DESY Theory Seminar

# Light Axinos from Freeze-in: production processes, phase space distributions, and Ly-alpha constraints

 Description While decaying 7 keV dark matter (DM) is one of the most promising explanations of the 3.5 keV line excess, it is usually in tension with Ly-alpha forest observations when DM particles are produced from the thermal plasma. In this talk, we consider freeze-in production of axino DM in the supersymmetric (SUSY) Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) model in order to resolve this tension. Interestingly, freeze-in production of axinos results in a colder phase space distribution than the thermal one. By directly comparing the linear matter power spectra with Ly-alpha forest constraints, we demonstrate to what extent the tension with the Ly-alpha forest data can be mitigated. We introduce benchmark points with Higgsino next-to-light supersymmetric particle (NLSP) and wino NLSP. In the case of Higgsino NLSP, the most stringent Ly-alpha forest constraint can be evaded with mild entropy production from saxion decay inherent in the SUSY DFSZ axion model.