WIMPy Leptogenesis in Non-Standard Cosmologies

TL;DR

This paper explores how dark matter annihilations during non-standard cosmological periods can generate the universe's baryon asymmetry, expanding viable parameter space and offering new experimental probes.

Contribution

It introduces a minimal model for WIMP dark matter leptogenesis during non-standard cosmologies, analyzing three distinct cosmic histories and their impact on baryon asymmetry.

Findings

Allowed parameter space is enlarged with non-standard epochs.

Possibility of lighter dark matter masses in some scenarios.

Non-standard cosmologies provide complementary experimental probes.

Abstract

We study the possibility of generating baryon asymmetry of the universe from dark matter (DM) annihilations during non-standard cosmological epochs. Considering the DM to be of weakly interacting massive particle (WIMP) type, the generation of baryon asymmetry via leptogenesis route is studied where WIMP DM annihilation produces a non-zero lepton asymmetry. Adopting a minimal particle physics model to realise this along with non-zero light neutrino masses, we consider three different types of non-standard cosmic history namely, (i) fast expanding universe, (ii) early matter domination and (iii) scalar-tensor theory of gravity. By solving the appropriate Boltzmann equations incorporating such non-standard history, we find that the allowed parameter space consistent with DM relic and observed baryon asymmetry gets enlarged with the possibility of lower DM mass in some scenarios. While such lighter DM can face further scrutiny at direct search experiments, the non-standard epochs offer complementary probes on their own.