Secondary decay effects of the isospin fractionation in the projectile fragmentation at GeV/nucleon
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Secondary decay effects of the isospin fractionation in the projectile fragmentation at GeV/nucleon Chen-Chen Guo1
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Jun Su1
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Long Zhu1
Received: 29 May 2020 / Revised: 28 October 2020 / Accepted: 3 November 2020 Ó China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society and Springer Nature Singapore Pte Ltd. 2020
Abstract The isospin fractionations in 124 Sn, 107 Sn ? 120 Sn at 600 MeV/nucleon, and 136 Xe, 124 Xe ? 208 Pb at 1000 MeV/nucleon are investigated by the isospin-dependent quantum molecular dynamics model coupled with the statistical code GEMINI. The yield ratio as a function of the binding energy difference for light mirror nuclei 3 H/ 3 He, 7 Li/7 Be, 11 B/11 C, and 15 N/15 O is applied to estimate the ratio between neutrons and protons in the gas of the fragmenting system. By comparing the estimated values resulting from the simulations with and without the GEMINI code, it was found that the secondary decay distorts the signal of the isospin fractionation. To minimize the secondary decay effects, the yield ratio of the light mirror nuclei 3 H/3 He as well as its double ratio between two systems with different isospin asymmetries of the projectiles is recommended as robust isospin observables. Keywords Quantum molecular dynamics model (QMD) Isospin fractionation Secondary decay effect
This work was supported by the Natural Science Foundation of China under (Nos. U2032137 and U1832182), the Natural Science Foundation of Guangdong Province, China (No.18zxxt65), and Fundamental Research Funds for the Central Universities (No. 19lgpy306). & Chen-Chen Guo [email protected] 1
Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China
1 Introduction Investigations on fractionation have stimulated significant theoretical and experimental efforts in many branches of science and technology [1, 2]. In recent years, there has been increasing interest in nuclear isospin fractionation, which indicates the separation of neutron-rich gas during a liquid-gas phase transition in nuclear matter [3–6]. It was reported in the early 1980s although the concept of isospin fractionation was not applied. For example, it was found that fragment emission amplified the ratio of free neutrons to protons relative to that in the total system [7]. In 2000, the concept of isospin fractionation was used to describe the measurement of the isotopic distributions of light particles and intermediate mass fragments in the collisions between tin isotopes at 50 MeV/nucleon [8]. Isospin fractionation is an important phenomenon in heavy ion collisions in the energy region from the Fermi energy to gigaelectron volt. It has been proposed that the observable associated with the isospin fractionation is sensitive to the isospin dependence of the nuclear equation-of-state in isospin-asymmetric nuclear matter [9–11]. The differential isospin fract
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