Resonant leptogenesis in minimal $U(1)_X$ extensions of the Standard Model

Abstract

We investigate a general $U(1)_X$ scenario where we introduce three generations of Standard Model (SM) singlet Right Handed Neutrinos (RHNs) to generate the light neutrino mass through the seesaw mechanism after the breaking of $U(1)_X$ and electroweak symmetries. In addition to that, a general $U(1)_X$ scenario involves an SM-singlet scalar field and due to the $U(1)_X$ symmetry breaking the mass of a neutral beyond the SM (BSM) gauge boson $Z^\prime$ is evolved. The RHNs, being charged under $U(1)_X$ scenario, can explain the origin of observed baryon asymmetry through the resonant leptogenesis process. Applying observed neutrino oscillation data we study $Z^\prime$ and BSM scalar induced processes to reproduce the observed baryon asymmetry. Hence we estimate bounds on the $U(1)_X$ gauge coupling $(g_X)$ and the mass of the $Z^\prime$ $(M_{Z^\prime})$ for different $U(1)_X$ charges and benchmark masses of RHN and SM-singlet scalar. Finally we compare our results with limits obtained from the existing limits from LEP-II and LHC. We find that depending on the $U(1)_X$ charges, the masses of RHNs and SM-singlet scalar resonant leptogenesis could provide stronger limit on $g_X$ for $M_{Z^\prime} > 5.8$ TeV which could be probed by high energy scattering experiment in future.