Speaker
Description
Accurate estimates of (anti)neutrino spectra and luminosities are
essential for assessing the feasibility of detecting neutrinos from pre-supernova
stars. Using a recently proposed thermal quasiparticle random-phase
approximation (TQRPA) method, we investigated the effects of nuclear
temperature on pre-supernova (anti)neutrino emission. By comparing the $\nu_e$
and $\bar\nu_e$ spectra arising from neutral- and charged-current weak reactions
in cold versus thermally excited (hot) nuclei, we conclude that energy transfer from
hot nuclei not only enhances (anti)neutrino emission but also hardens the
spectrum. Using the MESA stellar evolution code, we generated density,
temperature, and chemical composition profiles for a pre-supernova model with
$M=14.\,M_\odot$. Based on these profiles, we computed the time evolution of
$\nu_e$, $\bar\nu_e$ luminosities and spectra resulting from both thermal and
nuclear processes. We find that, even one day before core collapse, the luminosity
of electron neutrinos produced via electron capture on hot nuclei exceeds by an
order of magnitude that from electron-positron pair annihilation. Furthermore, in the
context of electron antineutrino production, neutrino-antineutrino pair emission via
nuclear de-excitation (ND) is at least as significant as the electron-positron
annihilation process. We also demonstrate that flavor oscillations enhance the
high-energy contribution of the ND process to the electron antineutrino flux -- a
feature that may prove crucial for the detection of pre-supernova antineutrinos by
terrestrial detectors.
