Muography with symmetric background subtraction

Radiographic analysis of the cosmic muon flux measured by the underground or surface detectors is usually based on the subtraction of the uninteresting background flux, obtained by the Monte Carlo simulation or by direct open-sky muon flux measurement. In this contribution, we promote a new method based on exploring the intrinsic acceptance symmetry of the muon detector and using the symmetric features of the object (or overburden) being studied. We show that discrete reflection or rotational symmetries of the muon detector (acceptance) may be utilized for directly obtaining the inhomogeneity maps of the objects studied, provided the overburden (background) or the geometry of objects being studied (e.g., pyramids) also exhibit internal symmetries. The method principle is demonstrated here using only a simple toy Monte Carlo muon flux example. Its application to real cosmic muon data was verified elsewhere. We suggest that the design (acceptance) of the muon detector and its location can be optimized in such a way that a simple data-based angular muon flux subtraction may directly reveal the presence of the explored object inhomogeneities.