Neutrinos from Diffuse Supernova Background

TL;DR

The DSNB paper analyzes the cumulative flux of neutrinos from all core-collapse supernovae across cosmic history, linking it to the average CCSN neutrino emission, the cosmic CCSN rate, and flavor evolution. It presents a pinched thermal spectral model for CCSN neutrinos, relations for the cosmic CCSN rate from star formation and IMF, and the integral framework that yields the DSNB flux with attention to BH-formation effects and redshift. Detection prospects are surveyed across detectors and channels: $ar{\nu}_e$ via inverse beta decay in water Cherenkov and scintillator detectors (enhanced by gadolinium); $\nu_e$ via DUNE’s $\nu_e+^{40}$Ar interactions; and non-electron flavors via CE$\nu$NS in large direct-detection experiments. The paper emphasizes that measuring DSNB in all flavors is crucial to disentangle astrophysical and neutrino-physics uncertainties, with current hints of the DSNB in SK-Gd motivating near-term multi-channel strategies. The work highlights the DSNB’s potential to constrain the CCSN rate, black-hole-forming fraction, and average neutrino flux per event, marking a significant step toward a comprehensive, multi-messenger view of stellar death and neutrino physics.

Abstract

Neutrinos are the second most abundant particles in the universe according to the Standard Model, yet they are the least likely to interact. This feature implies that detecting a neutrino can reveal valuable insights into its source. Among the known sources of neutrinos, core-collapse supernovae are one of the most efficient factories. On average, a single collapse occurs every second in the observable universe, emitting approximately $10^{58}$ neutrinos. The total flux of neutrinos reaching Earth from all core-collapse supernovae across the universe is the diffuse supernova neutrino background (DSNB). Detection of the DSNB is just around the corner. This guaranteed flux of astrophysical neutrinos encodes information about the whole supernova population, including an answer to a currently unsolved question about the rate at which black holes form from massive stars. This chapter discusses the ingredients entering the DSNB calculation as well as current experimental limits and hints.

Figures (4)

• Figure 1: The DSNB for sum of all flavors assuming the Fermi-Dirac spectrum described by the temperature $T_\nu$ and the total energy emitted in all flavors $3\times 10^{53}$ erg. Different $T_{\nu}$ reflect how one source of uncertainty - the spectrum emitted from CCSN - can modify the DSNB. The shaded bands labeled by the Reactor, Solar, and Atmospheric mark the regions where these three nonreducible backgrounds affect the DSNB measurement.
• Figure 2: Upper limits on the $\bar{\nu}_e$ component of the DSNB from SK-IV Super-Kamiokande:2021jaq, SK-VI (first gadolinium loaded results) Super-Kamiokande:2023xup, and KamLand KamLAND:2021gvi (colored markers) together with theoretical predictions (gray lines). Figure extracted from Ref. Super-Kamiokande:2023xup.
• Figure 3: Schematic of tagging the inverse beta decay in water with dissolved gadolinium sulfate (Figure based on the one from Ref. Beacom:2003nk).
• Figure 4: The calculated sensitivity to the non-electron neutrino component of the DSNB in xenon-based CE$\nu$NS detectors. The y-axis ($\mathcal{E}_{\nu_x}$) is the total energy emitted by one non-electron neutrino flavor, whereas the x-axis ($\langle E_{\nu_x}\rangle$) shows the average neutrino energy. In addition, the current SK limit on $\bar{\nu}_e$Super-Kamiokande:2021jaq and the SNO limit on $\nu_e$SNO:2020gqd, the SN 1987A limit on $\nu_x$Suliga:2021hek, and the average emission per collapse in nominal theoretical DSNB models Moller:2018kpn are shown.