Dark Matter Phenomenology in an Extended Littlest Seesaw Model and Effects of Primordial Black Hole

We consider an extension of the Littlest Seesaw model with an additional scalar and a fermionic particle under the freeze-in scenario. Primordial black holes of a certain mass range can act as an alternate production mechanism for the dark matter particles as it evaporates via Hawking radiation. Furthermore, the presence of primordial black holes with substantial energy density give rise to non-standard cosmology which also modifies the freeze-in production. We have investigated this freeze-in scenario in presence of primordial black holes for a few interesting cases and constrained the parameter space accordingly. If the universe is primordial black hole dominated at any point before Big Bang Nucleosynthesis, we have found that the final relic in that case is constituted mostly by the evaporation component in the high dark matter mass and by the freeze-in component in the low dark matter mass.