Abstract
Relic density calculations of dark matter freezing out from the primordial plasma have reached a high level of sophistication, with several numerical tools readily available that match the observationally required accuracy. Dark matter production via the freeze-in mechanism, on the other hand, is sensitive to much higher temperatures than in the freeze-out case, implying both technical and computational difficulties when aiming for the same level of precision. We revisit the formulation of freeze-in production in a way that facilitates the inclusion of in-medium corrections like plasma effects and the spin statistics of relativistic quantum gases, as well as the temperature dependence of dark matter production rates induced by the electroweak and strong phase transitions, and we discuss in detail the additional complications arising in the presence of s-channel resonances. We illustrate our approach in the context of Higgs portal models, and provide the most accurate calculation to date of the freeze-in abundance of Scalar Singlet dark matter. We explore in particular the case of small reheating temperatures, for which the couplings implied by the freeze-in mechanism may be testable at the LHC. Together with this article we present a major update 6.3 of DarkSUSY with the added capability of performing general freeze-in calculations, including all complications mentioned above.
Highlights
Various public numerical codes, such as DarkSUSY [2], micrOmegas [3] and MadDM [4] have been developed to automate the relic density calculation even in complicated scenarios, including for example co-annihilations, thresholds and resonances
We revisit the formulation of freeze-in production in a way that facilitates the inclusion of in-medium corrections like plasma effects and the spin statistics of relativistic quantum gases, as well as the temperature dependence of dark matter production rates induced by the electroweak and strong phase transitions, and we discuss in detail the additional complications arising in the presence of s-channel resonances
In many models of freeze-in there may even be a dependence on initial conditions, such as the details of reheating [11,12,13,14,15]. At such high temperatures a number of new effects become relevant, in-medium corrections like plasma effects [16,17,18,19,20] and the spin statistics of relativistic quantum gases [3, 21], as well as phase transitions, which can fundamentally change the relevant degrees of freedom of the theory under consideration [22, 23]
Summary
We start with a general description of the freeze-in process [5], i.e. the thermal production of DM particles with interaction strengths too weak to ever equilibrise with the heat bath. To keep the discussion general, we allow for both, DM particles χ and heat bath (SM) particles ψ, to have arbitrary mass and spin. We put special emphasis on the fact that the DM production from the heat bath through 2 → 2 processes, ψψ → χχ, can equivalently be described in terms of the annihilation of a would-be thermal population of DM particles, χχ → ψψ. This formal equivalence holds when assuming Maxwell-Boltzmann distributions — as familiar from cold DM freeze-out scenarios [32] — but even when fully taking into account the effect of quantum statistics in the phase-space distributions of the involved particles
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
