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

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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.