Concerning the opening angle stuff, we will ignore it entirely, as the full selection strategy in fact. This requires a post on its own as special methods are in order to extract cutflows and things like that. For the moment, we solely focus on object definitions.

Am I right to think that the pTgamma value is to be retrieved from:
photon.momentum().Gamma() ?

This is just an abbrevation for the pt of the photon. The symbol of the photon is the Greek letter gamma. Therefore, one needs to use myphoton->pt()

Do we need to care about the hadronic fractionfh?

No. We can't do that with our simulation setup (that approximates the real experimental apparatus).