Rerun s21 over s20 MC

[acontu]

S21 is a special case since the calo reconstruction was rerun so that it differs from the standard Reco14 used in S20. To be consistent with data, the following options should be appended:
https://svnweb.cern.ch/trac/lhcb/browser/DBASE/trunk/AppConfig/options/DaVinci/DV-RedoCaloPID-Stripping21.py.
Also the appropriate DB tags should be used (same as in s21 MC productions)

Moreover since this is usually done on flagged MC, also global cuts (stripping dependent) should be applied. In the case of S21 these options should be inserted at the beginning
# Tighten Trk Chi2 to <3 from CommonParticles.Utils import DefaultTrackingCuts DefaultTrackingCuts().Cuts = { "Chi2Cut" : [ 0, 3 ], "CloneDistCut" : [5000, 9e+99 ] }

Although the aim of this step is to tech about technical aspects I would also put a recommendation to contact MC and Stripping liaison before attempting any restripping of MC. There are details of which the users are not always aware.

[alexpearce]

This is great to have, thank you! Sounds like there are three things we need to add to the lesson:

1. A call-out saying something like “always contact your MC and stripping liaisons before restripping your MC. There may be details that are not covered in this lesson that you need to be aware of.”
2. Add the options files for the CALO reprocessing and a little explanation as to why they're needed.
3. Add the DefaultTrackingCuts and again explain why.

[acontu]

Glad to help!
Another small detail, not strictly related to this example is that if one wants to produce intermediate DSTs instead of going straight to ntuple extra options should be added to the DSTWriter conf as in:
https://svnweb.cern.ch/trac/lhcb/browser/DBASE/trunk/AppConfig/options/DaVinci/DV-Stripping21-Stripping.py

These options are at line 119 of the file above:
# Items that might get lost when running the CALO+PROTO ReProcessing in DV caloProtoReprocessLocs = [ "/Event/pRec/ProtoP#99", "/Event/pRec/Calo#99" ]
# Make sure they are present on full DST streams SelDSTWriterConf['default'].extraItems += caloProtoReprocessLocs

This is necessary to save the new protoparticles produced after the calo reprocessing (this will overwrite the previous one) so it is technically impossible to have a MC DST that is both consistent with s20 and s21.

[alexpearce]

Having a lesson on that would be very nice. We talked about it in the past in #7. I tried it in the past, but ran in to problems that I can't remember now. I'm +1 on getting the technique more widely known; it should make remaking ntuples much faster.