Probing Cosmic Ray Composition and Muonphilic Dark Matter via Muon Tomography

This Letter presents a novel cosmic-ray scattering experiment employing a resistive plate chamber muon tomography system. By introducing the scattering angle between incident and outgoing cosmic-ray tracks as a key observable, this approach enables simultaneous studies of secondary cosmic-ray composition and searching for new physics. During a 63-day campaign, 1.18 million cosmic ray scattering events were recorded and analyzed. By performing combined template fits to the observed angular distribution, particle abundances are measured-for example, resolving the electron component at ∼2% precision. Furthermore, constraints are established on elastic muon-dark matter (DM) scattering cross sections for muonphilic dark matter. At the 95% confidence level, the limit reaches 1.61×10^{-17} cm^{2} for 1 GeV slow DM, demonstrating the sensitivity limit to light muon-coupled slow DM, in scenarios where a strongly interacting dark matter component is captured and thermalized within Earth, leading to large surface densities.