Isobaric yield ratio difference between the140AMeVNi58+Be

Abstract

Background: The isobaric yield ratio difference (IBD) method is found to be sensitive to the density difference of neutron-rich nucleus induced reaction around the Fermi energy.Purpose: An investigation is performed to study the IBD results in the transport model. Methods:The antisymmetric molecular dynamics (AMD) model plus the sequential decay model GEMINI are adopted to simulate the 140A MeV 58,64 Ni + 9 Be reactions. A relative small coalescence radius Rc = 2.5 fm is used for the phase space at t = 500 fm/c to form the hot fragment. Two limitations on the impact parameter (b1 = 0 − 2 fm and b2 = 0 − 9 fm) are used to study the effect of central collisions in IBD.Results: The isobaric yield ratios (IYRs) for the large-A fragments are found to be suppressed in the symmetric reaction. The IBD results for fragments with neutron-excess I = 0 and 1 are obtained. A small difference is found in the IBDs with the b1 and b2 limitations in the AMD simulated reactions. The IBD with b1 and b2 are quite similar in the AMD + GEMINI simulated reactions. Conclusions:The IBDs for the I = 0 and 1 chains are mainly determined by the central collisions, which reflects the nuclear density in the core region of the reaction system. The increasing part of the IBD distribution is found due to the difference between the densities in the peripheral collisions of the reactions. The sequential decay process influences the IBD results. The AMD + GEMINI simulation can better reproduce the experimental IBDs than the AMD simulation.

Improved thermometer for intermediate-mass fragments in heavy-ion collisions with isobaric yield ratio difference

“…( 2) has been used to determine T [34,35]. In the IBD analysis, ∆µ/T from the small A fragment changes very little [45,[47][48][49][50][52][53][54], which means that ∆µ/T can be canceled out in the difference between the IYRs in Eqs. ( 2) and ( 3).…”

“…In the isoscaling or the IBD methods, the fragments in the two reactions are assumed to have the same temperature, which can make it possible to cancel out the free energy of the fragments [47,49,53] (in the recent Shannon information uncertainty method, this is not required [54]). Since T IB is obtained from fragments, it is interesting to check whether T IB is the same in the dif- ferent reactions.…”

“…Another question is that in thermodynamic models, temperature is incorporated in the probes for nuclear matter, such as nuclear symmetry energy, in heavy-ion collisions. For the many probes used to study the nuclear symmetry energy, such as the isoscaling method [37][38][39][40][41], the isobaric ratio method [26,[42][43][44][45][46], and the IYR difference (IBD) method [47][48][49][50][51][52][53][54], T is a part of the probe and cannot be separated easily. In the IYR method, the ratio of the symmetry-energy coefficient (a sym ) to T (a sym /T ) is instead used to study the symmetry coef-ficient of the neutron-rich nucleus [26,[42][43][44].…”

Mass dependence of temperature for intermediate mass fragment in heavy-ion reactions

“…Using different approximations of free energy for fragment, equation (2) has been used to determine T from IMFs [42,43]. It has been shown that in the IBD analysis m D T determined by the small-A fragment changes very little [33][34][35][36][37][38][39]50], indicating that m D T can be canceled out in the difference between the IYRs in equations (2) and (3). Defining the difference between IYRs in equations ( 2) and (3), one has,…”

“…Besides, the temperature is difficult to be separated from the probes to investigate the nuclear matters in HICs. For example, in the isoscaling method [26][27][28][29], the isobaric-yield-ratio (IYR) methods [21,[29][30][31][32] and the isobaric-yield-ratio-difference (IBD) method [33][34][35][36][37][38][39][40][41], the ratios of chemical potential to temperature entirely are taken as probes.…”