Freeze-in dark matter and leptogenesis: a ψ 'SM route

We investigate the possibility of freeze-in dark matter production and baryogenesis via leptogenesis in a ψ ' ψ ′ SM model, which is an E₆ E 6 extension of the Standard Model, featuring a residual U(1)ψ ' U ( 1 ) ψ ′ gauge symmetry. This symmetry arises from a linear combination of U(1)_χ U ( 1 ) χ and U(1)ψ U ( 1 ) ψ , both of which are subgroups of the E₆ E 6 . The spontaneous breaking of U(1)ψ ' U ( 1 ) ψ ′ symmetry governs the dynamics of a singlet fermion, which serves as a freeze-in dark matter candidate. The dark matter mass arises from dimension-five operators, and a discrete symmetry ensures its stability. We show that freeze-in production from scalar decay can yield the correct relic abundance for dark matter masses between a few MeV to a few hundred GeV. Simultaneously, heavy right-handed neutrinos generate light neutrino masses via the type-I seesaw and produce the observed baryon asymmetry via leptogenesis.