U.S.-Brazil Collaborative Research: Non-Equilibrium and Isospin Effects in Nuclear Fragmentation

在这个由美洲项目资助的美巴合作项目中，密歇根州立大学的威廉·林奇和ManYee B. Tsang以及威斯康辛大学的威廉·a·弗里德曼将与巴西里约热内卢联邦大学理论小组的劳尔·多纳杰洛和塞尔吉奥·索萨合作。这些研究人员将进行协调研究，以解释实验多碎片数据。本研究的主要重点是对影响液气相变和核状态方程的同位旋依赖性研究的非平衡现象的识别和建模。该研究包括将数据与最先进的平衡统计多碎片模型和PI开发的膨胀蒸发源模型进行详细比较。它还涉及将在项目期间由该合作开发的新的非均衡模型的比较。这些结果将有助于确定大多数平衡模型所假设的平衡冻结结构的准确程度，并开发出可以用来分析具有重要非平衡贡献的数据的形式。这项对非平衡现象的合作研究是一项重点突出的理论努力，它扩展了密歇根州立大学国家超导回旋加速器实验室（NSCL）以及其他实验室所做的实验工作。该项目需要美国和巴西主要研究人员的专业知识，不仅是解释国家科学实验室反应项目数据的关键，也是解释其他飞行中稀有同位素设施研究数据的关键。

In this U.S.-Brazil collaborative project funded by the Americas Program, William G. Lynch and ManYee B. Tsang of Michigan State University and William A. Friedman of the University of Wisconsin will work with Raul Donangelo and Sergio Souza of the theory group at the Federal University of Rio de Janeiro. These researchers will make a coordinated study to interpret experimental multifragmentation data. The major focus of this investigation is on the identification and modeling of non-equilibrium phenomena that influence investigations of the isospin dependence of the liquid-gas phase transition and of the nuclear equation of state. The research involves detailed comparisons of data to state-of-the-art equilibrium Statistical Multifragmentation Models and to the Expanding Evaporating Source models that have been developed by the PI's. It also involves comparisons to new non-equilibrium models that will be developed by this collaboration during the project. The results will help to determine the degree to which the equilibrated freezeout configuration assumed by most equilibrium models is accurate and to develop formalisms with which one can analyze data with significant non-equilibrium contributions.This collaborative investigation of non-equilibrium phenomena is a well-focused theoretical effort that extends the experimental work done at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University as well as at other laboratories. The project requires the expertise of both the U.S. and Brazilian principal investigators and is key to interpreting data from not only reaction programs at NSCL but also research at other in-flight rare isotope facilities.