Orateur
Description
In heavy-ion collisions at several hundred MeV/nucleon, a compressed nuclear system is formed to about twice the saturation density and then rapidly expands. It has been a theoretical challenge to extract information about nuclear matter properties such as the EOS of isospin-asymmetric nuclear matter. Since light clusters and heavier fragment nuclei are abundantly produced, they can influence the global collision evolution.
The antisymmetrized molecular dynamics (AMD) model, with an extension for cluster formation in the final state of each NN collision, can reasonably reproduce the overall multiplicities of light clusters such as d, t, 3He and 4He. However, the comparison of the three-dimensional momentum distributions of clusters with the SpiRIT data for collisions at 270 MeV/nucleon has shown that the cluster production is systematically underestimated by AMD around the center of the expanding system. Varying the inmedium NN matrix element does not solve this problem. This suggests some insufficiency of momentum fluctuation.
In this talk, I will present recent advances in the interpretation and treatment of the momentum width inherent in Gaussian wave packets in AMD. In the improved method, the momentum width is activated to appropriately influence the time evolution, by introducing wave packet splitting for nucleons and clusters as the isolation of the wave packet increases due to mean-field propagation. The momentum width is also activated at NN collisions. In nucleon knockout reactions, we have confirmed that this method significantly improves the momentum distribution of the residual nucleus.
In central heavy-ion collisions, the momentum fluctuation significantly increases cluster formation around the center of the system. The remaining deviation of the triton yield in the neutron-rich 132Sn + 124Sn system may indicate an unexpectedly large N/Z ratio in the central region or some other anomaly in triton production.
