Inverse seesaw accompanied by Dirac fermionic dark matter

Abstract

We present an inverse seesaw mechanism by resorting to a U(1)B−L gauge symmetry. In order to cancel the gauge anomalies, we introduce nine neutral fermions among which six participate in the inverse seesaw, while the other three form a Dirac fermion and a massless fermion. In this inverse seesaw, three neutral fermions are the usual right-handed neutrinos while the other three have a small Majorana mass term. An additional seesaw mechanism for generating these small Majorana masses also explains the cosmic baryon asymmetry in association with the sphaleron processes. The Dirac fermion becomes a stable dark matter while the massless fermion decouples early.