Our knowledge of properties of neutron-rich nuclear matter, especially the density dependence of nuclear symmetry energy, is important for understanding many critical issues in nuclear physics, astrophysics and cosmology. The density and momentum dependence of the nucleon isovector potential is the most fundamental but currently very poorly known quantity determining properties of neutron-rich nuclear matter. Heavy-ion reactions, especially those induced by high energy radioactive beams, provide us the unique means to investigate properties of neutron-rich nuclear matter in terrestrial laboratories. In concert with the experimental efforts undertaken at several radioactive beam facilities in the US and abroad, I shall develop new theoretical tools to explore signatures of the density and momentum dependence of the isovector nucleon potential and the corresponding symmetry energy; continue to provide theoretical assistances in planning and data analyses of experiments; and evaluate timely astrophysical impact of the symmetry energy constrained by the latest terrestrial nuclear laboratory data.
While carrying out the proposed work, I will carefully integrate my research and the education of students. Several undergraduate and graduate students will participate in carrying out the proposed work. I will emphasize and encourage early involvement of undergraduate students in research. This experience not only plays a vital role in their complete education but also provides a solid basis for them to become next generation scientists and engineers. Moreover, the continued NSF funding will also help significantly improve the environment and infrastructure for research, especially in nuclear physics and astrophysics, at Texas A&M University-Commerce.
Neutrons and protons are fundamental building blocks of matter. Understanding the nature of neutron-rich nucleonic matter is a major thrust of current reserach in both nuclear physics and astrophysics. It was identified as a major scientific challenge in nuclear physics in the 2007 Long Range Plan prepared by the US NSAC (Nuclear Science Advisory Committee). To help realize this ultimate goal having significant ramifications in several sub-fields of physical science and national security, the overall objective of this RUI (Research at Undergraduate Institutions) grant is to constrain the symmetry energy of dense neutron-rich nucleonic matter using nuclear reactions induced by high energy rare isotopes and examine its astrophysical impacts. The nuclear symmetry energy encodes the energy associated with the neutron-proton asymmetry in nuclear matter. It is a quantity very poorly known especially at high densities. However, it is critical for understanding not only the structures of rare isotopes but also novel phenomena in astrophysics. Using several new theoretical tools developed with the NSF support, we have succeeded in narrowing down the nuclear symmetry energy to a small range at low and intermediate densities by comparing our model calculations with experimental data from several laboratories. Impacts of this constrained symmetry energy on sevarl properties of neutron stars have been examined and compared with latest observations. Moreover, we have made predictions and suggested new ways to constrain the symmetry energy at very high densities reachable in the center of neutron stars using data to be available soon from experiments at advanced rare isotope beam facilities and observations using advanced x-ray satellites and gravitational wave detectors. While carrying out the proposed work, we have also succeeded in promoting a closer integration of research and education in both undergraduate and graduate education at Texas A&M University-Commerce. Totally eleven undergraduate and master-level graduate students participated in various parts of this project. Their participation in this project not only played a vital role in their complete education but also provided them a solid basis for their choice of where to take their career after graduation. Most of these students have gone to top Ph.D programs, been employed in industry or became K-12 teachers. Moreover, the NSF funding also helped significantly in improving the research environment and infrastructure at Texas A&M University-Commerce.
