Freeze-In Dark Matter and Leptogenesis: a $ψ'$SM route

Abstract

We investigate the possibility of \emph{freeze-in} dark matter production and baryogenesis via leptogenesis in a $ψ'$SM model, which is an $E_6$ extension of the Standard Model, featuring a residual $U(1)_{ψ'}$ gauge symmetry. This symmetry arises from a linear combination of $U(1)_χ$ and $U(1)_ψ$, both of which are subgroups of the $E_6$. The spontaneous breaking of $U(1)_{ψ'}$ symmetry governs the dynamics of a singlet fermion, which serves as a freeze-in dark matter candidate. The dark matter mass arises from dimension-five operators, and a discrete symmetry ensures its stability. We show that freeze-in production from scalar decay can yield the correct relic abundance for dark matter masses between a few MeV to a few hundred GeV. Simultaneously, heavy right-handed neutrinos generate light neutrino masses via the type-I seesaw and produce the observed baryon asymmetry via leptogenesis.

Figures (2)

• Figure 1: Left panel: Solutions to Eq. \ref{['BE_FIMP']} for evolution of $Y_{\mathcal{N}_{\rm DM}}$ for two benchmark points discussed in Table \ref{['tab2']}. Right Panel: Relic density allowed parameter space in $M_{\rm DM}-v_{\psi'}$ bi-dimensional plane for $M_{\mathcal{N}} = 10^2~\rm{ GeV}$, $10^4~\rm{ GeV}$ and $10^6~\rm{ GeV}$. The colored region on the left shows the parameter space where the DM can be thermalized, the colored region on the right corresponds to $\Lambda>M_{\rm Pl}$, While the colored region in the top is disallowed from the kinematic condition $M_\mathcal{N}<2 M_{\rm DM}$, the one at the bottom is excluded from the Lyman-$\alpha$ bound.
• Figure 2: Solutions to BEQs (Eq. \ref{['eq:be_asymm']}) for evolution of $Y_{N_1}$ (black), and lepton asymmetry $Y_{\Delta L}$ (orange). The gray dashed line indicates the correct $Y_{\Delta L}$ is required to produce the observed baryon asymmetry of the Universe. Here we have set $z_R=0.05 -0.9i$.