Stealth Dark Matter: Dark scalar baryons through the Higgs portal

TL;DR

This paper introduces a new composite scalar dark matter model called Stealth Dark Matter, which naturally remains stable and interacts with the Higgs boson, with constraints derived from lattice simulations and collider data.

Contribution

The paper develops a novel SU(4) composite dark matter model with natural mass scales and automatic stability, analyzing its phenomenology and experimental constraints.

Findings

Lower bound on dark baryon mass: ~300 GeV

Excluded fermions with electroweak-breaking masses based on lattice data

Constraints from dark meson decay, collider limits, and direct detection

Abstract

We present a new model of "Stealth Dark Matter": a composite baryonic scalar of an $SU(N_D)$ strongly-coupled theory with even $N_D \geq 4$. All mass scales are technically natural, and dark matter stability is automatic without imposing an additional discrete or global symmetry. Constituent fermions transform in vector-like representations of the electroweak group that permit both electroweak-breaking and electroweak-preserving mass terms. This gives a tunable coupling of stealth dark matter to the Higgs boson independent of the dark matter mass itself. We specialize to $SU(4)$, and investigate the constraints on the model from dark meson decay, electroweak precision measurements, basic collider limits, and spin-independent direct detection scattering through Higgs exchange. We exploit our earlier lattice simulations that determined the composite spectrum as well as the effective Higgs coupling of stealth dark matter in order to place bounds from direct detection, excluding constituent fermions with dominantly electroweak-breaking masses. A lower bound on the dark baryon mass $m_B \gtrsim 300$ GeV is obtained from the indirect requirement that the lightest dark meson not be observable at LEP II. We briefly survey some intriguing properties of stealth dark matter that are worthy of future study, including: collider studies of dark meson production and decay; indirect detection signals from annihilation; relic abundance estimates for both symmetric and asymmetric mechanisms; and direct detection through electromagnetic polarizability, a detailed study of which will appear in a companion paper.