Towards a complete reconstruction of supernova neutrino spectra in future large liquid-scintillator detectors

TL;DR

This paper presents a method using singular value decomposition to accurately reconstruct supernova neutrino spectra in future large liquid-scintillator detectors, improving understanding of neutrino emissions from supernovae.

Contribution

It introduces a realistic reconstruction approach for supernova neutrino spectra utilizing SVD with regularization, applicable to upcoming large detectors like JUNO.

Findings

Reconstruction of  spectra with high precision.

Demonstrated validity using simulated supernova neutrino data.

Achieved over 5000 detected events for a supernova at 10 kpc.

Abstract

In this paper, we show how to carry out a relatively more realistic and complete reconstruction of supernova neutrino spectra in the future large liquid-scintillator detectors, by implementing the method of singular value decomposition with a proper regularization. For a core-collapse supernova at a distance of $10~{\rm kpc}$ in the Milky Way, its $\overline{\nu}^{}_e$ spectrum can be precisely determined from the inverse beta-decay process $\overline{\nu}^{}_e + p \to e^+ + n$, for which a $20~{\rm kiloton}$ liquid-scintillator detector with the resolution similar to the Jiangmen Underground Neutrino Observatory (JUNO) may register more than 5000 events. We have to rely predominantly on the elastic neutrino-electron scattering $\nu + e^- \to \nu + e^-$ and the elastic neutrino-proton scattering $\nu + p \to \nu + p$ for the spectra of $\nu^{}_e$ and $\nu^{}_x$, where $\nu$ denotes collectively neutrinos and antineutrinos of all three flavors and $\nu^{}_x$ for $\nu^{}_\mu$ and $\nu^{}_\tau$ as well as their antiparticles. To demonstrate the validity of our approach, we also attempt to reconstruct the neutrino spectra by using the time-integrated neutrino data from the latest numerical simulations of delayed neutrino-driven supernova explosions.