Does a unique particleID number exist?

Hello, I am very new to Geant and I am trying to sum the scintillation energies of individual gamma particles for a given event. Right now we have the functionality to sum the scintillation energies for a given event, but not by particle. Is there a simple “particleID” or similar that could give a unique value for a given particle that we could use to accomplish this? Any other ideas would be greatly appreciated as well!!