GUTzilla Dark Matter
  Motivated by gauge coupling unification and dark matter, we present an
extension to the Standard Model where both are achieved by adding an extra new
matter multiplet. Such considerations lead to a Grand Unified Theory with very
heavy WIMPzilla dark matter, which has mass greater than ~10^7 GeV and must be
produced before reheating ends. Naturally, we refer to this scenario as
GUTzilla dark matter. Here we present a minimal GUTzilla model, adding a
vector-like quark multiplet to the Standard Model. Proton decay constraints
require the new multiplet to be both color and electroweak charged, which
prompts us to include a new confining SU(3) gauge group that binds the
multiplet into a neutral composite dark matter candidate. Current direct
detection constraints are evaded due to the large dark matter mass; meanwhile,
next-generation direct detection and proton decay experiments will probe much
of the parameter space. The relic abundance is strongly dependent on the
dynamics of the hidden confining sector, and we show that dark matter
production during the epoch of reheating can give the right abundance.
