Genesis of baryon and dark matter asymmetries through ultraviolet scattering freeze-in

TL;DR

This paper proposes a novel ultraviolet freeze-in mechanism involving heavy Majorana neutrinos that simultaneously generates baryon and dark matter asymmetries, matching observed abundances with specific neutrino and dark matter mass ranges.

Contribution

It introduces a new UV-dominated freeze-in process via neutrino portal interactions that can produce both baryon and dark matter asymmetries in the early universe.

Findings

Dark sector can be populated through 2-to-2 scatterings after reheating.

Dark matter annihilation can deplete symmetric components, leaving an asymmetric relic.

Parameter space allows for heavy neutrino masses >10^{10} GeV and dark matter masses 0.1-1000 GeV.

Abstract

We introduce a new mechanism for the simultaneous generation of baryon and dark matter asymmetries through ultraviolet-dominated freeze-in scatterings. The mechanism relies on heavy Majorana neutrinos that connect the visible Standard Model sector to a dark sector through the neutrino portal. Following reheating of the visible sector to a temperature well below the heavy neutrino masses, we show that 2-to-2 scattering processes can populate the dark sector and generate both baryon and dark matter asymmetries. In some parameter regions, the dominant source of baryon asymmetry can be charge transfer from the dark sector, a process we call dark wash-in. We also demonstrate that annihilation of the dark matter to massless states within the dark sector can deplete the symmetric population without destroying the net baryon charge to leave only an asymmetric dark matter abundance today. Depending on the specific model parameters, the observed baryon and dark matter abundances can be attained with heavy neutrino masses $M_N \gtrsim 10^{10}$ GeV, and dark matter masses in the range 0.1 GeV $\lesssim m_\chi \lesssim 10^3$ GeV if the dark matter relic abundance is mainly asymmetric and even lower masses if it is symmetric.