There are small differences in both ionization energy loss and catastrophic energy loss between positive and negative muons, which are usually neglected in most Monte Carlo simulations. These small differences can be amplified when measuring the charge ratio underground, where the total energy loss between the surface and the measurement is significant. Calculations of these effects for the case of MINOS will be shown.

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 5 (HE part 2), pages 1229-1232