Correct the rotation of the event according to the beam direction. Refs #3625 (!2127) · Merge requests · Computing / cbmroot

Volker Friese requested to merge v.friese/cbmroot:beam_rot into master Jun 25, 2025

See discussion in #3625.

The rotation of the event following the beam direction is not properly implemented in FairRoot (FairPrimaryGenerator::AddTrack). To cope with this, the method AddTrack is re-implemented in CbmPrimaryGenerator, which derives from FairEventGenerator. The changed implementation (using TVector3::Rotate() instead of TVector3::RotateUz()) follows the proposal by O. Lubynets in https://github.com/lubynets/FairRoot/commit/ef9115f456859c6d920272b7c0a5c8f46b4a054d.

See also the respective discussion in the ROOT forum.

It may be worthwile to consider porting the change to FairRoot.

Correct the rotation of the event according to the beam direction. Refs #3625

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