Baryogenesis from Primordial Blackholes after Electroweak Phase Transition

Incorporating a realistic model for accretion of ultra-relativistic particles by primordial blackholes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch ∼ 10−33 sec to ∼ 5 × 10−9 sec. In this paper we use Barrow et al’s ansatz to model blackhole evaporation in which the modified Hawking temperature goes to zero in the limit of the blackhole attaining a relic state with mass∼ mpl. Both single mass PBH case as well as the case in which blackhole masses are distributed in the range 8×102 3×105 gm have been considered in our analysis. Blackholes with mass larger than ∼ 105 gm appear to survive beyond the electroweak phase transition and, therefore, successfully manage to create baryon excess via X − X̄ emissions, averting the baryon number wash-out due to sphalerons. In this scenario, we find that the contribution to the baryon-to-entropy ratio by PBHs of initial mass m is given by ∼ ǫζ(m/1 gm)−1, where ǫ and ζ are the CP-violating parameter and the initial mass fraction of the PBHs, respectively. For ǫ larger than ∼ 10−4, the observed matter-antimatter asymmetry in the universe can be attributed to the evaporation of PBHs. E-mail: [email protected] E-mail: [email protected] E-mail: [email protected]