Millimeter-Resolution Cosmic-Ray Imaging via Projection-Shifted Muon Transmission Tomography

Cosmic-ray muon imaging provides a non-destructive inspection technique, yet achieving millimeter-resolution imaging within practical timeframes remains challenging. Here we introduce Projection-shifted MUon transMission tomogrAghy (P$\mu$MA), a hybrid framework that seamlessly integrates transmission and scattering information to enable high-resolution imaging. Unlike conventional approaches that rely on scattering-angle measurements to locate scattering points, P$\mu$MA constructs transmission tracks by connecting hit positions in upstream and downstream detectors. The material-induced angular deflection is then projected as a detectable shift in an imaging plane. This approach allows millimeter-resolution cosmic-ray imaging with as few as two detectors, significantly increasing acceptance and usable muon events, and substantially lowering detector and electronics costs. We also present multi-detector variants that incorporate scattering-angle selection to enhance contrast. Simulations of a 30 mm thick lead block demonstrate a knife-edge width of 1.196 mm. Experiments resolve 2 mm copper sheets within 2 days, surpassing conventional methods under matched conditions.