/*! @page  pga The Primary Generator Action

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 * The initial parameters of the particle(s) to simulate are given in the 
 * LEMuSRPrimaryGeneratorAction class. This mandatory class work in interplay
 * with the LEMuSRParticleGun to create each new event of the simulation.
 * 
 * An event is the track of one particle and all the particles created during its
 * evolution in the detector, by decay, scattering or any other kind of process.
 

*/