Search for Light Dark Matter in Rare Meson Decays
Ze-Kun Liu, Ying Li, Biao-Feng Hou, Qin Chang
TL;DR
This work probes sub-GeV dark matter through rare meson decays mediated by a $Z^{\prime}$ portal. By mapping a UV $Z^{\prime}$-DM-quark interaction onto a dark low-energy EFT (DLEFT) and computing differential decay widths for $B\to P(V)\chi\bar{\chi}$ and $K\to \pi\chi\bar{\chi}$, it derives upper bounds on the couplings $g_f^{V,A}$ and $g_{\chi}^{V,A}$ from current data. The resulting constraints are translated into DM-nucleon cross sections for both spin-independent and spin-dependent interactions, revealing that rare meson decays provide competitive and background-free probes of sub-GeV DM, with sensitivity approaching or surpassing some direct-detection limits and offering strong complementarity to neutrino-floor-limited searches. The findings underscore the potential of flavor-changing neutral current processes as powerful tools for light DM model building and motivate future experimental and theoretical refinements to enhance sensitivity in the sub-GeV regime.
Abstract
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 $Z^{\prime}$ 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.