On the minimal mass of thermal dark matter and the viability of millicharged particles affecting 21cm cosmology

Autor(en): Xiaoyong Chu, Josef Pradler
Abstrakt: Thermal freeze-out offers an attractive explanation of the dark matter density free from fine-tuning of initial conditions. For dark matter with a mass below tens of MeV, photons, electrons, and neutrinos are the only available direct Standard Model annihilation products. Using a full three-sector abundance calculation, we determine the minimal mass of dark matter, allowing for an arbitrary branching into electrons/photons and neutrinos that is compatible with current cosmological observations. The analysis takes into account the heat transfer between the various sectors from annihilation and elastic scattering, representing the first fully self-consistent analysis that tracks the respective sectors' temperatures. We thereby provide accurate thermal annihilation cross sections, particularly for velocity-dependent cases, and deduce the sensitivity of current and upcoming CMB experiments to MeV thermal dark matter. In the latter context, we also establish the fine-tuned parameter region where a tiny admixture of neutrinos in the final states rules in MeV-scale $p$-wave annihilating DM into electrons. Finally, we show that a sub-% millicharged dark matter with an interaction strength that interferes with 21~cm cosmology is still allowed when freeze-out is supplemented with annihilation into neutrinos. For all cases considered, we provide concrete particle physics models and supplement our findings with a discussion of other relevant experimental results.
Organisation(en): Teilchenphysik
Externe Organisation(en): Österreichische Akademie der Wissenschaften (ÖAW)
Publikationsdatum: 10-2023
ÖFOS 2012: 103036 Theoretische Physik
Schlagwörter
Link zum Portal: https://ucris.univie.ac.at/portal/de/publications/on-the-minimal-mass-of-thermal-dark-matter-and-the-viability-of-millicharged-particles-affecting-21cm-cosmology(8a4741bf-f384-4aa8-8efa-afb563017b8b).html