Opened 7 years ago
#1170 new Bug
GenParticle mass not converted to GeV when HEPMC file is encoded in MeV
| Reported by: | Andrew Chisholm | Owned by: | |
|---|---|---|---|
| Priority: | minor | Milestone: | |
| Component: | Delphes code | Version: | Delphes 3 |
| Keywords: | GenParticle Unit MeV GeV Mass | Cc: |
Description
Dear Delphes Team,
First of all, let me thank you for developing and continually maintaining Delphes, I think it is in incredibly useful tool for the HEP community!
I noticed that when I read a HEPMC file in which the 4-vectors are encoded in MeV, while the momentum components (and energy) in the GenParticle collection are converted to GeV, the particle mass (Particle.Mass) is not and remains in MeV.
I browsed through the source code and notice in "DelphesHepMCReader.cc" that in the case the HEPMC file is identified as being encoded in MeV, no correction is applied to the particle mass. Perhaps at this line:
https://cp3.irmp.ucl.ac.be/projects/delphes/browser/git/classes/DelphesHepMCReader.cc#L353
one should also multiply the mass by "fMomentumCoefficient" as is done for the momenta?
I'm not sure if this behaviour is intended, but I at least found this mis-match between the mass and momentum units very confusing until I identified the source of the problem.
To avoid potential problems for users who read in an MeV encoded HEPMC file, perhaps this behaviour should be addressed?
Thanks a lot,
Andy
