New Constraints on Cosmic-ray boosted Sub-GeV Dark Matter via Light Mediators

TL;DR

This paper explores how cosmic-ray upscattering can enable underground detectors to detect sub-GeV dark matter with light mediators, extending sensitivity beyond traditional methods.

Contribution

It introduces a novel analysis of cosmic-ray boosted dark matter detection considering four interaction models and derives new constraints on light mediators from multiple experiments.

Findings

Constraints vary with mediator mass, showing a turnover around 10^{-2}--10^{-3} GeV.

Extends direct detection sensitivity into the sub-GeV dark matter mass range.

Highlights the importance of momentum dependence in light-mediator interactions.

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 $10^{-6}$ 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 $10^{-2}$--$10^{-3}~\mathrm{GeV}$. 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.