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

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 kpc in the Milky Way, itsν e spectrum can be precisely determined from the inverse beta-decay processν e þ p → e þ þ n, for which a 20 kiloton liquid-scintillator detector with the resolution similar to the Jiangmen Underground Neutrino Observatory may register more than 5000 events. We have to rely predominantly on the elastic neutrino-electron scattering ν þ e − → ν þ e − and the elastic neutrino-proton scattering ν þ p → ν þ p for the spectra of ν e and ν x , where ν denotes collectively neutrinos and antineutrinos of all three flavors and ν x for ν μ and ν τ 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.

Model-independent approach to the reconstruction of multiflavor supernova neutrino energy spectra

“…In this paper, we have improved the previous study in Ref. [34] in several important aspects. First, while the SN ν e energy spectrum can be precisely determined via the IBD data, the energy spectrum of ν e cannot be accurately extracted from the eES data.…”

“…The neutrino event rates in these channels for a JUNO-like detector have been calculated in Ref. [34] and will be recapped below for completeness.…”

“…In Ref [34], the SN neutrino events of IBD, pES and eES channels have been simulated for The IBD channel is the golden channel for SN neutrino detection in LS detectors due to the time coincidence of the prompt and slow signals and the large cross section of the IBD reaction [38,39]. This channel is solely sensitive to ν e .…”

“…In the previous work [34], we have already shown that it is possible to accomplish a complete reconstruction of the energy spectra of SN neutrinos ν e , ν e and ν x in a single large LS detector. One salient feature of the LS detector is its low energy threshold, which renders it capable of observing the recoiled protons resulting from the pES process that is mainly sensitive to SN ν x .…”

“…In Ref. [34], it has been assumed that ν e dominates over all other flavors in the eES channel and the detector response matrix between the initial neutrino energy and the observed event energy is approximately taken to be universal for all neutrinos. In the present work, this assumption is relaxed and the full detector response matrix will be implemented.…”