TeV-Scale Thermal WIMPs: Unitarity and its Consequences

Understand

We re-examine unitarity bounds on the annihilation cross section of thermal-WIMP dark matter.

• For high-mass pointlike dark matter, it is generic to form WIMP bound states, which, together with Sommerfeld enhancement, affects the relic abundance.
• We show that these effects lower the unitarity bound from 139 TeV to below 100 TeV for non-self-conjugate dark matter and from 195 TeV (the oft-quoted value of 340 TeV assumes $\Omega_{DM} h^2 = 1$) to 140 TeV for the self-conjugate case.
• For composite dark matter, for which the unitarity limit on the radius was thought to be mass-independent, we show that the largest allowed mass is 1 PeV.