Spin-dependence of Gravity-mediated Dark Matter in Warped Extra-Dimensions

Abstract

We study the spin-dependence of Dark Matter (DM) particles which interact gravitationally with the Standard Model (SM) in an extra-dimensional Randall-Sundrum scenario. We assume that both the Dark Matter and the Standard Model are confined to the TeV (Infra-red) brane and only interact via gravitational mediators, namely Kaluza-Klein gravitons and the radion. We analyze the different DM annihilation channels and find that it is possible to achieve the presently observed relic abundance of Dark Matter, $\Omega_{\rm DM}$, within the freeze-out mechanism for DM particles of spin 0, 1/2 and 1. We study the region of the model parameter space for which $\Omega_{\rm DM}$ is achieved and compare it with the different experimental and theoretical bounds. We also consider the impact of the radion in the phenomenology. We find that, for DM particles mass $m_{\rm DM} \in [1,15]$ TeV, most of the parameter space is excluded by the current constraints or will be excluded by the LHC Run III or by the LHC upgrade, the HL-LHC. The presence of the radion does not modify significantly the non-excluded region. The observed DM relic abundance can still be achieved for DM masses $m_{\rm } \in [4,15]$ TeV and $m_{G_1} < 10$ TeV for scalar and vector boson Dark Matter. On the other hand, for spin 1/2 fermion Dark Matter, only a tiny region with $m_{\rm DM } \in [4, 15]$ TeV, $m_{G_1} \in [5,10]$ TeV and $\Lambda > m_{G_1}$ is compatible with theoretical and experimental bounds.