Abstract
We consider a light dark matter candidate that is produced by the freeze-out mechanism with $3\ensuremath{\rightarrow}2$ annihilations, the so-called strongly interacting massive particles (SIMPs). SIMPs are identified as dark pions in dark chiral perturbation theory (ChPT) in which both light mass and strong coupling needed for SIMPs can be realized by strong dynamics. In QCD-like theories with $SU(3{)}_{L}\ifmmode\times\else\texttimes\fi{}SU(3{)}_{R}/SU(3{)}_{V}$ flavor symmetry, including dark vector mesons in the hidden local symmetry scheme, we illustrate that dark vector mesons unitarize the dark ChPT efficiently, thus determining the correct relic density condition within the validity of the dark ChPT.
Highlights
The weakly interacting massive particles (WIMPs) have been regarded as a consistent paradigm for dark matter (DM), accommodating the large-scale structure of the Universe, the gravitational lensing and the cosmic microwave background anisotropies, etc
Deviations from the WIMP paradigm, such as the too-big-to-fail [1,2,3,4] and core-cusp problems [5], have been observed at galaxy scales, rendering the DM profile from the center of the Galaxy being cored unlike the expectation of the N-body simulations with WIMPs
We introduce a consistent model for strongly interacting massive particles (SIMPs) in the dark chiral perturbation theory (ChPT) with QCD-like chiral symmetry, SUð3ÞL × SUð3ÞR=SUð3ÞV
Summary
The weakly interacting massive particles (WIMPs) have been regarded as a consistent paradigm for dark matter (DM), accommodating the large-scale structure of the Universe, the gravitational lensing and the cosmic microwave background anisotropies, etc. New freeze-out mechanisms for the thermal production of light dark matter with sub-GeV-scale mass have been proposed in the literature such as 3 → 2 channels [12,13], forbidden channels [14], codecay channels [15], and inelastic scattering channels [16]. Near the validity region of ChPT (mπ=fπ; jp⃗ πj=fπ ∼ 2π), there will appear new resonances (as in ordinary hadron physics) that have to be included in the chiral Lagrangian explicitly. We regard dark pions as SIMPs and improve the dark ChPT by including vector mesons explicitly as gauge bosons associated with hidden local chiral symmetry.
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