Multi-Component Dark Matter: the vector and fermion case

TL;DR

This paper introduces a minimal UV-complete multi-component dark matter model with vector and fermion particles, analyzing its relic abundance, interactions, and potential for solving dark matter puzzles through complex dark sector dynamics.

Contribution

It presents a novel vector-fermion dark matter model with a detailed numerical analysis of relic abundance and interaction phenomena, extending standard single-component frameworks.

Findings

The model includes stable vector and fermion dark matter candidates.

Dark sector interactions like semi-annihilations significantly influence relic abundance.

Enhanced self-interactions are possible within the model.

Abstract

Multi-component dark matter scenarios constitute natural extensions of standard single-component setups and offer attractive new dynamics that could be adopted to solve various puzzles of dark matter. In this work we present and illustrate properties of a minimal UV-complete vector-fermion dark matter model where two or three dark sector particles are stable. The model we consider is an extension of the Standard Model (SM) by spontaneously broken extra $U(1)_X$ gauge symmetry and a Dirac fermion. All terms in the Lagrangian which are consistent with the assumed symmetry are present, so the model is renormalizable and consistent. To generate mass for the dark-vector $X_\mu$ the Higgs mechanism with a complex singlet $S$ is employed in the dark sector. Dark matter candidates are the massive vector boson $X_\mu$ and two Majorana fermions $\psi_\pm$. All the dark sector fields are singlets under the SM gauge group. The set of three coupled Boltzmann equations has been solved numerically and discussed. We have performed scans over the parameter space of the model implementing the total relic abundance and direct detection constraints. The dynamics of the vector-fermion dark matter model is very rich and various interesting phenomena appear, in particular, when the standard annihilations of a given dark matter are suppressed then the semi-annihilations, conversions and decays within the dark sector are crucial for the evolution of relic abundance and its present value. Possibility of enhanced self-interaction has been also discussed.