Impacts of Black-Hole-Forming Supernova Explosions on the Diffuse Neutrino Background

TL;DR

This paper models how black-hole-forming supernovae influence the diffuse supernova neutrino background, showing that their inclusion could double the expected neutrino detection rate and reduce the observation time needed.

Contribution

It introduces a comprehensive model accounting for black-hole-forming supernovae and their impact on the DSNB, highlighting their significance in neutrino detection predictions.

Findings

Including BH-forming SNe doubles the expected neutrino event rate.

The contribution of BH-forming SNe reduces the detection time at Hyper-Kamiokande.

Uncertainties remain in fallback duration and BH-forming SN fraction.

Abstract

Flux spectrum, event rate, and experimental sensitivity are investigated for the diffuse supernova neutrino background (DSNB), which originates from past stellar collapses and is also known as a supernova relic neutrino background. For this purpose, the contribution of collapses that lead to successful supernova (SN) explosion and black hole (BH) formation simultaneously, which are suggested to be a non-negligible population from the perspective of Galactic chemical evolution, is taken into account. If the BH-forming SNe involve the matter fallback onto the protoneutron star for the long term, their total emitted neutrino energy becomes much larger than that of ordinary SNe and failed SNe (BH formation without explosion). Then, in the case of the normal mass hierarchy in neutrino oscillations and with half of all core-collapse SNe being BH-forming SNe, the expected event rate according to the current DSNB model is enhanced by up to a factor of two due to the BH-forming SNe. While substantial uncertainties exist regarding the duration of the matter fallback, which determines the total amount of emitted neutrinos, and the fraction of BH-forming SNe, the operation time required to detect the DSNB at Hyper-Kamiokande would be reduced by such contribution in any case.