Scintillation yield by particle type

[jmunozv]

Nowadays the scintillation yield is set by parameter in all our detectors. Although it is a fix number for electrons, in the discussion about NextFlex MR we realized that sometimes that parameter is changed and set to a different value when running special alpha simulations, in which the scintillation yield is modified to accomplish with the quenching factor of heavy particles.

The point is that those simulations in which light and heavy particles play a role (cosmogenic studies, for instance), the scintillation yield considered in our simulations for all of them is the same, being wrong.

I propose to change the scintillation yield from a fix value set by parameter, by a hard-coded "particle-type" basis value.

[paolafer]

Starting from Geant4.10.7, it is possible to specify different scintillation yields, for different particles. However we need to know the scintillation yield of xenon for the following particles: proton, deuterium, tritium, alpha, neutron and electron. If we don't specify one of them, in the case the particle is produced, an error will be issued.