Dark branes for dark matter

Abstract

We propose a setup for the origin of dark matter based on spacetime with a warped extra dimension and three branes: the Planck brane, the TeV brane, at a (few) TeV scale ρT, and a dark brane, at a (sub-)GeV scale ρ1≲100  GeV≪ρT. The Standard Model (SM) is localized in the TeV brane, thus solving the Higgs hierarchy problem, while the dark matter χ, a Dirac fermion with mass mχ<ρ1, is localized in the dark brane. The radion, with mass mr<mχ, interacts strongly [∼mχ/ρ1∼O(1)] with dark matter and very weakly (∼mfρ1/ρT2≪1) with the Standard Model matter f. The generic conflict between the bounds on its detection signatures and its proper relic abundance is avoided as dark matter annihilation is p-wave suppressed. The former is determined by its very weak interactions with the SM and the latter by its much stronger annihilation into radions. Therefore, there is a vast range in the dark matter’s parameter space where the correct relic abundance is achieved consistently with the existing bounds. Moreover, for the dark brane with ρ1≲3  GeV, a confinement/deconfinement first order phase transition, where the radion condensates, produces a stochastic gravitational wave background at the nanohertz frequencies, which can be identified with the signal detected by the Pulsar Timing Array (PTA) experiments. In the PTA window, for 0.15≲mχ≲2  GeV the relic abundance is reproduced and all constraints are satisfied. Published by the American Physical Society 2024