Hello, I'm attempting to model neutron-antineutron annihilation inside an 40Ar nucleus. As a first step I'd like to just create a pi^+ and pi^- back-to-back somewhere inside the 40Ar nucleus and record what gets out. First question, is this the right MC-code for this application? Second, I've attempted to modify the stdapp/gEvGenHadronNucleus.cxx code to accomplish this task, but doesn't look like I'm able to start the pions inside the nucleus. Any suggestions? Thanks,