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.