GeV-Scale Composite Dark Matter: Inelastic Shielding and Secluded Freeze-out

Null results from multi-ton direct-detection experiments challenge the standard WIMP paradigm, motivating dark-sector scenarios where low-momentum scattering is naturally suppressed. We develop a minimal effective field theory framework for GeV-scale composite dark matter featuring two nearly degenerate fermionic states, χ1 and χ2, stabilized by an exact dark parity. The composite nature is encoded through momentum-dependent effective interactions, parameterized by a form factor F (q2). Our principal contribution is the identification of a robust sub-GeV window where the observed relic density (Ωh^2 ≃ 0.12) is reproduced via secluded thermal freeze-out, while direct detection signals are extinguished by inelastic kinematic shielding. Crucially, we demonstrate that for mχ ≃ 0.75 GeVand ∆ ∼ 6.6 MeV, the effective interaction scale can remain as low as ΛSM ∼ 730 GeVwithout violating bounds from CRESST-III or SENSEI. Complementary regimes realizing infrared or UV-dominated freeze-in are also delineated. We provide a complete cosmological pipeline and benchmark scenarios, highlighting that the decisive protection mechanism is kinematic rather than amplitude suppression, with compositeness providing additional motivation for the near-degenerate spectrum.