A singlet scalar assisted $N_2$ Leptogenesis and Pseudo-Scalar Dark Matter

Abstract

We study the Leptogenesis and Dark Matter in the presence of an extra singlet complex scalar field in an extended discrete ${\mathcal{Z}}_3$ symmetry. The vacuum expectation value of the new scalar spontaneously breaks the ${\mathcal{Z}}_3$ symmetry. A remnant CP-like ${\mathcal{Z}}_2$ symmetry stabilizes the imaginary part of the complex scalar field which can act as a pseudo-Goldstone DM. The real part of the complex scalar couples to RHN opens up new decay channels which can lead to a larger CP-violation in generating the lepton asymmetry. Thus the singlet complex scalar plays a crucial role in understanding the Leptogenesis and Dark Matter parameter space. This singlet complex scalar is also responsible for the First-Order Phase Transition (FOPT) which may provide observable stochastic Gravitational wave signatures. We discuss the possible correlations among these three phenomena.

Comments: Published in EPJC