Extended exemple: gammatherapy

hello everyone, i am so glad to join this forum. i am a student and i am very new to Geant 4
so i am trying hard to understand it , in order to start making my own simulation.

now i have a little project about the exemple gammatherapy from the extended exemples, and i am asked to make a report (description ) about the different steps of this geant4 exemple. (as a beguinning )

i just started , and i am now at the phisiclist step and i have a little problem with it … i found the code in the folder /src and what i know about physiclist is that it contain the construct particuls , the construct process(for physics process) and the setcut

1/ So my first question is : where can i find the construct particul ? becaus there is no information about the used particules in this exemple within the file /src/physicList.cc

2/ what is the meaning of setcut ? and where can i find it in the code ?

thank you so much, and sorry if the questions are not that relevent … this is because i am very very new to Geant4

_Geant4 Version:_geant4-v11.1.0
_Operating System:_ubuntu 20.04