Events at Physics
Events on Tuesday, September 28th, 2021
- Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
- Impact of EoS on Neutrino Opacities in Core-collapse Supernovae
- Time: 2:00 pm
- Speaker: Zidu Lin , University of Tennessee Knoxville/ORNL
- Abstract: Neutrinos radiate 99% of the energy and play a crucial role in the explosion mechanism and nucleosynthesis of core-collapse supernovae. The neutrino interactions in hot and dense matter is a complex problem due to bound nuclei and the strong nuclear forces. In this work we calculate the dynamic and static response of the neutral current and charged current neutrino-nucleon interactions, from low-density region near the neutrino sphere to high-density region up to approximately 1.5 saturation densities at finite T, by applying random phase approximation (RPA). We emphasize on the consistency between an equation of state (EoS) and the neutrino opacity, by using the density-dependent residual interactions, effective mass, single nucleon potentials directly derived from an EoS which matches experiment, theory, and observation in various density regimes. We further analyze the effect of EoSs on neutrino opacities by calculating the statistical uncertainties of neutrino opacities. We found that our neutral current static response based on RPA is close to the results from model-independent virial approximation at low density, and our description of neutrino opacities at high densities have large uncertainties due to still unclear strong (especially spin-dependent) nuclear forces.
- Host: Baha Balantekin
- Theory Seminar (High Energy/Cosmology)
- SU(4) Flavorful Portal Matter
- Time: 4:00 pm
- Place: Chamberlin 5280
- Speaker: George Wojcik, University of Wisconsin-Madison
- Abstract: Dark Matter (DM) and its potential interactions with the Standard Model (SM) continue to present a rich framework for model building. In the case of thermal DM of a mass between a few MeV and a few GeV, a compelling and much-explored framework is that of a dark photon/vector portal, which posits a new U(1) ``dark photon" which only couples to the SM via small kinetic mixing (KM) with the SM hypercharge. This mixing can be mediated at the one-loop level by portal matter (PM) fields which are charged under both the dark U(1) and the SM gauge group. Models with appropriate portal matter content to produce finite and calculable kinetic mixing can arise from non-minimal dark sectors, in which the dark U(1) is a subgroup of a larger gauge symmetry under which SM particles might have non-trivial representations. In this talk, I will describe a model in which the dark U(1) is unified with another popular extension to the SM gauge group, a local SU(3) flavor symmetry. The full dark/flavor symmetry group is SU(4)×U(1), incorporating the local SU(3) flavor symmetry with PM appearing as a vector-like "fourth generation" to supplement the three generations of the SM. I then discuss the phenomenology of the new extended dark gauge group at experimentally accessible energies, including non-trivial consequences of the flavor symmetry being unified with the dark sector. Note: This is a hybrid event. A zoom link will be distributed via the seminar mailing list. To join, email the organizer.
- Host: Lars Aalsma