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arXiv 2402.19210nucl-th
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从Pb和Ca同位素的双核子分离能研究对称能

Symmetry Energy from Two-Nucleon Separation Energies of Pb and Ca Isotopes

Soongsil University(崇实大学);Hanyang University(汉阳大学);RIKEN, Nishina Center for Accelerator-Based Science(理化学研究所仁科加速器科学中心);University of Aizu(会津大学);Università degli Studi(米兰大学);INFN sezione di Milano(意大利国家核物理研究所米兰分部)

Myeong-Hwan Mun, Eunja Ha, H. Sagawa, Gianluca Colò, Myung-Ki Cheoun

AI总结:

通过分析Pb和Ca同位素的双质子和双中子分离能,结合不同核质量数据,研究对称能与库仑能的关系,并推导出对称能系数。

摘要:

我们利用不同的核质量数据研究对称能与双质子和双中子分离能的关系。为此,我们使用了连续变形相对论Hartree-Bogoliubov理论(DRHBc)、FRDM2012和AME2020数据。首先,我们通过减去库仑能的贡献,研究Pb和Ca同位素的双质子和双中子分离能,发现它们与中子数以及中子皮厚度有强相关性。通过计算两种分离能的相对差异,我们从Pb和Ca同位素中推导出对称能。由于核表面对对称能有贡献,我们通过几种质量模型减去表面贡献来得到体积对称能。获得的对称能系数,$a_{sym}$,对于Pb同位素为20.0 $\sim$ 22.7 MeV,对于Ca同位素为18.7 $\sim$ 19.3 MeV,来自DRHBc质量表数据;而其他质量表的结果为19.6 $\sim$ 22.1(20.7 $\sim$ 22.3)MeV对于Pb同位素,以及18.9 $\sim$ 19.0(19.6 $\sim$ 19.7)MeV对于Ca同位素,来自AME2020(FRDM2012)数据。对于每个质量模型,我们还提供了对称系数的体积贡献,$a_{sym}^v$,这取决于表面能量系数与体积能量系数的比值,$a_s / a_v$。由于这个比值既不由核理论决定,也不由实验数据确定,我们通过使用这个比值作为自由参数来研究$a_{sym}^v$,并获得了几乎不依赖于核模型和同位素链的$a_{sym}^v$ = 27.0 MeV,其中比值$a_s / a_v$被约束为1.10 $\sim$ 1.13。

英文摘要:

We investigate the symmetry energy in relation with the two-proton and two-neutron separation energies using different nuclear mass data. For this aim, we exploit the deformed relativistic Hartree-Bogoliubov theory in the continuum (DRHBc), FRDM2012 and AME2020 data. First, we study the two-proton and two-neutron separation energies in Pb and Ca isotopes by subtracting the contribution of Coulomb energy. They show a strong correlation with neutron number as well as with the neutron skin thickness. By taking the relative difference of both separation energies, we derive the symmetry energy from Ca and Pb isotopes. Since the nuclear surface contributes to the symmetry energy, we deduce the volume symmetry energy by subtracting the surface contribution using several mass models. The obtained symmetry energy coefficient, $a_{sym}$, is 20.0 $\sim $ 22.7 MeV for Pb isotopes and 18.7 $\sim$ 19.3 MeV for Ca isotopes from the DRHBc mass table data, while the results from other mass tables are 19.6 $\sim$ 22.1 (20.7 $\sim$ 22.3) MeV for Pb isotopes and 18.9 $\sim$ 19.0 (19.6 $\sim$ 19.7) MeV for Ca isotopes from AME2020 (FRDM2012) data. The volume contribution to the asymmetry coefficient, $a_{sym}^v$, which depends on the ratio of the surface to the volume energy coefficients, $a_s / a_v$, is also provided for each mass model. Since the ratio $a_s / a_v$ is neither determined by nuclear theory, nor by experimental data, we have investigated $a_{sym}^v$ by using the ratio $a_s / a_v$ as a free parameter, and have obtained $a_{sym}^v = $ 27.0 MeV, almost irrespective of nuclear model and isotopic chain, with the ratio $a_s / a_v$ constrained as $a_s / a_v = 1.10 \sim 1.13$.

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