Non-thermal Dark Matter in $U(1)_{B-L}$ Extension of Inert Doublet Model

Abstract

We propose an extension of the Inert Doublet Model (IDM) that explains both neutrino masses and dark matter (DM) in the intermediate-mass range by incorporating a $U(1)_{B-L}$ gauge symmetry. This additional symmetry enables the inclusion of right-handed neutrinos, providing a natural mechanism for neutrino mass generation. While the CP-even component of the inert doublet can serve as a DM candidate, its thermal relic abundance is insufficient to match the observed DM density. To address this, we introduce a non-thermal production mechanism, where a heavy scalar associated with the $U(1)_{B-L}$ symmetry decays into the inert doublet scalar, yielding a viable relic abundance at low reheating temperatures. We also examine both direct and indirect detection prospects for this DM candidate and assess the model against current experimental constraints.