Theory: Back to phase space: quasi thermal dark radiation

by Alessandro Lenoci

Monday 8 Jul 2024, 15:00 → 16:00 Europe/Berlin

SR2

Motivated by the stunning sensitivity of future CMB surveys, I will discuss how to precisely compute the  the amount of dark radiation produced in the early Universe by two-body decays or binary scatterings with thermal bath particles via a rigorous analysis in momentum space. This approach allows for studying light particles that never reach equilibrium across cosmic history, and to scrutinize the physics of the decoupling when they thermalize instead. We incorporate quantum statistical effects for all the particles involved in the production processes, and we account for the energy exchanged between the visible and invisible sectors. Non-instantaneous decoupling is responsible for spectral distortions in the final distributions. We undertake a comprehensive comparison between our exact results and approximated methods commonly employed in the existing literature.