I’d like to simulate charge exchange of p- (Proton + two electrons)
Shoot the 5 MeV p- to the thin carbon plate ( few mm thickness)
Then some of p- loss electrons to be p+ or H (hydrogen).
So I want get the ratios of p+, H, o-.
Which physics list is suitable for that interaction?
That’s an almost pure EM physics process, C + H- → C + p + 2e, or C + H + e. There may also be proton capture reactions (12C + p → 13N + gamma), although that may be suppressed for the negative ion beam (I’m not familiar enough with these low energies to be certain).
I would expect that FTFP_BERT possibly with one of the EM options, should be sufficient for your purposes. If you are using G4ParticleGun as your source, you’ll configure your H- beam as