Vector-like dark matter within an alternative left-right symmetric model

Abstract

We investigate an extension of the left-right symmetric model featuring an additional non-abelian $SU(2)$ gauge symmetry. The particle content is augmented by one generation of vector-like leptons transforming under the fundamental representation of this new gauge group. We demonstrate that the neutral component of the vector-like lepton multiplet naturally provides a viable and stable dark matter candidate. Stability is ensured by imposing a discrete parity symmetry that forbids mixing between the vector-like leptons and the Standard Model leptons. As a consequence, the dark sector interacts with the visible sector exclusively through the vector portal (via s-channel processes) and the vector-like lepton portal (via t-channel processes). In our analysis, we incorporate collider constraints on the mass of the first-generation extra charged gauge boson $W^{\prime\pm}$, while assuming that additional scalar states are decoupled from the relevant energy scale for simplicity. We identify the regions of parameter space consistent with the observed relic abundance, collider bounds on the charged partner $E^{\pm}$, current direct detection limits from the LZ experiment and indirect detection constraints from Fermi-LAT. We find viable dark matter with a mass at the TeV scale. We show the complementarity of direct and indirect searches in probing the remaining parameter space of the model, in particular comparing the prospects of multi-ton direct detection experiments such as XLZD and of the CTA telescope.

Figures (10)

• Figure 1: Feynman diagrams for the annihilation and co-annihilation processes via the vector boson/vector-like lepton portals. In addition to fermions in the final state, the s-channel processes (up diagrams) can involve gauge bosons and/or the Higgs in, see eq. (\ref{['final_states']}).
• Figure 2: $\Omega h^2$ variation w.r.t $m_N$ for several benchmark values of the gauge coupling $g_{_V}$.
• Figure 3: Feynman diagrams for the DM elastic scattering off nucleons.
• Figure 4: (Left panel) $\sigma_{SI}$ off proton and neutron variation w.r.t $g_{_V}$ for a benchmark value of $m_{N}=m_{W^{\prime}}/2=2$ TeV. (Right panel) $\sigma_{SI}$ off proton and neutron variation w.r.t $m_N$ for a benchmark value of $m_{W^{\prime}}=4$ TeV and several values of $g_{_V}$.
• Figure 5: $\xi\times\sigma_{SI}^{Xe}$ w.r.t $m_N$ for tow scenarios of mass splitting $\Delta_m=1$ GeV (TeV) and several benchmark values of $g_V$. The thick black line represent the current limits of LZ experiment LZ:2024zvo, the brown dashed lines represent the future projection limits of XLZD for exposures $200t\times y$ and $1000t\times y$Aalbers:2022dzr, where the orange dash-dotted one represents the neutrino floor Billard:2013qya. The inset in the left panel highlight the low mass region of DM for $\Delta_m=1$ GeV scenario.