Search for light dark matter in rare meson decays

Current dark matter direct detection experiments have low sensitivity to sub-GeV dark matter. In this work, we demonstrate that rare B and K meson decays with missing energy in the final state can serve as efficient probes in this mass range. We analyze a generic Z ′ portal dark matter model and derive upper limits on its parameters from experimental bounds on the rare B and K meson decays. Our results show that such meson decay processes provide complementary constraints to current direct detection experiments for sub-GeV dark matter, particularly for interaction forms mediated by dark matter momentum-dependent operators.