Hi Guillaume. Thank you very much for this fix, it seems perfect to me. I should have realised also this initialisation was not done...

what's the impact of this?

Is there a reason to use TRandom3 at all? As far as I can see the only place in the entire WCSim that it is used is here, which could be changed to use the G4 random generator to match the random number generation used anywhere else.

Hi,

what's the impact of this?

-> impact should be negligible for 99% of WCSim usage. Normally, G4 randomizer should be used in WCSim. However, for the Rn generator, since we are using TF2 Random functions, it's absolutely necessary.

Is there a reason to use TRandom3 at all?

-> gRandom is TRandom3 by default, but the header doesn't really matter I guess.

As far as I can see the only place in the entire WCSim that it is used is here, which could be changed to use the G4 random generator to match the random number generation used anywhere else.

-> No, this is not the same, gRandom is the default ROOT Randomizer, but here ranGen is declared as another Randomizer. Actually, I think ranGen initialization is quite bad: it is always initialized with the default seed so it will always produce the same sequence. I think you are right that replacing ranGen by the default G4 random generator would be better.

Ah I see, I had searched for any occurrence of TRandom and that was all I could find. I didn't realise that the Rn generator used TRandom in a "hidden" way through the TF2 random functions. Thanks for the clarification.