We identify and analyze thermal dark matter candidates in the fraternal twin
Higgs model and its generalizations. The relic abundance of fraternal twin dark
matter is set by twin weak interactions, with a scale tightly tied to the weak
scale of the Standard Model by naturalness considerations. As such, the dark
matter candidates benefit from a "fraternal WIMP miracle," reproducing the
observed dark matter abundance for dark matter masses between 50 and 150 GeV.
However, the couplings dominantly responsible for dark matter annihilation do
not lead to interactions with the visible sector. The direct detection rate is
instead set via fermionic Higgs portal interactions, which are likewise
constrained by naturalness considerations but parametrically weaker than those
leading to dark matter annihilation. The predicted direct detection cross
section is close to current LUX bounds and presents an opportunity for the next
generation of direct detection experiments.Comment: 22 pages, 6 figures. v2: Relic abundance calculations revised and
improved, citations added. Conclusions largely unchanged. v3: Minor changes,
accepted by JCA
