Search for high energy γ-ray bursts from evaporation of primordial black holes

Abstract

PRIMORDIAL black holes (PBH) have been predicted by Hawking1. Density fluctuations in an early Universe might have given rise to a power law spectrum of low mass black holes which would evaporate by a thermal radiation process. Holes of initial mass 1012 kg might now be entering the terminal stages of evaporation, culminating in an explosion. The total energy liberated in particle emission and the corresponding radiation time scales depend critically on the nuclear models adopted2. The composite particle (CP) model predicts the liberation of 1027 J during the final 10−7 s of the explosion. About 10% of the total energy goes into γ rays with the spectrum peaked at 250 MeV. The elementary particle (EP) model predicts the liberation of 1030 photons during the final 0.1 s of the explosion at energies around 5 × 1012 eV (refs 3,4). We report here the results of a search for γ rays associated with the evaporation of PBHs, and upper limits are presented based on the latter model.