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arXiv 1502.00778nucl-thnucl-ex
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中能重离子碰撞中子/质子比之谜的再探讨

Revisit of the neutron/proton ratio puzzle in intermediate-energy heavy-ion collisions

Hai-Yun Kong, Yin Xia, Jun Xu, Lie-Wen Chen, Bao-An Li, Yu-Gang Ma

摘要:

在一个新改进的同位旋相关Boltzmann-Uehling-Uhlenbeck输运模型IBUU 11中引入一个新的同位旋和动量相关相互作用,研究了核对称能密度依赖性和中子-质子有效质量分裂$E_{sym}(ρ)$对自由核子和轻团簇中子/质子比的相对影响.发现$m^*_n-m^*_p$比$E_{sym}(ρ)$具有相对更强的效应,并且$m^*_n\leq m^*_p$的假设导致更高的中子/质子比。此外,这一发现是独立的介质中核子-核子截面使用。然而,我们的计算结果使用$E_{sym}(ρ)$和$m^*_n-m^*_p$都在其目前的不确定性范围内都是太低的最近NSCL/MSU双中子/质子比数据相比,从中央$^{124}$ Sn+ $^{124}$ Sn和$^{112}$ Sn+ $^{112}$ Sn碰撞在50和120 MeV/u,因此呼吁新的机制来解释在实验中观察到的令人困惑的高中子/质子比。

英文摘要:

Incorporating a newly improved isospin- and momentum-dependent interaction in the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model IBUU11, we have investigated relative effects of the density dependence of nuclear symmetry energy $E_{sym}(ρ)$ and the neutron-proton effective mass splitting $m^*_n-m^*_p$ on the neutron/proton ratio of free nucleons and those in light clusters. It is found that the $m^*_n-m^*_p$ has a relatively stronger effect than the $E_{sym}(ρ)$ and the assumption of $m^*_n\leq m^*_p$ leads to a higher neutron/proton ratio. Moreover, this finding is independent of the in-medium nucleon-nucleon cross sections used. However, results of our calculations using the $E_{sym}(ρ)$ and $m^*_n-m^*_p$ both within their current uncertainty ranges are all too low compared to the recent NSCL/MSU double neutron/proton ratio data from central $^{124}$Sn+$^{124}$Sn and $^{112}$Sn+$^{112}$Sn collisions at 50 and 120 MeV/u, thus calling for new mechanisms to explain the puzzlingly high neutron/proton ratio observed in the experiments.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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