VMC meeting

40/R-D10 (CERN)



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Andrei Gheata (CERN)
This meeting will follow-up open issues related to the Virtual Monte Carlo framework.

GEANE - related issues

  • Presentation by Andrey Lebedev who described the procedures used in CBM for track reconstruction, including comparisons with GEANE. Andrey expressed the concerns about future maintenance of GEANE and difficulties in including new developments in the FORTRAN code. Their track propagation approach as C++ alternative to GEANE looks promissing.
Mohammad pointed out that some effort will be needed for re-writing EUSTEP subroutine in a manner close to TGeant3::Gustep() so that users would have more control on GEANE stepping.
Action item 1: Try to figure out the timeline/responsible for re-writing EUSTEP and possibly come-up with more development requirements (Mohammad). Would be good to notify also Andrea Fontana for the next meeting.
  • Presentation by  Alessandra Filippi about a feature of the GEANE release at low energies that generate un-physical peaks in the reconstructed momentum spectra. Their patch for ERTRCH function that replaces the step-function energy correction seems to remove the un-wanted peaks.
Action item 2: Notify M.Maire about the issue so that it can be replaced in the GEANE release. (Rene)


Assemblies generate an additional geometry level in TGeo compared to GEANT4. It is unlikely that this will change soon in GEANT4, so the only way of getting the same behavior is what Ivana proposes: "user can build his volume tree path himself with not putting the assemblies in the tree. (I have somewhere this function, as we used something like this in MUON.)". Anyway, having an assembly volume as current volume during tracking should never happen.

Action item 3: See if Ivana's proposal/function is satisfactory (Ivana/Mohammad). Send me a simple example so I can reproduce the problem of assemblies appearing during tracking (Mohammad).

Disabling default GEANT3 particles and decay modes.

Mohammad claims that these may clash with other settings so he asks for this possibility.

Action item 4: Implement the possibility to configure not having G3 defaults so the user can use DefineParticle()/SetDecayMode() for defining his own. May consider the possibility to re-define decay modes for already registered particles. (Ivana/Andrei)

Cerenkov total reflection.

G4root interface not doing total reflection correctly.

Action item 5: Send me a simple macro to reproduce it (Mohammad). Fix it (Andrei).

Tracking location wrong in g4root.

A particle may end-up outside the setup giving the error message: "No physical volume found at track vertex: (107635,-190901,-638802)"
Action item 6: Fix this (Andrei)

"Proposed step is 0" issue in FLUKA-VMC

Observed in IlcRoot by Vito, reproduced by me, cannot track down the problem: There is no way (unless a lot of luck in spotting some dumb setting) of tracking this down symptomatically without tracing the program - not only the interface, but also FLUKA execution. We do not have FLUKA source code...

Action item 7: Try more ? (who?)
There are minutes attached to this event. Show them.
    • 10:30 10:35
      Introduction 5m
      A short introduction of the series of meetings
      Speaker: A.Gheata
    • 10:35 11:05
      Using GEANE in CBM track reconstruction algorithms 30m
      I'm working on the track reconstruction in the CBM experiment. And also I have put some efforts to the track propagation development, and compare the results with GEANE which we can use in cbmroot within the C++ interface. So, Denis suggested me to make a presentation about my developments for the track propagation algorithm/software.
      Speaker: Andrey Lebedev
    • 11:05 13:00
      General discussion 1h 55m
      1. GEANE issues: "We would like to bring to your attention a problem we think to have detected in the GEANE behaviour at low energies." from Alessandra Filippi/INFN 2. Assemblies: In Geant4 they have no Id but in ROOT they have, this has consequences to the geometry tree, i.e: If one try to relay on the mother-daughter relation the code will differ between the different navigations (ROOT and G4Native) is it possible to have a unified concept? Why do they have an Id in ROOT? Sometimes they are even seen in the simulation, something which should never happened. 3. In TGeant3.cxx there is many particles and decay modes that are hard coded there! If one try to define his own particles and decay modes it could conflict, and I already runs into problems and get very strange results before finding out that some things are hard coded. 4. Cerenkov total reflection: it is not working properly with GeoManager, when comparing with G4Native, it is working as expected (the same geometry is converted to Native G4 via VGM) 5. Geane-VMC: Eustep.F has to be re-written in C++ to have more control on the stepping behavior of Geane 6. "Proposed step is 0" issue in FLUKA VMC - In some condition there are some slow electrons (P ~= 500 KeV) that try to do very short step (~ 1.e-20 cm) so simulation code cannot go on. - reported by Vito in the context of ILCroot 7.The warning from Geant4 VMC when running with G4Root: "No physical volume found at track vertex: (107635,-190901,-638802)"
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