Browsing by Subject "neutrino oscillations"

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    Collective Neutrino Oscillations in Neutrino-Driven Winds
    (2020-12) Xiong, Zewei
    A proto-neutron star produced in a core-collapse supernova (CCSN) drives a wind by its intense neutrino emission. Those dense neutrino media can undergo various collective neutrino oscillations and exert feedback on the wind through neutrino absorptions and emissions. In this thesis, I study the effects of two collective oscillations: the active-sterile neutrino and fast flavor oscillations.I implement active-sterile neutrino oscillations in a steady-state model of this neutrino-driven wind to study their effects on the dynamics and nucleosynthesis of the wind in a self-consistent manner. For the higher mass values of a sterile neutrino on the eV scale, oscillations can reduce the mass loss rate and the wind velocity by factors of ~ 1.6–2.7 and change the electron fraction critical to nucleosynthesis by a large amount. In the most dramatic cases, oscillations shift nucleosynthesis from dominant production of 45Sc to that of 86Kr and 90Zr during the early epochs of the CCSN evolution. Active-sterile neutrino oscillations in the wind exhibit interesting features due to various feedbacks between the potentials from neutrino-electron and neutrino-neutrino forward scattering. These feedbacks were studied in detail. In addition, I study the effects of fast neutrino flavor oscillations on the νp process in neutrino driven winds. Using the unoscillated neutrino emission characteristics from two CCSN simulations representative of relevant progenitors at the lower and higher mass end, I study the potential effects of fast flavor oscillations on neutrino-driven winds and their nucleosynthesis. Such oscillations are found to increase the total mass loss by factors up to ~ 1.5–1.7 and lead to significantly more proton-rich conditions. The latter effect can greatly enhance the production of 64Zn and the so-called light p-nuclei 74Se, 78Kr, and 84Sr.