A warped scalar portal to fermionic dark matter

TL;DR

This paper proposes a model with warped extra dimensions and a scalar portal that naturally explains fermionic dark matter, modifies Higgs interactions, and explores dark matter relic abundance in different cosmological scenarios.

Contribution

It introduces a warped extra dimension model with a Z2-odd scalar singlet that acts as a portal for fermionic dark matter and analyzes its implications for Higgs couplings and relic abundance.

Findings

Scalar excitations mix with the Higgs, affecting its couplings.

Scalar portal can facilitate fermionic dark matter coannihilation.

Model remains viable in both freeze-out and early matter domination scenarios.

Abstract

We argue that extensions of the SM with a warped extra dimension, together with a new $\mathbb{Z}_2$-odd scalar singlet, provide a natural explanation not only for the hierarchy problem but also for the nature of fermion bulk masses and the observed dark matter relic abundance. In particular, the Kaluza-Klein excitations of the new scalar particle, which is required to naturally obtain fermion bulk masses through Yukawa-like interactions, can be the leading portal to any fermion propagating into the bulk of the extra dimension and playing the role of dark matter. Moreover, such scalar excitations will necessarily mix with the Higgs boson, leading to modifications of the Higgs couplings and branching ratios, and allowing the Higgs to mediate the coannihilation of the fermionic dark matter. We study these effects and explore the viability of fermionic dark matter in the presence of these new heavy scalar mediators both in the usual freeze-out scenario and in the case where the freeze-out happens during an early period of matter domination.