Flipped $U(1)$ extended Standard Model and Majorana dark matter

We propose a general flavor-independent extension of the Standard Model (SM) with the minimal particle content, based on the symmetry $SU(3)_C\times SU(2)_L\times U(1)_{Y'}\times U(1)_X\times Z_2$. In this scenario, the charge operator is identified in terms of the charges of two $U(1)$ gauge symmetries. The light neutrino masses are generated via Type-I seesaw mechanism only with two heavy right-handed neutrinos acquiring their Majorana masses through the $U(1)_{Y'}\times U(1)_X$ symmetry breaking. We study various experimental constraints on the parameters of the model and investigate the phenomenology of the right-handed neutrino dark matter (DM) candidate assigned a $Z_2$-odd parity. We find that the most important constraints are the observed DM relic abundance, the current LHC limits, and the ambiguity of the SM neutral gauge boson mass.