Stability of "StableParticles" in STDHEP reader

[Sho IWAMOTO]

In DelphesSTDHEPReader::AnalyzeParticles, particle stability is determined with pdgParticle->Stable(), where pdgParticle = fPDG->GetParticle(pid);.

However, ROOT 5.34.21 has a strange behavior as follows:

root [0] db = TDatabasePDG::Instance();
root [1] db->GetParticle(24)->Stable()
(const Int_t)0
root [2] db->GetParticle(-24)->Stable()
(const Int_t)1

I don't know this is a bug of ROOT or a spec, and I know this fact does not affect usual analysis; so I just leave a comment here.

[Pavel Demin]

Thanks for finding this problem.

I agree that it should not affect usual analysis.

ROOT 6.00.02 shows the same results.

Have you notified the ROOT developers about this?

[Sho IWAMOTO]

I didn't, and I have just done. ​https://sft.its.cern.ch/jira/browse/ROOT-6889

This is actually because the database pdg_table.txt has no information other than names for antiparticles; it might be better to understand this as a spec... Anyway we should wait for ROOT developers' replies.