We generalize models invoking a spin-2 particle as a mediator between the dark sector and the standard model. We show that a massive spin-2 messenger can efficiently play the role of a portal between the two sectors. The dark matter is then produced via a freeze-in mechanism during the reheating epoch. In a large part of the parameter space, production through the exchange of a massive spin-2 mediator dominates over processes involving a graviton with Planck suppressed couplings. We perform a systematic analysis of such models for different values of the spin-2 mass relative to the maximum and the final temperature attained at reheating.
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The authors acknowledge M. Crisostomi for useful discussions. This work was supported by the France-US Projet International de Coopération Scientifique (PICS) Grant No. 06482, PICS MicroDark and the European Research Council (ERC) advanced grants Higgs@LHC. M. Dutra acknowledges support from the Brazilian PhD program “Ciências sem Fronteiras” Conselho Nacional de Desenvolvimiento cientifico e Tecnologico (CNPQ) Grant No. 202055/2015-9. N. Bernal and Y. Mambrini acknowledge partial support from the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Research and Innovation Staff Exchange (RISE) InvisiblesPlus (Grant No. 690575) and the Innovative Training Networks (ITN) Elusives (Grant No. 674896). N. B. is also supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under Grant No. FPA2017-84543-P and by the Universidad Antonio Nariño Grant No. 2017239. The work of K. A. O. and M. P. was supported in part by Department of Energy (DOE) Award No. DE–SC0011842 at the University of Minnesota.