LHCb Stripping FAQ - Re-Stripping of MC in MicroDST format

Restrictions

In the case where your MC is persisted in the DST format, reconstruction information of the entire event is saved. This is not the case for MicroDST MC. It is unlikely, that re-stripping will result in the same data-sample that you would have got if you applied your stripping line during production. However, there is an algorithm in the MicroDST production that copies reconstruction information matched to signal MC-Particles. To check whether that algorithm ran during your production, see DUMMY. It is important to note that the candidates you can get out of your MicroDST either passed any stripping line or are truth-matched (associated to the signal MC particles). This is different to DST, where you can in principal get every candidate.

All calculation requiring information of more than the candidate only, like Isolation variables in RelatedInfoTools, cannot be performed during MicroDST Re-stripping and must be left out.

How To

Firstly, one has to check whether that algorithm ran during the production. Therefore, look at the Option files of your production (can be found in the bookkeeping) and check whether the "isMC" flag is set to true in stripMicroDSTElements and in stripMicroDSTStreamConf in the SelDSTWriter algorithm. In most cases the Writer is defined in "$APPCONFIGOPTS/DaVinci/DV-Stripping-MC-muDST.py".

Check out Packages

To make the necessary changes to your stripping line (remove RelatedInfoTools and such, changing cuts), check out the right DaVinci and your desired stripping package (StrippingSelections or StrippingArchive). My example will use StrippingSelections, which should be equivalent to StrippingArchive if you checkout the right version of stripping (see release notes of your DaVinci version).

 lb-dev DaVinci/vXXrXpX 
 cd ./DaVinciDev_vXXrXpX 
 git lb-use Stripping 
 git lb-checkout Stripping/vXXrXXpX Phys/StrippingSelections

Next up, you also need to checkout CommonParticles (CommonParticlesArchive):

 git lb-use Phys 
 git lb-checkout Phys/vXXrXXpX Phys/CommonParticles

Making the necessary changes

self.phi2MuMuControlLine = StrippingLine(PhimumuControl_name+'Line',
                                           prescale = config['Phi2MuMuControlPrescale'],
                                           postscale = config['Postscale'],
                                           RelatedInfoTools = config['RelatedInfoTools_Phi2MuMuControl'],
                                           MDSTFlag = False,
                                           #RequiredRawEvents = ['Velo', 'Muon', 'Calo'],
                                           algos = [ self.selPhi2MuMuControl ]
                                           )

-- NiklasStefanNolte - 2018-02-20