Uniform description of breakup mechanisms in central collision, projectile fragmentation, and proton-induced spallation
Uniform description of breakup mechanisms in central collision, projectile fragmentation, and proton-induced spallation
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DOI：
10.1103/physrevc.100.014602
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发表时间：
2019-07
影响因子：
3.1
通讯作者：
Jun Su;Long Zhu;Chen-Chen Guo-Chen;Zhen Zhang
中科院分区：
文献类型：
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作者：
Jun Su;Long Zhu;Chen-Chen Guo-Chen;Zhen Zhang
背景：在多种类型的核反应中观察到了多种碎裂模式，这可能对应于不同的碎裂机制。目的：本工作试图比较费米能附近中心重离子碰撞中碎片发射、抛射碎裂和质子诱导散裂的机制。方法：利用同位旋依赖量子分子动力学（IQMD）模型研究激发能小于2 MeV/核子的预碎片的碰撞，而蒸发来自预碎片的轻粒子由统计码双子描述。在IQMD模型中，应用具有泡利阻塞的二元核子-核子碰撞来从现象学上处理费米子运动的一些特征。然而，在核子之间的相对动量较小的区域，二元碰撞很少发生。因此，在IQMD模型中应用相空间密度约束（PSDC）的方法，以现象学的方式处理费米子运动的特征。结果：将各种可观测量的计算结果与现有数据进行比较。对比不仅显示了计算与数据的相似规律，而且强调了PSDC方法的作用。动力学轨迹表明，费米能附近中心HIC的压缩-膨胀相导致了旋节线分解。在射弹破碎和质子引起的散裂中，射弹在没有压缩的情况下被加热，然后在轻微膨胀的情况下冷却。然而，在动力涨落的驱动下，部分事件可能出现旋节线不稳定。这项研究最重要的结果也许是费米子特征在碎片发射机制中的重要作用。结论：该框架提供了中心碰撞、射弹碎片和质子诱导散裂中破碎机制的统一描述。
Background:A diversity of fragmentation modes has been observed in several types of nuclear reactions, which may correspond to different breakup mechanisms.Purpose:The present work is an attempt to compare the mechanisms of the fragment emission in central heavy-ion collision near the Fermi energy, projectile fragmentation, and proton-induced spallation.Method:The collisions until the prefragments with excitation energy less than 2 MeV/nucleon are studied using the isospin-dependent quantum molecular dynamics (IQMD) model, while the evaporations of light particles from the prefragments are described by the statistical codegemini. In the IQMD model, the binary nucleon-nucleon collisions with the Pauli blocking are applied to treat some features of fermionic motion phenomenologically. However, the binary collisions are scarce in the region where the relative momenta between the nucleons are small. Thus, the method of the phase space density constraint (PSDC) are applied in the IQMD model in order to treat phenomenologically the features of fermionic motion.Results:The calculations of various observables are compared to the available data. The comparison not only shows the similar regularities of the calculations to the data, but also emphasizes the role of the PSDC method. The dynamicaltrajectories show that the compression-expansion phase in the central HIC near the Fermi energy results in the spinodal decomposition. While in the projectile fragmentation and proton-induced spallation, the projectiles are heated without compression and then cool down with slight expansion. However, driven by the dynamical fluctuations, the spinodal instability is possible for a part of the events. The perhaps most important result of this study is the significant role of the fermionic feature in the mechanisms of the fragment emission.Conclusions:Theframework provides a uniform description of breakup mechanisms in central collision, projectile fragmentation, and proton-induced spallation.