Multi-Messenger and Paleo-Detector Probes of the LZ Dark Matter Signal

Abstract

The LUX-ZEPLIN collaboration recently reported a $2.6\sigma$ excess at a nuclear recoil energy of $248\ \text{keV}$, challenging the standard elastic WIMP paradigm. We show that a leptophobic inelastic dark matter model with a vector mediator naturally explains this anomaly while evading all low-energy direct detection constraints. The viable parameter space features $m_{\chi_1}>100~\text{GeV}$ and mass splitting $\delta\sim 200\text{--}300\ \text{keV}$. Our multi-messenger analysis reveals that neither the heavy ($10\ \text{GeV}$) nor light ($10\ \text{MeV}$) mediator scenario reproduces the Fermi-LAT Galactic center excess, and neutrino fluxes remain consistent with IceCube limits. Both scenarios predict recoil tracks near 80 nm in lead-bearing paleo-detectors. At an optimistic uranium-238 concentration of \(10^{-12}\) g/g, 10 mg Gyr of exposure could yield an excess above the estimated background even when astrophysical signals are negligible. The LZ anomaly, if confirmed, points toward a dark sector with inelastic transitions and leptophobic couplings, with the paleo-detector providing the smoking-gun evidence.