Speaker
Description
The forbidden dark matter cannot annihilate into a pair of heavier partners, either SM particles
or its partners in the dark sector, at the late stage of cosmological evolution by definition. We point
out the possibility of reactivating the forbidden annihilation channel around supermassive black
holes. Being attracted towards a black hole, the forbidden dark matter is significantly accelerated
to overcome the annihilation threshold. The subsequent decay of the annihilation products to photon
leaves a unique signal around the black hole, which can serve as a smoking gun for the forbidden
dark matter. For illustration, the Fermi-LAT data around Sgr A∗ provides a preliminary constraint
on the thermally averaged cross section of the reactivated forbidden annihilation that is consistent
with the DM relic density requirement.
