Research in Nuclear Astrophysics, Nuclear Physics, and Particle Physics

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This NSF grant is intended to support three main programs, all aimed at understanding supernovae or x-ray bursts, two of the most dramatic events in the cosmos. The first two will study nuclei or nuclear reactions that are important to processes in stars that synthesize many of the nuclei of which our universe is comprised. Both processes involve unusually hot stellar environments, which result in the processes proceeding at very rapid rates. Thus they can add many protons, in one case, or neutrons, in the other, without undergoing the decays that usually maintain nuclei at or near stability. Understanding these processes necessitates knowing the properties of, and reactions on, the nuclei through which they pass, so both of these programs focus on short-lived nuclei. These nuclei can only be produced at radioactive nuclear beam facilities, necessitating our working at accelerator laboratories at Michigan State University, TRIUMF in Canada, or RIKEN in Japan. A good understanding of the nuclear aspects of the processes by which nuclei are synthesized ultimately allows inversion of the predicted nuclear abundances to understand or constrain the stellar environments in which these processes occur. Thus these two programs are aimed at understanding both the nucleosynthesis from these processes and the conditions in which the processes operate. Much of this research will produce data of interest to both nuclear astrophysics and nuclear physics.The third project is for development of an observatory of neutrinos emitted from a galactic supernova. While this will ultimately be a much larger effort than could be supported by the present grant, we plan over the next three years to perform the calculations and develop the detectors that will be essential for this observatory. The neutrinos from a supernova are expected to arrive at earth in several tens of seconds, during which time we should be able to obtain an extraordinary amount of diagnostic information about the process of stellar collapse and the ensuing events that accompany the explosion of a supernova and the collapse of its core to a neutron star or black hole. It may also be possible to use the data to determine the mass of the most massive neutrinos, information that would be extremely useful to other areas of astrophysics and to particle physics.