2024/09/13 by Partha Kumar Paul, Paul, Partha Kumar, Narendra Sahu +3 · 3 citations
Physics and Astronomy · Computer Science · #Cosmology and Gravitation Theories #Scientific Research and Discoveries #Computational Physics and Python Applications
paper · pdf · doi:10.48550/arxiv.2409.08828
In a canonical type-I seesaw scenario, the Standard Model is extended with three singlet right-handed neutrinos (RHNs) Ni, i=1,2,3 with masses Mi, i=1,2,3 to simultaneously explain sub-eV masses of light neutrinos and baryon asymmetry of the Universe at high scales. In this paper, we show that a relatively low-scale thermal leptogenesis accompanied by gravitational wave signatures is possible when the type-I seesaw is extended with a singlet fermion (S) and a singlet scalar (ρ), where S and ρ are odd under a discrete Z2 symmetry. We also add a vectorlike fermion doublet Ψ and impose a Z^′2 symmetry under which both N1 and Ψ are odd while all other particles are even. This gives rise to a singlet-doublet Majorana fermion dark matter in our setup. At a high scale, the Z2 symmetry is broken spontaneously by the vacuum expectation value of ρ and leads to (i) mixing between RHNs (N2, N3) and S, and (ii) formation of Domain walls (DWs). In the former case, the final lepton asymmetry is generated by the out-of-equilibrium decay of S, which dominantly mixes with N2. We show that the scale of thermal leptogenesis can be lowered to MS ∼ 2 × 106 GeV, which is 3 orders of magnitude lower than the thermal leptogenesis in canonical type-I seesaw. In the latter case, the disappearance of the DWs gives observable gravitational wave signatures, which can be probed at LISA, DECIGO, \rm μARES etc.