Mono-lepton Signature of a Neutrino-philic Dark Fermion at Hadron Colliders

Searching for dark matter at high-energy colliders and direct detection experiments can effectively cover nearly the entire mass range from the MeV to the TeV scale. In this paper, we focus on four-fermion contact interactions formulated within the framework of Effective Field Theory. Specifically, we present a detailed analysis of mono-lepton production at the LHC. Our results demonstrate that tensor operators exhibit superior sensitivity in the mono-lepton channel, constraining energy scales up to 3\,TeV for a nearly massless dark fermion using current LHC data. Moreover, these operators mediate both spin-independent and spin-dependent absorption processes in nuclear targets. A systematic comparison of constraints between direct detection experiments and collider measurements reveals the LHC's distinct advantage in exploring sub-GeV dark matter candidates while maintaining competitive sensitivity at the TeV scale. Notably, direct detection experiments such as Super-Kamiokande and Borexino achieve complementary constraints in the 10-100\,TeV mass range through their unique capabilities: utilization of light nuclei targets, large exposure volumes, and distinctive features of the recoil energy spectra.