Dark Matter Capture by the Sun via Self-Interaction

Abstract

There is compelling evidence that dark matter constitutes 85 % of the universe's total matter content. So far, this distinctly different type of particle is observed only in terms of its gravitational effects, but various detection experiments are conducted and underway. One method is indirect detection of neutrinos coming from the Sun. Under the assumption that dark matter consists of Weakly Interacting Massive Particles (WIMPs), one of the most studied dark matter particle candidates, these WIMPs would interact with atomic nuclei within the Sun and be trapped in its gravitational field. After a large enough concentration of trapped WIMPs has been amassed, they would begin annihilating with each other, producing a high-energy neutrino signal. In this thesis I study the possibility that WIMP self-interaction has a significant effect on the total capture rate and resulting neutrino signal. Potentially, an amassed concentration of WIMPs inside the Sun can itself constitute a scattering target and contribute to further captures from the galactic dark matter halo. In order to describe the kinematics of particle interaction and WIMP capture I utilize an effective field theory in the non-relativistic limit. This allows me to explore, in a model-independent way, the parameter space of interaction and the possibility for WIMP capture enhancement due to self-interaction. Upper limits to the strength of these interactions come from direct detection experiments and galaxy cluster observation and simulation. It is found that self-interaction could play a significant role in amplifying the neutrino signal; even an amplification of several orders of magnitude is not ruled out by current limits.