Low-Energy Neutrino Emission from Primordial Black Holes: A New Possibility of Observing Hawking Radiation

The study of primordial black holes (PBHs) and the Hawking radiation that they can generate is an important step in understanding the role of these phenomena in the cosmological evolution of the Universe. PBHs can be part of the dark matter, the seeds of supermassive black holes, and the sources of Hawking radiation, which, in contrast to the radiation from other black holes, can be observable. At the same time, under conditions of the evolution of the Universe from the Big Bang to the present day, PBHs lose most of their mass in the form of neutrino emission. This is because for black holes with $$M<10^{23}$$ g, apart from the emission of massless particles, the emission of the lightest massive particle, the neutrino, is added. Moreover, this emission turns out to be dominant, and since only black holes with masses $${\lesssim}10^{15}$$ g have evaporated significantly by the present time ( $$t_{0}=13.8$$ Gyr), the neutrino component dominates in the overall emission spectrum of PBHs. In this paper we present new estimates of the spectra of neutrinos emitted by PBHs of various masses, focusing attention on the low-energy ( $$\mathbf{E}_{\textrm{kin}}\in[0.01{-}1]$$ eV) emission for the first time. As a result of our calculations, we have shown that black holes in the range of masses $$[10^{9}{-}10^{11}]$$ g emit neutrinos with an intensity exceeding the background fluxes from known astrophysical sources in the low-energy range, while in the high-energy range the emission will be under the background without coming into conflict with observational constraints. These results open up new opportunities for the potential observation of emission from PBHs and can stimulate the development of neutrino detection technologies in the low-energy range. The observation of neutrinos in this range is one of the few possibilities to confirm the existence of Hawking radiation.