Testable Flavored TeV-scale Resonant Leptogenesis with MeV-GeV Dark Matter in a Neutrinophilic 2HDM

TL;DR

The paper tackles the challenge of explaining the baryon asymmetry of the universe by embedding resonant leptogenesis in a neutrinophilic two-Higgs doublet model with three right-handed neutrinos. It proposes a mass pattern $M_1 \ll T_{\text{spha}} < M_2 \sim M_3$ and a mild degeneracy $\\Delta M_{32}/M_2 \sim \\mathcal{O}(10^{-3}-10^{-2})$ to enable TeV-scale leptogenesis while yielding a stable MeV–GeV $N_1$ that can act as dark matter. The analysis combines flavor-resolved CP asymmetries, density-matrix/ Boltzmann dynamics, and the Casas-Ibarra parametrization to map low-energy neutrino data to high-energy parameters, performing extensive numerical scans and identifying benchmark points that reproduce the observed BAU. The model predicts testable signatures at colliders, fixed-target experiments, and dark-matter detectors, and it offers a unified explanation for BAU, neutrino masses, and DM within a TeV-scale, experimentally accessible framework.

Abstract

We explore flavored resonant leptogenesis embedded in a neutrinophilic 2HDM. Successful leptogenesis is achieved by the very mildly degenerate two heavier right-handed neutrinos (RHNs), $N_2$ and $N_3$, with mass splitting of only $ΔM_{32}/M_2 \sim \mathcal{O}(0.1\%-1\%)$. The lightest RHN, with MeV-GeV-scale mass, lies below the sphaleron freeze-out temperature and remains stable, serving as a dark matter candidate. The model enables TeV-scale leptogenesis while avoiding the extreme mass degeneracy plagued conventional resonant leptogenesis. Baryon asymmetry, neutrino masses, and potentially the dark matter relic density can be addressed within a unified and experimentally testable framework.

Figures (6)

• Figure 1: Bounds on $M_2$ by $\Delta L = 2$ washout rate as a function of $v_2$. Locations of BM points for successful leptogenesis from Table \ref{['tab:BM_points_simple']} are also shown.
• Figure 2: BAU dependence as a contour on $\delta_\text{CP}$ and $\alpha_{21}$ plane. The color corresponds to the magnitude of $\eta_B$ survived. The boundary of red and orange corresponds to the observed value.
• Figure 3: BAU dependence as a contour on the mass of the lightest LH neutrino $m_{1(3)}$ and the mass of the lightest RH neutrino $M_1$.
• Figure 4: Scan contours for NO spectrum with $\tan\beta=225,\ 100$.
• Figure 5: Scan contours for IO spectrum with $\tan\beta=225,\ 100$.