Primordial black holes as a source of extremely high energy cosmic rays

The origin of observed extremely high energy cosmic rays remains an astroph ysical enigma. We show that a single evaporating primordial black hole shou ld produce 8.5 . 10(14) particles over a 10(20) eV threshold. This emission results from direct production of fundamental constituents and from hadron ization of quarks and gluons. The induced flux on the Earth is studied as a function of the local density of exploding black holes and compared with e xperimental data. The discovery potential of future detectors is finally re viewed. (C) 2000 Elsevier Science B.V. All rights reserved.