When we are running reference particles we do not want the particle to scatter
nor have fluctuations in the energy loss. In order to accomplish this we call
G4VEnergyLossProces::SetLossFluctuations. The problem is that if you remove all
fluctuations you do not get any energy loss at all. For muons at around 200
MeV/c, it seemed safest to keep the fluctuations for bremsstrahlung, and remove
them from more dominating processes.

  std::string process[3] = {"msc", "muIoni", "muPairProd"};
  std::string muon[2]     = {"mu+", "mu-"};
  G4ProcessTable * procTable = G4ProcessTable::GetProcessTable();
  ...
        ((G4VEnergyLossProcess*)procTable->FindProcess(process[j],
muon[i]))->SetLossFluctuations(isActive);
  ...