Reaction Dynamics and Multifragmentation in Fermi Energy Heavy Ion Reactions-猫眼课题宝

DOI：

10.1103/physrevc.69.044610

发表时间：

2003-08

期刊：

Physical Review C

影响因子：

3.1

通讯作者：

中科院分区：

物理与天体物理2区

文献类型：

作者：

R. Wada;T. Keutgen;K. Hagel;Yu-Gang Ma;J. Wang;M. Murray;L. Qin;P. Smith;J. Natowitz;R. Alfarro;J. Cibor;M. Cinausero;Y. Masri;D. Fabris;E. Fioretto;A. Keksis;S. Kowalski;M. Lunardon;A. Makeev;Nathalie Marie;E. Martin;Z. Majka;A. Martínez-Dávalos;A. Menchaca-Rocha;G. Nebbia;G. Prete;V. Rizzi;A. Ruangma;D. Shetty;G. Souliotis;P. Staszel;M. Veselský;G. Viesti;E. Winchester;S. Yennello;W. Zipper;Akira Ono

用尼姆罗德探测器阵列对26 A、35 A和47 A MeV的64 Zn +58 Ni、64 Zn +92 Mo、64 Zn +197 Au反应体系进行了实验研究，并采用反对称化的分子动力学模型计算了对应于软态方程和硬态方程的有效相互作用.直接的实验观测，如多重数分布，电荷分布，能量谱和速度谱，已被详细比较与那些的计算，并得到一个合理的协议。在Z >= 3的情况下，$\alpha$粒子和碎片的速度分布在软状态方程和硬状态方程的计算中表现出明显的差异。$\alpha$粒子和中等质量碎片（IMF的）的速度分布最好的刚性状态方程描述。上述直接观测量和椭圆流的强度对介质中核子-核子（NN）截面的变化都不敏感。用刚性状态方程计算的中心碰撞事件的详细分析表明，冷碎片发射的多重碎裂是这里研究的所有反应预测的一个共同特征。一个可能的multifragmentation的情况下，在复合系统的预平衡排放停止后，冷的光碎片形成在一个更热的气体核子和保持冷，直到复合系统underdoes multifragmentation。在47 A MeV下与197 Au反应时，发生了显著的径向膨胀。在47 A MeV下与~（58）Ni和~（92）Mo的反应中，半透明现象变得突出。不同的反应动力学极大地改变了发射碎片的运动学特征。这一方案给出了一致的解释，许多现有的实验结果在费米能域。

The reaction systems, 64Zn + 58Ni, 64Zn + 92Mo, 64Zn + 197Au, at 26A, 35A and 47A MeV, have been studied both in experiments with a 4$\pi$ detector array, NIMROD, and with Antisymmetrized Molecular Dynamics model calculations employing effective interactions corresponding to soft and stiff equations of state (EOS). Direct experimental observables, such as multiplicity distributions, charge distributions, energy spectra and velocity spectra, have been compared in detail with those of the calculations and a reasonable agreement is obtained. The velocity distributions of $\alpha$ particles and fragments with Z >= 3 show distinct differences in calculations with the soft EOS and the stiff EOS. The velocity distributions of $\alpha$ particle and Intermediate Mass Fragments (IMF's) are best described by the stiff EOS. Neither of the above direct observables nor the strength of the elliptic flow are sensitive to changes in the in-medium nucleon-nucleon (NN) cross sections. A detailed analysis of the central collision events calculated with the stiff EOS revealed that multifragmentation with cold fragment emission is a common feature predicted for all reactions studied here. A possible multifragmentation scenario is presented; after the preequilibrium emission ceases in the composite system, cold light fragments are formed in a hotter gas of nucleons and stay cold until the composite system underdoes multifragmentation. For reaction with 197Au at 47A MeV a significant radial expansion takes place. For reactions with 58Ni and 92Mo at 47A MeV semi-transparency becomes prominent. The differing reaction dynamics drastically change the kinematic characteristics of emitted fragments. This scenario gives consistent explanations for many existing experimental results in the Fermi energy domain.

Reaction Dynamics and Multifragmentation in Fermi Energy Heavy Ion Reactions

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