Mapping the evolution of supernova-neutrino-boosted dark matter within the Milky Way

TL;DR

This paper studies how supernova-neutrino-boosted dark matter signals evolve within the Milky Way over time, highlighting the importance of diffuse background signals for future detection efforts.

Contribution

It provides a detailed analysis of the temporal and spatial behavior of local and diffuse supernova-neutrino-boosted dark matter signatures in the Milky Way, emphasizing the dominance of diffuse signals.

Findings

Diffuse DBDM dominates over local MW BDM in the nonrelativistic limit.

Relativistic MW BDM can become highly localized and transient.

Diffuse background signals are crucial for dark matter searches until a galactic supernova occurs.

Abstract

Supernova-neutrino-boosted dark matter (SN$\nu$ BDM) has emerged as a promising portal for probing sub-GeV dark matter. In this work, we investigate the behavior of BDM signatures originating from core-collapse supernovae within the Milky Way (MW) over the past one hundred thousand years, examining both their temporal evolution and present-day spatial distributions. We show that while the MW BDM signature is approximately diffuse in the nonrelativistic regime, it exhibits significant temporal variation and spatial localization when the BDM is relativistic. Importantly, we compare these local MW signatures with the previously proposed diffuse SN$\nu$ BDM (DBDM), which arises from the accumulated flux of all past supernovae in the Universe [Y.-H. Lin and M.-R. Wu, Phys. Rev. Lett. 133, 111004 (2024)]. In the nonrelativistic limit, DBDM consistently dominates over the local diffuse MW BDM signature. Only when the MW BDM becomes ultrarelativistic and transitions into a transient, highly-localized signal can it potentially surpass the DBDM background. This work thus reinforces the importance of DBDM for SN$\nu$ BDM searches until the next galactic SN offers new opportunities.