Nuclear, Particle, and Weak Interaction Physics of the Big Bang and Stellar Collapse

University Of California-San Diego, La Jolla CA

Investigators

Abstract

The research supported in this Project will provide insights into how atomic nuclei and radiation behave in extreme conditions of temperature and density. In turn, this research will seek to leverage these insights to provide important clues about the nature of elementary particles, the mysterious neutrinos in particular, and about how the elements are synthesized in nature, e.g., in the fiery interiors of stars. These are grand science questions and a significant part of the world's physics and astronomy endeavor is directed toward answering them. For example, recent experiments have revealed some of the properties of the ghost-like neutrinos, and planned experiments seek to uncover more. An objective of this Project will be to better understand the implications of these properties for the grand questions described above. This will require honing humanity's fundamental theory of nature, i.e., Quantum Mechanics, into a tool capable of modeling the behavior of neutrinos in the extreme environments provided by the cosmos. Another key product of this Project will be the training of young nuclear physicists, at both the graduate and undergraduate levels. The research supported in this Project will be directed toward probing the fundamental physics of neutrinos and nuclei by exploiting the intersection of exciting new developments in nuclear physics and neutrino physics on the one hand, with rapidly advancing probes of astrophysical environments on the other. A key issue in this enterprise will be studying how neutrinos interact in dense matter and how these interactions may cause neutrinos to change their flavors (e.g., electron type neutrinos changing to tau type and vice versa) and/or their spins (e.g., left-handed to right-handed, and vice versa - if neutrinos are Majorana in character this is tantamount to changing neutrinos to antineutrinos). This is a fiercely nonlinear problem because neutrino flavor/spin determines how neutrinos interact, and how they interact determines how flavors/spin change. To these ends, the P.I. and his graduate and undergraduate students will work toward: (1) Understanding and modeling the quantum kinetic equations which govern neutrino flavor and spin evolution in a general medium; (2) Constructing large-scale numerical simulations of neutrino flavor/spin evolution in various supernova, stellar collapse, and compact object merger environments and assessing the feedback of this neutrino flavor physics on the prospects for the synthesis of nuclei in these sites; (3) Understanding nuclear structure, neutrino-nucleus interactions, nuclear partition functions, and weak strength distributions in high temperature environments.