Large N-ightmare dark matter

Abstract

A dark QCD sector is a relatively minimal extension of the Standard Model (SM) that admits Dark Matter (DM) candidates, but requires no portal to the visible sector beyond gravitational interactions:a “nightmare scenario” for DM detection.We consider a secluded dark sector containing a single flavor of light, vector-like dark quark gauged under (N).In the large-N limit, this single-flavor theory becomes highly predictive, generating two DM candidates whose masses and dynamics are described by few parameters:a light quark-antiquark bound state, the dark analog of the η' meson, and a heavy bound state of N quarks, the dark analog of the Δ++ baryon.We show that the latter may freeze-in with an abundance independent of the confinement scale,forming DM-like relics for N ≲ 10, while the former may generate DM via cannibalization and freeze-out.We study the interplay of this two-component DM system,and determine the characteristic ranges of the confinement scale,dark-visible sector temperature ratio, and N that admit non-excluded DM,once effects of self-interaction constraints and bounds on effective degrees of freedom at the BBN and CMB epochs are included.