Neutron-skin effects in isobaric yield ratios for mirror nuclei in a statistical abrasion-ablation model

Abstract

Background: The isobaric yield ratio for mirror nuclei [IYR(m)] in heavy-ion collisions, which is assumed to depend linearly on x = 2(Z − 1)/A 1/3 of a fragment, is applied to study some coefficients of the energy terms in the binding energy, as well as the difference between the chemical potentials of a neutron and proton. It is found that the IYR(m) has a systematic dependence on the reaction, which has been explained as the volume and/or the isospin effects in previous studies. However, neither the volume nor the isospin effects can fully interpret the data.Purpose: We suppose that the IYR(m) depends on the neutron-skin thickness (δnp) of the projectile, and check the idea of whether the neutron-skin thickness effects can fully explain the systematic dependence of the IYR(m).Methods: A modified statistical abrasion-ablation model is used to calculate the reactions induced by projectiles of three series: (1) the calcium isotopes from 36 Ca to 56 Ca as projectiles with different limitations on the impact parameters (bmax) to show the volume effects according to bmax; (2) the A = 45 isobars as the projectiles having different isospins and δnp; and (3) projectiles having similar δnp to show whether the IYR(m) depends on the volume or the isospin of the projectile. Results:The IYR(m) shows a distribution of a linear part in the small-x fragments, and a nonlinear part in the large-x fragments. The linear part of IYR(m) is fitted. (1) In the calcium isotopic reactions, the IYR(m) depends on the isospin or the volume of the projectile, but δnp greatly influences the nonlinear part of the IYR(m). The IYR(m) does not depend on the colliding source in reactions of small bmax for the nonneutron-rich projectiles, and does not depend on the collision sources in reactions by the neutron-rich projectiles; (2) In reactions of the A = 45 isobars, though IYR(m) depends on the isospin of projectile, IYR(m) shows small dependence on isospin if δnp > 0; (3) In the reactions of projectiles having similar δnp, the IYR(m) in the small mass fragments show no dependence on the volume and the isospin of the projectile when the mass of the projectile is relatively large. Specially, the dependence of IYR(m) on the mass of the isospin of the projectile vanishes when δnp ∼ 0.02fm. Conclusions:The linear and nonlinear parts of the IYR(m) are governed by the core and the surface (skin) of the projectile, respectively. The neutron-skin effects can well explain the systematic dependence of the IYR(m).

Neutron density distributions of neutron-rich nuclei studied with the isobaric yield ratio difference

“…We have also explained the increasing ∆µ/T (or α − β) with A in a similar way by consider the central and peripheral collisions separately [17,18,26]. The fragments with small A are mainly produced in the central collisions which is almost not influenced by the neutron-skin, while the fragments having A near the projectile are governed by the neutron-skin [20,21,43,80]. The neutron-skin is also found to make the IYR increase nonlinearly [20,21].…”

“…Huang et al proposed the IYR method to determine the symmetry energy coefficients of the nearly symmetric fragments [8], and this IYR method was extended to the neutron-rich fragment to understand the evolution of symmetry-energy coefficient in neutron-rich nuclei [13,14,15]. The IYR method is further developed, and improvements have been achieved to understand the IYR results [16,17,18,19,20,21]. The results of the NSE in Refs.…”

Target effects in isobaric yield ratio differences between projectile fragmentation reactions

“…T he IBD probe can indicate the difference betw een the densities o f reactions induced by projectiles w ith different asym m etry [2][3][4][5], T he am ounts o f isotopes produced in the 140A M eV 48-40C a + 18IT a /9Be and ^" Ni + 181T a /9Be reactions have been m easured w ith high precision by M ocko et al at the N ational Superconducting C yclotron Laboratory (N SCL), M ichigan State U niversity [22]. These high quality data have been studied extensively for different purposes [2,8,9,15,16,[23][24][25][26][27][28] [8,9,29,30] or tem perature [23,24]. T he IBD results for the reactions w ith the 9Be target are know n to be sensitive to the density difference betw een the projectiles [2].…”

Determination of neutron-skin thickness using configurational information entropy

“…The projectile fragmentation reaction, which is the main experimental approach for studying rare isotopes, is suitable for determining the neutron skin thickness owing to the obvious experimental phenomena induced by the neutron skin structure [9,10]. For example, isospin effects in the isotopic cross section [11], neutron-abrasion cross section (σ nabr ) [12], neutron removal cross section [13], mirror nuclei ratio or isobaric ratio [14], and isoscaling parameter (α) [15]. Parityviolating electron scattering (PVS) is the only method used to determine neutron skin thickness that is model-independent.…”

“…[23]), theoretical research of new Higgs boson decay channels [30], deploying heavier eta meson states in AdS/QCD [31], confinement/deconfinement transition in QCD [32], quarkonium in a finite density plasma [33], time evolution in physical systems [34,35], etc. In projectile fragmentation reactions, fragment distributions show a sensitive dependence on the change in neutron density [36][37][38], which makes it possible to determine the neutron skin thickness of neutron-rich nuclei. In this study, the CIE method was adopted to quantify the CIE of nuclear density and fragment distributions in projectile fragmentation reactions.…”