A New Direction in Dark-Matter Complementarity: Dark-Matter Decay as a Complementary Probe of Multi-Component Dark Sectors

Understand

In single-component theories of dark matter, the $2\to 2$ amplitudes for dark-matter production, annihilation, and scattering can be related to each other through various crossing symmetries.

• These crossing relations lie at the heart of the celebrated complementarity which underpins different existing dark-matter search techniques and strategies.
• In multi-component theories of dark matter, by contrast, there can be many different dark-matter components with differing masses.
• This then opens up a new, "diagonal" direction for dark-matter complementarity: the possibility of dark-matter decay from heavier to lighter dark-matter components.