Getting the most from the detection of Galactic supernova neutrinos in future large liquid-scintillator detectors

Future large liquid-scintillator detectors can be implemented to observe neutrinos from a core-collapse supernova in our Galaxy in various reaction channels: (1) the inverse beta decay ${\overline{\nu }}_e+p\to n+e^{+}$, (2) the elastic neutrino-proton scattering $\nu +p\to \nu +p$, (3) the elastic neutrino-electron scattering $\nu +e^{-}\to \nu +e^{-}$, (4) the charged-current ${\nu }_e$ interaction ${\nu }_e+{}^{12}\mathrm{C}\to e^{-}+{}^{12}\mathrm{N}$, (5) the charged-current ${\overline{\nu }}_e$ interaction ${\overline{\nu }}_e+{}^{12}\mathrm{C}\to e^{+}+{}^{12}\mathrm{B}$, and (6) the neutral-current interaction $\nu +{}^{12}\mathrm{C}\to \nu +{}^{12}{\mathrm{C}}^{*}$. The less abundant ${}^{13}\mathrm{C}$ atoms in the liquid scintillator are also considered as a target, and both the charged-current interaction ${\nu }_e+{}^{13}\mathrm{C}\to e^{-}+{}^{13}\mathrm{N}$ and the neutral-current interaction $\nu +{}^{13}\mathrm{C}\to \nu +{{}^{13}\mathrm{C}}^{*}$ are taken into account. In this work, we show for the first time that a global analysis of all these channels at a single liquid-scintillator detector, such as Jiangmen Underground Neutrino Observatory, is very important to test the average-energy hierarchy of supernova neutrinos and how the total energy is partitioned among neutrino flavors. In addition, the dominant channels for reconstructing neutrino spectra and the impact of other channels are discussed in great detail.

Figure 1

The event spectra of prompt neutrino signals at JUNO for a galactic SN at a distance of 10 kpc, where $E_{\mathrm{d}}$ stands for the visible energy in the detector. The SN neutrino fluxes are the same as in Table 1.

Figure 2

Allowed regions of the luminosity ($E_{{\overline{\nu }}_e}^{\mathrm{tot}}$) and average energy ($⟨E_{{\overline{\nu }}_e}⟩$) of ${\overline{\nu }}_e$ at the 90% C.L. in the individual (left panel) and global (right panel) fitting of the IBD and ${}^{12}\mathrm{C}\text{−}\mathrm{CC}$ processes. The left panel uses an IBD efficiency of 95%, whereas a variation of the IBD efficiency has been applied in the right panel. Note that the crosses stand for the best-fit values, and the right panel is rescaled for better visibility.

Figure 3

Allowed regions of the luminosity ($E_{{\nu }_e}^{\mathrm{tot}}$) and average energy ($⟨E_{{\nu }_e}⟩$) of ${\nu }_e$ at the 90% C.L. in the individual (left panel) and global (right panel) fitting of the $e\mathrm{ES}+{}^{13}\mathrm{N}\text{−}\mathrm{CC}$ and ${}^{12}\mathrm{C}\text{−}\mathrm{CC}$ processes. The left panel uses an IBD efficiency of 95%, whereas variations of the IBD efficiency have been applied in the right panel. Note that the crosses stand for the best-fit values, and the right panel is rescaled for better visibility.

Figure 4

Allowed regions of the luminosity ($E_{{\nu }_x}^{\mathrm{tot}}$) and average energy ($⟨E_{{\nu }_x}⟩$) of ${\nu }_x$ at the 90% C.L. in the individual (left panel) and global (right panel) fitting of the $e\mathrm{ES}+{}^{13}\mathrm{N}\text{−}\mathrm{CC}$, $p\mathrm{ES}$, ${}^{12}\mathrm{C}\text{−}\mathrm{NC}$, and ${}^{13}\mathrm{C}\text{−}\mathrm{NC}$ processes. The left panel uses an IBD efficiency of 95%, whereas variations of the IBD efficiency have been applied in the right panel. Note that the crosses stand for the best-fit values, and the right panel is rescaled for better visibility.

Figure 5

Allowed regions of the neutrino energy ratios ($R_{{\nu }_e}$, $R_{{\overline{\nu }}_e}$, $R_{{\nu }_x}$) at the $1\sigma$, $2\sigma$, and $3\sigma$ C.L. are shown for the NO (upper panel) and IO (lower panel) cases, respectively. The crosses stand for the best-fit values.

Figure 6

The $\mathrm{\Delta }{\chi }^2$ distributions for the gravitational binding energy $E^{\mathrm{tot}}$ in the NO (upper panel) and IO (lower panel) cases in the global-fitting scenarios. The solid lines, short dashed lines, dotted lines, and dash-dotted lines stand for the cases of using all detection processes, without the $p\mathrm{ES}$ process, without the $e\mathrm{ES}+{}^{13}\mathrm{N}\text{−}\mathrm{CC}$ processes, and without both $p\mathrm{ES}$ and $e\mathrm{ES}+{}^{13}\mathrm{N}\text{−}\mathrm{CC}$ processes, respectively.