DD4hep Meeting January 15th, 2026

Present:     Andre, Juan, Markus, Peter, Thomas

Apologies: 

Link to minutes of previous meeting

Merged PRs

• PR1540:        Fix HepMC3 reading GenRunInfo using root reader (Simon Gardner)
• PR1541:        Fix example BoxOfStraws_DDSim (Markus)
  +ISSUE1520     Missing segmentation in the box of straws (Juan)
• PR1542:        Calling DD4hep plugins from DDG4 python and G4 prompt (Markus)
• PR1545:        Use and cache ROOT_LIBRARY_PATH environment variable for plugins (Andre)
• PR1547:        fix: install into free-threaded python3.14t/site-packages prefixes (Wouter)
• PR1550:        CMake cache variables for plugin-related commands (Seth R. Johnson)
  +ISSUE1546:    Plugin load fails depending on pythonpath name

Closed PRs, closed issues and fixed problems

• ISSUE1537: G4Kernel configuration error (gondiaz)
• ISSUE1549:  cmake not picking up boost from /cvmfs/k4hep (Daniel Jeans)

Pending Problems

• ISSUE1297:  Possible to dump all available readout elements?
                        ==> Possibly a copy of unsolved ISSUE580 from Valentin about enumerating all sensitive cells.
• ISSUE1320:  Replacing a Handle<Segmentation> which contains a MultiSegmentation with the underlying Segmentation
                        ==> Unclear what he really means.
• ISSUE1335:   Uniform random picking of points on detector surfaces for noise studies
                         This problem is linked to #1297 and #580.
• ISSUE1443:  Make user particle handler extensible
                         ---> Maybe we should take advantage and re-collect requirements.
• ISSUE1458: XML file vs TGeoStored geometry in GenFit
• ISSUE1487: The test t_DDDigi_sim_test_weighted_deposit_overlay can fail (Juan)
    ---> Unstable test 
• ISSUE1492:  Readout segmentation for multiple cylinders with offset axes question
                        ----> Unclear code in CylindricalGridPhiZ.cpp line 80
                        ----> Try special case where axis is identical to beam axis.
• ISSUE1501: Bug/Feature: Condense duplicated particle contributions in calorimeter question
• ISSUE1514: How to convert Geant4TrackID into MCParticle Parent ID
• ISSUE1515: How to apply the step_length_max limit to neutral particles?
                        ----> Issue opened by Andreas Loeschke
• ISSUE1535: How to add new output variables in Hitsquestion (matclim -> DD4SHip)

New:

• ISSUE1543:     (yet another) question about simulating particle lifetime in ddsim (Daniel Jeans)
• ISSUE1544:     Feature: additional DetTypes for backward and far detectors (Derek M Anderson)

Pending PR:

• PR1240:        Add multithreading support to ddsim
• PR1314:        Cylinder segment surface (Armin Ilg)
• PR1503:        [WIP] Add flag for fast simulation to MCParticle (Thomas)
• PR1548:        Geant4InputHandling: Only set the propertime of a particle if it is l… (Andre)
• PR1551:        [WIP] Fix to global alignment for simulation of misaligned geometries (Markus)

Round Table

Juan:.     NTR
Markus:  NTR
Peter:      NTR
Andre:     NTR
Thomas: NTR

AOB

Next meeting:   February 5th, 2026