Muography and Geology: Does It Matter Which Continent You Stand on?

Abstract

The present work has one aim and one aim only: to increase the geological credibility of simulations of muon propagation in real-world rocks. We accomplish this by introducing five different sets of real-world geological systems. Our approach contrasts with the so-called “standard rock” approach, which uses a simplified rock composition as a proxy for geological materials. However, while the conventional approach relies on an assumed average geological composition, it fails to appreciate the complexity of real-world rocks, which indeed are extremely varied in both density and chemical composition. In contrast, each of the five geological systems we have used in our simulations is statistical in nature and represent an average composition of a massive number of similar type of rocks from around the world. The studied real-world geological systems were (1) upper continental crust, (2) bulk continental crust, (3) lower continental crust, (4) oceanic crust, and (5) oceanic upper mantle. Furthermore, water and standard rock were used as references as those are more familiar materials among astroparticle physicists. The simulations were conducted using the standard tools of Geant4 (muon attenuation in materials) and CORSIKA (muon energy in intensity distributions on the ground level), while the parametrized estimates were based on the works of Guan et al. (modified from the Gaisser formula) and Chirkin and Rhode (MMC code). The muon rates
were compared to the experimental data of Enqvist et al. extracted in the Pyhasalmi mine, Finland.