Adapting the parameters of the physical processes

As stated before, the simulation of e.m. has been switched off. Moreover, in this problem we are interested only to the energy loss of the muons. For this purpose we do not need to follow all the secondary particles produced in muon interactions, but at the same time we are interested in a high level of accuracy, and this can be achieved only when the explicit production of secondaries is activated. This is the reason why we swith off the transport of $e^\pm$, all charged and neutral hadrons and, as usual, of neutrinos, by meand of the DISCARD directive. In this way we minimize the impact in terms of computing power.