Difficulties in probing density dependent symmetry potential with the HBT interferometry

Abstract

Based on the updated UrQMD transport model, the effect of the symmetry potential energy on the two-nucleon HBT correlation is investigated with the help of the coalescence program for constructing clusters, and the CRAB analyzing program of the two-particle HBT correlation. An obvious nonlinear dependence of the neutron-proton (or neutron-neutron) HBT correlation function (C np,nn ) at small relative momenta on the stiffness factor γ of the symmetry potential energy is found: when γ ≲ 0.8, C np,nn increases rapidly with increasing γ, while it starts to saturate if γ ≳0.8. It is also found that both the symmetry potential energy at low densities and the conditions of constructing clusters at the late stage of the whole process influence the two-nucleon HBT correlation with the same power.