Phenomenology of Dark Matter from Radio to Gamma Ray Frequencies

Multiwavelength astronomical observations have been proven to be of crucial relevance in understanding the most fundamental questions in physics. One of the biggest mysteries of nature is the existence of a (still) unidentified type of matter that makes up most of the material universe. Although little is known about its nature, it is very likely that this exotic Dark Matter (DM) is made of so-called Weakly Interacting Massive Particles(WIMPs).In this thesis we investigate which strategies can best address the fundamental question: What is Dark Matter? Specifically, by following the “WIMP” paradigm as our guiding principle, we comprehensively discuss the phenomenology of prospective “indirect” detection scenarios of such WIMPs. Special consideration is given to extraterrestrial gamma rays and radio waves produced around the center of the Milky Way. In light of two recently highly debated claims of WIMP Dark Matter discovery, namely the 130 GeV gamma-ray line and the GeV gamma-ray excess, we invoke ourmethods to confront those hypotheses. In addition our study contains antiparticle cosmic-ray (antiproton and positron) data analyses. The phenomenology for indirect DM detection with these “messengers” is briefly discussed as well.By exploiting the high degree of symmetry of typical annihilating 2-WIMP initial states, we are able to employ a very powerful tool in theoretical particle physics: the generalized optical theorem. This theorem relates the amplitude of loop-suppressed processes, such as the 130 GeV line if interpreted as product of WIMP annihilations, with tree-level process which are constrained in the same way as with the GeV excess. Unprecedentedly reported analytical computations of partial-wave (and helicity) cross sections with general applicability are calculated and applied.The possibility that a non-trivial effect in the particle model for DM might enhance the strength of a gamma-ray line signal is also explored. We focus on the five-dimensional model with “Universal Extra Dimensions” (UED) which offers a suitable DM candidate. We show that the intrinsic resonant properties of the model give rise to enhancements in the annihilation cross sections. All the necessary couplings of KK-number violating vertices localized in the orbifold fixed points are also computed for the first time.Motivated by the possibility that black holes can accelerate DM particles up to, in principle, arbitrarily large energies, we investigate WIMP annihilations with larger center-of-mass energies in the UED context