Thank you very much Daniele for your very detailed answer, it was really helpful.
Sorry if I didn’t specify it well in my initial question, but what I was trying to do was to know the production vertex of the particles I was interested in (like muons) and the process that produced them. But what you have explained me should be sufficient for my purpose. Thanks again.
I’ll try what you wrote right away, and I’ll let you know.
EDIT: Tried the code and it works fine!
Antonino