Detectable leptogenesis and explaining dark matter non-detection using non-standard cosmology and multi-component dark matter models

2026-07-22

The initial hint of DM came from F. Zwicky in 1933 while studying the Coma cluster. Since then, extensive evidence has confirmed DM's existence and its relic density has been precisely measured. However, the particle nature of DM remains unknown. Despite numerous experiments -direct, indirect, and collider searches, no signal has been detected. Recent limits from LUX-ZEPLIN 2024 have tightly constrained the DM parameter space, nearing the neutrino floor. This proposal addresses DM non-detection by opening up new parameter spaces that have not been fully explored. We will investigate three scenarios beyond the standard WIMP and FIMP models which have either faced significant constraints or are challenging to detect. First, we will explore baryon asymmetry through new diagrams contributing to lepton asymmetry and FIMP DM production from WIMPs in a non-standard cosmology. Additionally, lepton flavour violation, neutrino mass, and gauge coupling unification will be investigated. We will consider a super-WIMP-like mechanism for FIMP-type DM, with potential long-lived particle signals detectable at FASER/MATHUSLA and contributions to relativistic degrees of freedom observable at CMB-S4. Second, we will analyse inflationary models resulting in a low reheat temperature. By setting the mother particle mass higher than the reheat temperature, we can achieve FIMP DM production at stronger couplings due to the Boltzmann-suppressed number density, potentially explaining the lack of DM detection so far. Third, we will explore a multi-component DM model where one component annihilates into another which then annihilates into Standard Model particles. By adjusting the second component’s fraction, we can evade current bounds and offer future detection prospects. The first, inert component helps account for the total DM density. The proposal is timely in the context of DM non-detection and suggesting new detection avenues across various methods.

Italy

2026-01-01