Neutrinos in Astrophysics and Cosmology

Neutrinos in Astrophysics and Cosmology Neutrinos in astrophysics and cosmology The proposed research on astrophysical and cosmological neutrinos, from MeV to TeV, is interdisciplinary, being at the interface of nuclear physics, particle physics, and astrophysics. It has the potential to deepen existing knowledge, expand in new directions and build novel cross-discipline links. Specifically, it will study neutrino oscillations in core collapse supernovae over the ~ 10 s of cooling of the star. Time dependent features like the spectral splits will be examined as identifiers of the neutrino mass hierarchy. The possibility to do tomography of the star with oscillations, due to their sensitivity to the matter density profile, will be discussed. Interesting connections with nuclear physics are the sensitivity of the pre-bounce neutrino flux to the nuclear symmetry energy, and learning about the equation of state of nuclear matter by measuring the binding energy of the proto-neutron star. The results for an individual collapsing star will then be applied to the diffuse flux of supernova neutrinos, which is within the reach of near future experiments, and has the unique potential to image the entire supernova population in its diversity. It is of particular interest to study what physics can be learned, from a detection of the diffuse flux, once this diversity is included: e.g., whether one can distinguish the contribution of certain collapse types (like supernovae with oxygenneon- magnesium cores), or if it will be possible to distinguish the mass hierarchy. To develop updated predictions of the flux and event rates, using recent measurements of the supernova rate and including site-specific backgrounds, is important for guidance of experimental searches. Dr. Lunardini also plans to contribute to understanding the high energy neutrino sky, which is still largely mysterious, and is now finally probed by km3 detectors. These detectors could see neutrinos from slow jets, if the observed supernova-Gamma Ray Burst association is a manifestation of a general phenomenon of collapsing stars. The spectrum and oscillatory pattern of the flux will carry information on the jet parameters, and its depth in particular. If proton jets from supernova remnants are responsible for the Fermi Bubbles, seen in gamma rays, these striking features should be observed in neutrinos, depending on the detector location. Another theme of research will be the connection between neutrinos and cosmological relics, with focus on neutrinos as signatures of cosmic strings and of dark matter annihilation. Annihilation in stars at and after core collapse is still relatively unexplored, and could have an interesting phenomenology. The proposed research will be fertile of new collaborations, some of which will be cross-field, involving astrophysicists Razzaque and Messer, and particle physicist Tamborra. It has strong emphasis on future experiments, and will contribute to the scoping activity on DUSEL and other underground facilities. Broader impacts Being timely in a rapidly growing field, the project represents an opportunity for a postdoc, who will benefit from Dr. Lunardinis extended network of collaborators. Being accessible scientifically and university-based, it has potential for undergraduate and graduate mentoring, which is valuable considering that many neutrino researchers are based at national laboratories. Having already mentored two female researchers (postdoc and student), Dr. Lunardini hopes to continue to serve as a role model for underrepresented groups.