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 (Cnp,nn) at small relative momenta on the stiffness factor γ of the symmetry potential energy is found: when γ 0.8, Cnp,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. density dependence of the symmetry energy, sensitive observables, HBT correlation In recent years, the isospin dependent equation of state (EoS) of both infinite and finite nuclear matter has been investigated in a deeper and broader range. Theoretically, a large amount of probes have been brought out to be sensitively affected by the isovector part of the EoS, i.e., the symmetry energy term. Based on different theories, the symmetry energy has been parameterized in different ways (please see refs. [1 − 3] for details). Among these parametrizations, E sym = S 0 u γ is often used (S 0 being the symmetry energy at the normal density, and u = ρ/ρ 0 the reduced density, while γ is the stiffness factor of the density dependence of the symmetry energy). Especially, the density dependence of the symmetry potential energy is paid much more attention since the uncertainty of the symmetry energy mainly comes from this term. Recently, with some comparisons between the results of experimental data and dynamical model IBUU, the uncertainty in the density dependence of the symmetry energy at subnormal densities is reduced into the range of γ ∼ 0.7 − 1.1, depending on the probable medium modifications of the nucleon transport [4,5] . Nevertheless, recently a quite soft symmetry energy (the corresponding γ factor is only about 0.3) was implied experimentally at very low nuclear densities (ρ N is 0.01 − 0.05 times normal density) [6] . Furthermore, in the most recent analyses by Tsang's group [7] , although they found that several different observables can provide consistent constraints on the density dependence of the symmetry energy, the constraints are still

Shannon information entropy in heavy-ion collisions

“…For the QMD-type models [83,87,88,89,90,91,92,93,94,95,96], the initial configurations of nuclei, which are obtained from initialization simulations, are selected when the similar binding energies and charge radii to the experimental data are obtained. Sometimes, a minimum distance between two arbitrary nucleons is required to give a more uniform initial phase-space distribution.…”

Energy dependence of the nucleus-nucleus potential and the friction parameter in fusion reactions

“…Like in the original QMD model [30] and in various modern versions of QMD models [47][48][49][50][51][52][53][54], a trial wave function for a nucleus in the ImQMD model [55][56][57][58][59] is restricted within a parameter space {r j , p j }, where r j and p j are mean values of position and momentum operators of the jth nucleon expressed by a Gaussian wave packet, and the total wave function is a direct product of these wave functions of Gaussian form. With the aid of a Wigner transformation, a nucleus composed of distinguishable N nucleons is characterized by the following one-body phase space distribution function,…”

Recent progress in theoretical nuclear physics related to large-scale scientific facilities

“…Based on the updated UrQMD transport model [22], the effect of the symmetry potential energy on the two-nucleon Hanbury-Brown-Twiss (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 [23]. 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.…”

“…The direct proton capture and resonance proton capture properties of stellar reactions 22 Mg(p,γ) 23 Al and 26 Si(p,γ) 27 P are studied by employing a mean-field potential obtained from the Skyrme-Hartree-Fock (SHF) model [37]. Calculations with the SHF potential reproduce well the looselybound structure of the ground states as well as the widths of the resonant states in these nuclei.…”

“…Calculations with the SHF potential reproduce well the looselybound structure of the ground states as well as the widths of the resonant states in these nuclei. With the obtained potential the reaction rates of direct proton capture and resonance proton capture to nuclei 23 Al and 27 P are estimated. The effect of the 27 P loosely-bound structure on the S factor of the direct proton capture is also discussed.…”