Cosmological implications of a B-L charged hidden scalar:leptogenesis and gravitational waves

In this study, we investigated the cosmological implications of a complex singlet scalar S with non-trivial B-L charges in the conformal U(1)B-L theory. It was found that, in a sizable region of parameter space, S may disturb the resonant leptogenesis mechanism, which is used to generate baryon asymmetry, and affect the symmetry breaking dynamics in the strong first order phase transition. The stochastic gravitational waves(GWs) produced at the phase transition can be probed in future GW experiments. The GW searches prefer a relatively light S at the TeV-scale; however, this is difficult to detect directly at future high-energy colliders.