A $Z_4$ symmetric inverse seesaw model for neutrino masses and FIMP dark matter

Abstract: A theoretical framework based on a spontaneously broken $Z_4$ symmetry is proposed to generate neutrino masses via the inverse seesaw mechanism and to facilitate dark matter production through a freeze-in scenario. The model introduces right-handed neutrinos $N_i$, additional fermions $\chi_i$, and a complex scalar $S$. The stability of the dark matter candidate is ensured by an unbroken $Z_2$ subgroup, and its relic abundance is predominantly produced through decay and scattering processes involving the heavy singlet fermions. Phenomenological analyses show that this relatively minimal construction naturally aligns the neutrino oscillation parameters with the latest global oscillation data. Furthermore, the observed dark matter relic density is successfully accounted for within the overlapping parameter space relevant to neutrino properties.