Present: Boris, Domenico, Mateusz, Michele, Youri
V0 Finders
On-the-fly (aka online),
Uses clusters for energy loss correction. By default, energy loss correction on tracks assumes that they are crossing all the layers. Only after you know the position of the V0, you can compute the correct energy loss. Currently used for gamma conversion as the main V0 finder (Boris), even if both are used in the conversion paper.
Offline
Online was used to tune offline. Combines offline tracks. Online is really better only at low pt (below 500-600 MeV lambda). That's why they agree well at high pt.
Offline could be moved to AODs or post reco, if needed. In the future, the energy loss calculation will also be improved for the offline.
Systematics due to cut variations are difficult to study with the on the fly, because cuts are interleaved with the reconstruction. Systematics are easier with the offline, so if the 2 agree offline is better for the systematic studies.
Cascade reconstruction only uses the offline
Peter said before the meeting:
"My opinion is that we had very good reasons to consider the V0s and cascades as part of the reconstruction:
- V0s and cascades are well defined objects
- possibility to run both on-the-fly and offline vertexers
- the relatively heavy processing (especially in case of PbPb)"
Library
V0 code is now in ESD. Move it back to STEER for the future (offline reco)? If it is on STEER, you cannot use it in the filter or at analysis. If it is in the ESD, accessing OADB and geometry is more tricky.
Conclusions:
- Online will stay at reconstruction, until the energy loss correction is properly implemented for the offline
- Implementing Eloss on the offline is a long-term goal due to technical difficulties (need to access OCDB and geometry, will take some time to validate)
- The offline and cascade finder should stay at reconstruction, because the processing is heavy
- The V0 code will stay in ESD. Even if we don't foresee changes in the cuts again (we already have them tuned for PbPb and pp), we prefer to keep the flexibility
- We'll meet again in 6 months, we'll also need Marian.