KeV Warm Dark Matter and Composite Neutrinos

TL;DR

This paper explores how keV sterile neutrinos within composite neutrino models can serve as warm dark matter, produced either via resonant mechanisms or entropy-diluted thermal freeze-out, influenced by confinement dynamics.

Contribution

It demonstrates that composite neutrino theories naturally yield keV sterile neutrinos with suitable properties for warm dark matter production, highlighting new production mechanisms.

Findings

Sterile neutrinos can be resonantly produced as WDM in composite models.

Entropy production from confinement enables thermal freeze-out WDM.

Supercooling enhances entropy production for WDM viability.

Abstract

Elementary keV sterile Dirac neutrinos can be a natural ingredient of the composite neutrino scenario. For a certain class of composite neutrino theories, these sterile neutrinos naturally have the appropriate mixing angles to be resonantly produced warm dark matter (WDM). Alternatively, we show these sterile neutrinos can be WDM produced by an entropy-diluted thermal freeze-out, with the necessary entropy production arising not from an out-of-equilibrium decay, but rather from the confinement of the composite neutrino sector, provided there is sufficient supercooling.