- May 5, 2022, 2:30 pm US/Central
- Jan Heisig, Louvain University
Bound-state formation effects can have a large impact on the
dynamics of dark matter freeze-out in the early Universe, in particular,
for colored coannihilators. We present a general formalism to include an
arbitrary number of excitations of bound states in terms of an effective
annihilation cross section. For a coannihilator in the fundamental
representation of SU(3)c, we discuss radiative bound-state formation,
decay, and electromagnetic transition rates among them. We then assess
the impact of bound states within a minimal dark sector containing a
Majorana dark matter candidate and a colored scalar t-channel mediator.
We consider the well-known coannihilation regime as well as the regime
of conversion-driven freeze-out (or coscattering), where the relic
abundance is set by the freeze-out of conversion processes. We find that
the latter is considerably enhanced into the multi-TeV region due to
bound-state effects. This has far-reaching implications for the search
strategies at the upcoming LHC runs as conversion-driven freeze-out
predicts a long-lived coannihilator.