue in nuclear physics.The EOS of the symmetry matter that has the same neutron and proton number has been studied by the nucleon collision experiments with GMR,elliptic flows and production of kaon.On the other side,we have few knowledge of the asymmetry nuclear matter that has different neutron and proton number.Symmetry energy of a nuclear matter is defined as the difference of the pure neutron matter and the symmetry matter.Knowledge on the density dependence of nuclear symmetry energy is important for understanding not only the structure of radioactive nuclei but also many important issues in nuclear astrophysics.Although the nuclear symmetry energy at normal nuclear matter density is known to be around 30 MeV from the empirical liquid-drop mass formula,its values at other densities are poorly known.Studies based on either microscopic many-body theories or phenomenological approaches have so far given widely divergent predictions on the density dependence of nuclear symmetry energy.Based on the recently updated isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU)transport model,we studied the effects of symmetry energy on the neutron to proton ratio n/p and the?/?-(10)ratio in the central 132Sn+ 124 Sn reaction at 300 MeV/nucleon.It is found that the n/ p ratio and the ?/ ?-(10)ratio in the central 132Sn+ 124 Sn reaction at 300 MeV/nucleon mainly probe the symmetry energy in the density region 1-1.5 times saturation density.However,the?/ ?-(10)ratio may be able to probe the density-dependent symmetry energy above 1.5 times saturation density by making some kinematic restrictions such as the azimuthal angle and kinetic energy cuts of emitting pions.