Low Scale Leptogenesis and Dark Matter Candidates in an Extended Seesaw Model

TL;DR

This work extends the seesaw mechanism by adding extra singlet neutrinos S and a singlet scalar Phi, enabling low-scale leptogenesis at TeV scales and offering two dark matter candidates. A Z2 symmetry stabilizes the dark sector, while Higgs-portal and S–Φ interactions drive both leptogenesis and dark matter phenomenology. The relic abundance can be achieved via coannihilation and Higgs-mediated annihilation, with distinct viable regions for S and Φ depending on the Higgs mass; direct-detection constraints from XENON10 and LHC Higgs-portal signatures (including invisible decays) provide experimental handles to probe or constrain the model. The analysis highlights how a common origin for baryogenesis and dark matter can be tested through collider and direct-detection experiments, offering distinctive predictions relative to self-interacting dark matter scenarios.

Abstract

We consider a variant of seesaw mechanism by introducing extra singlet neutrinos and singlet scalar boson, and show how low scale leptogenesis is successfully realized in this scenario. We examine if the newly introduced neutral particles, either singlet Majorana neutrino or singlet scalar boson, can be a candidate for dark matter. We also discuss the implications of the dark matter detection through the scattering off the nucleus of the detecting material on our scenarios for dark matter. In addition, we study the implications for the search of invisible Higgs decay at LHC, which may serve as a probe of our scenario for dark matter.

Figures (9)

• Figure 1: Diagrams contributing to the lepton asymmetry.
• Figure 2: Cascade decays of NOP to LOP : (a) case for $m_S < m_{\Phi}$, (b) case for $m_{\Phi}< m_S$
• Figure 3: Diagram for annihilation processes of the singlet scalar bosons $\Phi$
• Figure 4: Relationship between $\lambda$ and $m_S$ arisen from the constraints $\Omega_S h^2 = 0.128$ and $0.094$ corresponding to the upper and lower limit of $\Omega_{DM}h^2$ measured from WMAP, respectively. Here the mass difference $\delta m = m_{\Phi} -m_S$ has been taken to be 5 GeV and Higgs mass $m_h$ to be (a) $120\, \hbox{GeV}$ and (b) $200\, \hbox{GeV}$. Here the shadowed region is forbidden due to the breakdown of perturbation.
• Figure 5: Relationship between $\lambda$ and $m_{\Phi}$ corresponding to $\Omega_\Phi h^2 =0.128$ (the lower solid line) and 0.094 (the upper solid line), respectively. The mass difference $\delta m = m_S -m_\Phi$ has been taken to be 5 GeV and $m_h$ to be (a) 120 GeV and (b) 200 GeV. Here the shadowed region is forbidden due to breakdown of perturbation and the dashed line corresponds to the prediction of the model with a self-interacting dark matter sh for $\Omega_\Phi h^2 = 0.128$.