Viability of Boosted Light Dark Matter in a Two-Component Scenario

TL;DR

This paper explores a two-component dark matter model with boosted light scalar and fermionic particles, analyzing their relic densities, interactions, and potential detectability within extended Higgs and vectorlike lepton frameworks.

Contribution

It introduces a novel two-component dark matter scenario with boosted light scalar DM and fermionic DM, including model extensions to satisfy experimental constraints and analyze relic densities.

Findings

Broader fermionic DM mass region due to annihilation channel

Scalar DM relic density increases with boost effects

Significant parameter space where total DM relic is fermion-dominated

Abstract

We study the boosted dark matter (BDM) scenario in a two-component model. We consider a neutrinophilic two-Higgs doublet model ($\nu$2HDM), which consists of one extra Higgs doublet and a light right-handed neutrino. This model is extended with a light ($\sim 10$~MeV) singlet scalar DM $\phi_3$, which is stabilized under an extra dark $Z_2^{\rm DM}$ symmetry and can only effectively annihilate through the CP even scalar $H$. Although oblique parameters put tight constraints on the model, introduction of vectorlike leptons (VLL) can potentially salvage the issue. The vectorlike doublet $N$ and singlet $\chi$ are also stabilized through dark $Z_2^{\rm DM}$ symmetry. The lightest vectorlike mass eigenstate ($\chi_1 \sim 100$~GeV) is the 2nd DM component of the model. The fermion DM is restricted in a narrow mass region while a somewhat broader mass region is allowed for the scalar DM. However, when two DM sectors are coupled, the annihilation channel $\chi_1 \chi_1 \to \phi_3 \phi_3$ opens up. As a result, the fermionic relic density decreases, and paves way for broader fermionic DM mass region with under-abundant relic: a region of $[30-65]$ GeV compared to a narrower $[40-50]$ GeV window for the single component case. On the other hand, the light DM $\phi_3$ acquires significant boost from the annihilation of $\chi_1$, causing a dilution in the resonant annihilation of $\phi_3$. This in turn increases the scalar DM relic, allowing for a smaller mass region compared to the individual case. The exact and underabundant relic is achievable in a significant parameter space of the two-component model where the total DM relic is mainly dominated by the fermionic DM contribution. The scalar DM is found to be sub-dominant or equally dominant ($\sim 30 \% - 80 \%$ of total DM) with significant boost which can be detected in experiments.