Probing Memory-Burdened Primordial Black Holes with High-Energy Neutrinos

Abstract

The memory-burden effect can suppress the late-time evaporation of primordial black holes (PBHs), allowing those that would otherwise have evaporated via Hawking radiation to survive until the present epoch. These lighter PBHs emit high-energy and ultra-high-energy neutrinos, opening the tentalizing possibility of discovery via neutrino telescopes. We study the constraints on memory-burdened PBHs from current IceCube HESE, MESE, and EHE data; and forecast the sensitivity reach of IceCube-Gen2 radio and GRAND200k. In particular, we study how this signal depends on whether the initial PBH population is described by a log-normal mass function or by a monochromatic one. We find that log-normally distributed populations can be more strongly constrained than monochromatic populations with the same median mass primarily because their low-mass tails enhance the high-energy neutrino flux. We show that current IceCube data provide the leading limits for a lower memory burden parameter $k$, whereas the projected radio detectors become substantially more sensitive for higher values of $k$. We also study a scenario where future experiments would see a positive signal coming from PBHs. We consider a representative 30-event signal in IceCube-Gen2 radio and GRAND200k and study how well one could distinguish the two mass-function hypotheses. We find that it is easier to disfavor the monochromatic distribution when the log-normal distribution is assumed to be true. Finally, we study how well the parameters of the memory-burdened PBHs can be estimated in these future experiments.