We propose a complete $R$-parity violating supersymmetric model with baryon triality that contains a Dine-Fischler-Srednicki-Zhitnitsky axion chiral superfield. We parametrize supersymmetry breaking with soft terms and determine under which conditions the model is cosmologically viable. As expected we always find a region of parameter space in which the axion is a cold dark matter candidate. The mass of the axino, the fermionic partner of the axion, is controlled by a Yukawa coupling. When heavy [$\mathcal{O}(\mathrm{TeV})$], the axino decays early and poses no cosmological problems. When light [$\mathcal{O}(\mathrm{keV})$], it can be long lived and a warm dark matter candidate. We concentrate on the latter case and study in detail the decay modes of the axino. We find that constraints from astrophysical x rays and gamma rays on the decay into photon and neutrino can set new bounds on some trilinear supersymmetric $R$-parity violating Yukawa couplings. In some corners of the parameter space the decays of a relic axino can also explain a putative 3.5 keV line.

• Received 31 August 2018

DOI:https://doi.org/10.1103/PhysRevD.99.015003

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society