Speaker: Shannon Cowell (University of Illinois)

Quenching of Weak Interactions in Nucleon Matter

In the past decade it has become clear that neutrinos play a dominant role in many astrophysical processes.  In the context of supernovae and neutron stars, for example, it is essential to know neutrino interactions with nuclear matter. However, current computer technology limits exact many-body calculations to nuclei with A <= 10. In nuclear matter, as well as for most nuclei like 12C, we must use approximate methods. The interaction between nucleons is too strong to be treated with simple perturbative techniques and a variety of approximations using effective interactions, such as Shell model RPA, have been developed. However, many of the modern calculations of neutrino interactions have used effective interactions with bare weak operators. It is well-known that this is inconsistent, and calculations must ultimately use both effective interactions and effective weak operators. The work presented represents the initial steps toward the development of a consistent and complete set of effective interactions and effective weak operators starting from realistic interactions. Preliminary studies of the structure of one-body effective weak operators and two-body effective interactions using Correlated Basis Theory will be presented. These have been used in calculations of neutrino mean free paths in cold symmetric nuclear matter and neutrino luminosities of nucleon matter at temperatures relevant in core-collapse supernovae. Though this work is on-going, these initial studies indicate that the neutrino mean free path is significantly enhanced relative to a non-interacting Fermi gas.