Successful Freeze-Out of Strongly Interacting Dark Matter with Even-Numbered Interactions

Abstract

Strongly interacting massive particles π have been advocated as prominent dark matter candidates when they regulate their relic abundance through odd-numbered 3π→2π annihilation. We show that successful freeze-out may also be achieved through interactions XX→ππ once bound states X among the particles of the low-energy spectrum exist. In addition, X-formation hosts the potential of also odd-numbered 3π→2π annihilation processes, turning them into effective two-body processes πX→ππ. Bound states are often a natural consequence of strongly interacting theories. We calculate the dark matter freeze-out and comment on the cosmic viability and possible extensions. Candidate theories can encompass confining sectors without a mass gap, glueball dark matter, or ϕ3 and ϕ4 theories with strong Yukawa or self-interactions. Published by the American Physical Society 2024