Realization of Self-interacting Dark Matter via Freeze-In

We examine dark matter in the context of singlet-doublet model, a simple extension of the Standard model by a \(SU(2)_L\) singlet ( \(\chi \) ) and a \(SU(2)_L\) vector doublet ( \(\Psi \) ) fermion. Here, we discuss a picture where the production of fermion dark matter occurs via freeze-in. In addition, the light scalar mediator present in our framework can mediate significant self-interaction for the fermion dark matter. Such large self-interaction can solve the small-scale structure anomalies of the Universe. Interestingly, the fast expansion in the early Universe helps to realize self-interacting dark matter in case of freeze-in production.