Towards baryogenesis via absorption from Primordial Black Holes

TL;DR

This paper critically examines a proposed baryogenesis mechanism involving primordial black holes and particle absorption, identifying fundamental issues and demonstrating that it cannot fully account for observed baryon asymmetry.

Contribution

The paper provides an independent analysis of a baryogenesis model via PBH absorption, highlighting phenomenological and theoretical challenges and assessing its viability.

Findings

Absorption by PBHs initially increases baryon asymmetry but later erodes it.

PBH evaporation can halt absorption, allowing finite asymmetry.

Minimal models of CP-violation are insufficient to produce observed baryon asymmetry.

Abstract

Recently Dolgov and Pozdnyakov proposed a new baryogenesis mechanism in which baryon asymmetry is produced without violating baryon number at the Lagrangian level. In this scenario, baryon asymmetry is generated by absorption of a new particle X carrying baryon number onto Primordial Black Holes (PBHs). Assuming CP-violation, the particle X is absorbed at a different rate than the antiparticle $\bar{X}$, producing an asymmetry in the baryonic number. We independently test this scenario, finding that it suffers from two fundamental issues.\\ At the phenomenological level, strong absorption by PBHs initially increases the baryon asymmetry. However, at later times such asymmetry is completely absorbed by PBHs. In order to overcome this issue, we account for PBH evaporation, which provides a natural way of halting the absorption while keeping a finite baryon asymmetry. We provide a systematic study of the parameter space, identifying the regions leading to the production of the baryon asymmetry without violating the known constraints on PBHs concentration. At the theoretical level, a model realizing the CP-violation postulated in this scenario is difficult to realize. We show, by implementing a minimal model, that the framework proposed in the original work in order to produce CP-violation, even if qualitatively correct, is quantitatively in disagreement with the observed baryon asymmetry, namely this mechanism produces only a fraction of the total baryon asymmetry.