2D Muon Scattering Tomography: POCA Reconstruction

This simulator is a genuinely two-dimensional counterpart to the 3D cosmic-ray muon scanner: everything happens in a single vertical x–y slice through the scan volume, with four real tracking planes (two above the hidden object, two below) instead of one static mid-plane bin. Each falling muon's two hits above fix a straight incoming line and its two hits below fix a straight outgoing line; where those lines cross — the 2D reduction of the point-of-closest-approach (POCA) algorithm real muon trackers use — is taken as the reconstructed scattering location. The size of each kink is still generated from real physics: the path length through the hidden material and its radiation length feed the Highland multiple-Coulomb-scattering formula, applied here as a random walk of many small sub-kicks whose summed variance is verified numerically to converge to the closed-form Highland result. Accumulating squared scattering angle at every reconstructed intersection point slowly reveals the size, position and density of whatever material is hidden inside.