Quantum and thermal corrections to dark matter annihilation

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As dark matter observation and detection capabilities become more precise and more diverse, theoretical calculations based on tree-level annihilation are often no longer sufficient. The proposed project focuses on dark matter processes and models where loop effects are important. In the absence of definitive non-gravitational evidence of dark matter, the goal is not so much on precision physics, but on quantum effects, which are large and result in order one or qualitative modifications of dark matter annihilation. These affect the freeze-out of the relic abundance of dark matter particles in the early Universe through the Sommerfeld effect, as well as dark matter annihilation today. Here the Sommerfeld effect and large electroweak logarithms as well as electroweak gauge-boson radiation may result in modifications of photon, neutrino and charged-particle spectra detectable in cosmic rays. The project addresses these loop effects through methods more familiar from collider physics (effective field theory, renormalization-group evolution, resummation techniques) and combines them with dark matter phenomenology. It focuses mainly on heavy weakly interacting dark matter particles (WIMPs) with mass larger than the electroweak scale, where the above effects are large. In addition, the influence of the hot thermal plasma on the freeze-out process will be investigated. For generic dark matter annihilation these investigations are of purely theoretical interest and clarify fundamental questions of infrared finiteness. However, this is no longer the case when parts of the annihilation process are sensitive to scales commensurate with the temperature of the plasma, as is the case for the Sommerfeld effect.