Item

Abstract

In this thesis, an extra-dimensional model for Dark Matter is studied. The Dark Matter is assumed to be a massive scalar particle interacting only gravitationally in the extra-dimensional Randall-Sundrum scenario. The annihilation of Dark Matter into Kaluza-Klein (KK) modes, Radions and Standard Model particles is analyzed. Denoting with s the centre of mass energy squared of the process, the amplitudes for to the production of KK-modes are found to be of O(s^3). Such a growth would imply a breakdown of the theory at scales much lower than its fundamental scale. This type of issue is well known in massive gravity and there is no general solution to it. It is here proved analytically that in the Randall-Sundrum scenario, this anomalous growth in energy is reduced to O(s) once the contributions of all KK-modes and of the Radion are taken into account and summed properly. Studying the relic abundance of Dark Matter in the context of the freeze-out mechanism, we find that the allowed parameter space of the theory is much smaller than what had been found previously in the literature. Lastly, the bounds, derived from the data of diphoton production from LHC Run II, are considered.