New constraints on cosmic-ray boosted sub-Gev dark matter via light mediators

Abstract Traditional direct detection experiments lack the sensitivity to probe the sub-GeV dark matter(DM), primarily due to the low energy of the expected nuclear recoils. In this work, we investigate cosmic-ray (CR) upscattering as a mechanism to accelerate DM particles to detectable velocities in underground experiments. By analyzing four models of DM-nucleon interactions – namely scalar, vector, pseudoscalar, and axial-vector mediators – we derive constraints on the coupling parameters using data from the LZ, XENON, and Borexino experiments, covering mediator mass from $$10^{-6}$$ 10 - 6 to 1 GeV. As the mediator mass varies, the shift in dominance between momentum transfer and mediator mass leads to a turnover in the constraints around $$10^{-2}$$ 10 - 2 – $$10^{-3}~\textrm{GeV}$$ 10 - 3 GeV . Our results extend the reach of direct detection into the sub-GeV window and clarify the critical role of momentum dependence in light-mediator scenarios.