Campaign 2026-04

Unlike the other campaigns, this one is not a full production run. It is a focused investigation into two Lambda-related MCParticle bugs affecting the ePIC + DD4hep simulation chain.

Bugs under investigation

1. MCParticle endpoints / daughter tree wrong for Lambdas
   eic/epic#1069

2. Tracking-volume G4 handler drops Lambda decay info
   eic/epic#1081 (review)

The symptom in both cases is the same: primary Lambdas in the output MC record either have no daughters, have wrong endpoint coordinates, or are replaced by a shower-like daughter list — which breaks any downstream analysis that follows the Λ -> p π- or Λ -> n π0 decay chain.

Variants produced

Only DD4hep + afterburner were re-run; no full reconstruction. The runs differ only in how the Geant4 tracking-volume handler and the --part.userParticleHandler="" flag are configured:

Folder tag	What was changed
dd4hep_saveall	Save all particles
dd4hep_26-03	Old (bugged) behavior
dd4hep	Updated (fixed), longer tracking volume from the issue above

Directories ana, csv_dd4hep, csv_reco, reco correspond to results from dd4hep, i.e. new fixed tracking volume data.

Data location (ifarm)

/work/eic/users/romanov/meson-structure-2026-04-check/

Reports

• Tracking volume (saveall variant)