Physics
Scientific paper
Jul 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003icrc....3.1697b&link_type=abstract
Proceedings of the 28th International Cosmic Ray Conference. July 31-August 7, 2003. Trukuba, Japan. Under the auspices of the I
Physics
1
Scientific paper
Gamma-rays are, with antiprotons, a very efficient way to derive upper limits on the density of evaporating black holes. They have been successfully used in the last decades to severely constrain the amount of Primordial Black Holes (PBHs) in our Universe. This article suggests a little refinement, based on the expected background, to improve this limit by a factor of three. The resulting value is : ΩP bH < 3.3 × 10-9 . Small black holes could have formed in the early Universe if the density contrast was high enough (typically δ > 0.3 - 0.7 , depending on models). Since it was discovered by Hawking [1] that they should evaporate with a black-b o dy like spectrum of temperature T = hc3 /(8π k GM ), the emitted cosmic rays have ¯ been considered as the natural way, if any, to detect them. Those with initial masses smaller than M∗ ≈ 5 × 1014 g should have finished their evaporation by now whereas those with masses greater than a few times M∗ do emit nothing but extremely low energy massless fields. The emission spectrum for particles of energy Q per unit of time t is, for each degree of freedom, given by : d2 N Γs e Q - (1) = (-1)2s dQdt h xp hκ/4π 2 c where κ is the surface gravity, s is the spin of the emitted species and Γs is the absorption probability proportional to M 2 Q2 in the high energy limit (contributions of angular velocity and electric potential have been neglected since the black hole discharges and finishes its rotation much faster than it evaporates). PBHs have been investigated for many different purposes, including tests for quantum gravity [2] that are esp ecially active nowadays. As was shown by MacGibb on and Webb er [3], when the black hole temperature is greater than the quantum chromo dynamics confinement scale ΛQC D , quark and gluon jets are emitted instead of composite hadrons. This should be
Barrau Aurelien
Boudoul Gaelle
Derome Laurent
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