Abstract
We propose a new mechanism where a multi-component dark sector generates the observed dark matter abundance and baryon asymmetry and thus addresses the coincidence between the two. The thermal freeze-out of dark matter annihilating into meta-stable dark partners sets the dark matter relic abundance while providing the out-of-equilibrium condition for baryogenesis. The meta-stable state triggers baryon asymmetry production by its decay well after the freeze-out and potentially induces a period of early matter domination before its decay. The dark matter and baryon abundances are related through number conservation within the dark sector (cogenesis). The “coincidence” is a natural outcome with GeV- to TeV-scale symmetric dark matter and the dark sector’s interactions with the Standard Model quarks. We present a UV-complete model and explore its phenomenological predictions, including dark matter direct detection signals, LHC signatures of new massive particles with color charges and long-lived particles with displaced vertices, dark matter-induced nucleon conversions, (exotic) dark matter indirect detection signals, and effects on the cosmological matter power spectrum. As a side result, we provide a novel analytical treatment for dark sector freeze-out, which may prove useful in the study of related scenarios.
Highlights
We propose a new mechanism where a multi-component dark sector generates the observed dark matter abundance and baryon asymmetry and addresses the coincidence between the two
The mechanism of “Baryogenesis from metastable WIMPs” [22] was proposed as an alternative where the prediction is more robust against model details: the baryon asymmetry is generated by a long-lived WIMP that undergoes CP- and B-violating decays after its thermal freeze-out
We identify a new mechanism for the joint generation of the baryon and DM abundances
Summary
We consider a dark sector with states χ1 and χ2 that evolve independently from the thermal SM bath. This is commensurate with initial conditions where χ1,2 decouple from SM while still being relativistic. The dark sector is assumed to be self-thermalized before freeze-out, characterised by a common dark temperature T , which is set to be comparable to or lower than the photon temperature T , T ≤ T , so that the SM sector always dominates the radiation energy of the Universe. The subscript “0” is used for present values (except for σ0 below), while the superscript denotes dark sector quantities that are measured in units of T
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