Dark Matter from Baryon Asymmetry

TL;DR

The paper addresses why the cosmic densities of dark matter and baryons are of the same order by proposing a shared origin in which dark matter $S$ arises non-thermally from the decay of a messenger $X$ that carries $B-L$ and links to the baryon asymmetry. It develops a minimal model with only $S$ (a gauge-singlet fermion) and $X$ (a TeV-scale colored, long-lived particle) and analyzes how $X$-driven processes couple the two sectors, including a concrete realization with $X$ and $S$ interacting via a dimension-six decay operator. The authors derive predictions for the dark-matter mass (e.g., $m_{ m DM}/m_p\approx4.1$ in their explicit model, yielding $m_{ m DM}\approx3.9$ GeV) and explore cosmological bounds on the decay scale and messenger mass, as well as collider signatures reminiscent of long-lived gluinos. The work provides a testable framework with distinctive LHC phenomenology, where $X$ would appear as a TeV-scale, long-lived colored state forming $T$-hadrons and potentially giving bound-state signals, thereby offering a route to probe the baryon-dark-matter connection experimentally.

Abstract

The measured densities of dark and baryonic matter are surprisingly close to each other, even though the baryon asymmetry and the dark matter are usually explained by unrelated mechanisms. We consider a scenario where the dark matter S is produced non-thermally from the decay of a messenger particle X, which carries the baryon number and compensates for the baryon asymmetry in the Universe, thereby establishing a connection between the baryonic and dark matter densities. We propose a simple model to realize this scenario, adding only a light singlet fermion S and a colored particle X which has a mass in the O(TeV) range and a lifetime to appear long-lived in collider detector. Therefore in hadron colliders the signal is similar to that of a stable or long-lived gluino in supersymmetric models.