Strong CMB Constraint On P-Wave Annihilating Dark Matter

Understand

We consider a dark sector consisting of dark matter that is a Dirac fermion and a scalar mediator.

• This model has been extensively studied in the past.
• If the scalar couples to the dark matter in a parity conserving manner then dark matter annihilation to two mediators is dominated by the P-wave channel and hence is suppressed at very low momentum.
• The indirect detection constraint from the anisotropy of the Cosmic Microwave Background is usually thought to be absent in the model because of this suppression.