Reshuffled SIMP Dark Matter
  In this letter, we reanalyze the multi-component strongly interacting massive
particle (mSIMP) scenario using an effective operator approach. As in the
single-component SIMP case, the total relic abundance of mSIMP dark matter (DM)
is determined by the coupling strengths of $3 \to 2$ processes achieved by a
five-point effective operator. Intriguingly, we find that there is an
unavoidable $2 \to 2$ process induced by the corresponding five-point
interaction in the dark sector, which would reshuffle the mass densities of
SIMP DM after the chemical freeze-out. We dub this DM scenario as reshuffled
SIMP (rSIMP). Given this observation, we then numerically solve the coupled
Boltzmann equations including the $3 \to 2$ and $2 \to 2$ processes to get the
correct yields of rSIMP DM. It turns out that the masses of rSIMP DM must be
nearly degenerate for them to contribute sizable abundances. On the other hand,
we also introduce effective operators to bridge the dark sector and visible
sector via a vector portal coupling. Since the signal strength of detecting DM
is proportional to the individual densities, thereby, obtaining the right
amount of DM particles is crucial in the rSIMP scenario. The cosmological and
theoretical constraints for rSIMP models are discussed as well.
