Abstract
We revisit the case of scalar Dark Matter interacting just gravitationally with the Standard Model (SM) particles in an extra-dimensional Randall-Sundrum scenario. We assume that both, the Dark Matter and the Standard Model, are localized in the TeV brane and only interact via gravitational mediators, namely the graviton Kaluza-Klein modes and the radion. We analyze in detail the dark matter annihilation channel into two on-shell KK-gravitons, and contrary to previous studies which overlooked this process, we find that it is possible to obtain the correct relic abundance for dark matter masses in the range [1, 10] TeV even after taking into account the strong bounds from LHC Run II. We also consider the impact of the radion contribution (virtual exchange leading to SM final states as well as on-shell production), which does not significantly change our results. Quite interestingly, a sizeable part of the currently allowed parameter space could be tested by LHC Run III and by the High-Luminosity LHC.
Highlights
The Nature of Dark Matter (DM) is one of the long-standing puzzles that still have to be explained in order to claim that we have a “complete” picture of the Universe
In the appendices we give some of the mathematical expressions used in the paper: appendix A contains the KK-graviton propagator and polarization tensor; in appendix B we provide the Feynman rules for our model; in appendix C we give the expressions for the decay amplitudes of the KK-graviton and of the radion; and, eventually, in appendix D we give the formulæ for the annihilation cross-sections of dark matter particles into Standard Model particles, KK-gravitons and radions
In ref. [19] two additional setups where analyzed and confronted with indirect bounds from astrophysical data: model A, which addresses the hierarchy problem with the Higgs and DM localized on the IR-brane and the Standard Model (SM) matter on the UV-brane, and model B where only DM is localized on the IR-brane while the SM matter and Higgs fields are confined to the UV-brane
Summary
The Nature of Dark Matter (DM) is one of the long-standing puzzles that still have to be explained in order to claim that we have a “complete” picture of the Universe. The paper is organized as follows: in section 2 we outline the theoretical framework, reminding shortly the basic ingredients of warped extra-dimensional scenarios and of how dark matter can be included within this hypothesis; in section 3 we show our results for the annihilation cross-sections of scalar DM particles into SM particles, KK-gravitons and/or radions; in section 4 we review the present experimental bounds on the Kaluza-Klein graviton mass from LEP and LHC, as well as on the DM mass from direct and indirect search experiments, and we remind the theoretical constraints coming from unitarity violation and effective field theory consistency; in section 5 we explore the allowed parameter space such that the correct relic abundance is achieved for scalar DM particles; and, eventually, in section 6 we conclude. Expressions for the decay amplitudes of the KK-graviton and of the radion; and, eventually, in appendix D we give the formulæ for the annihilation cross-sections of dark matter particles into Standard Model particles, KK-gravitons and radions
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