Hi @marmolRBG regarding of your question, I’m not a Geant4 expert…so let reply by an expert
Thank you @mkelsey yes, I want just to store data in ROOT Ntuples, so that I can use ROOT to analyse them. Unfortunately, yesterday while I was writing the ROOT macro to read the hit coordinates stored in the Ntuples, I noticed i.e. my second target is positioned at (0,0,2.3 cm) and it has a 0.3 cm thickness (so its range along the z-axiz should be [2.3cm-2.6cm], but looking for hits position in that target, I get some hits in the range 22cm-25cm. I discussed about my problem in this topic Position problem in targets Do you know what is the problem?