http://arxiv.org/abs/2301.04513
Pions of a dark sector gauge group can be strongly interacting massive particle (SIMP) dark matter, produced by the freeze-out of $3 \to 2$ interactions, with naturally large self-interactions. We study if adding a dark photon to the set-up can do it all: i) maintain thermalization with the visible sector, ii) resonantly enhance the $3\to2$ interactions, thus allowing for a perturbative pion description, and iii) provide a velocity dependent self-interaction that can affect small scale structure formation. We find that this is marginally excluded, as the required kinetic mixing is too small to maintain thermal equilibrium with the SM. Dropping the small scale structure requirement iii), a viable setup is reproduced for dark charges of $\alpha_d = 0.01-1$ and a dark pion mass $m_\pi \geq 30$ MeV. Late time annihilations are non-negligible making the SIMP dark pion a bit WIMPy.
P. Braat and M. Postma
Thu, 12 Jan 23
12/68
Comments: 17 pages, 14 pages appendices, 3 figures