====== Inclusive Vertex Finder (IVF) ======

The IVF will run out-of-the-box in CMSSW_5_3_11. If unsure, you can check out the following two packages:

  cvs co -r V02-02-06 RecoVertex/AdaptiveVertexFinder
  cvs co -r V01-10-02 RecoBTag/SecondaryVertex

To use the same approach as the VHbb group, one also needs to check out two additional packages:

  cvs co -d IVF/BCandidateProducer UserCode/BbCorrelation/CMSSW/BAnalysis/BCandidateProducer
  cvs co -d ZSV/BAnalysis UserCode/ZSV/BAnalysis/
  scram b -c

Last command needed to update really old IVF package config files to BuildFile.xml files.

===== Work flow =====

==== General vertexing ====

In order to get the IVF to work one has to perform inclusive vertexing by including [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/python/inclusiveVertexing_cff.py|inclusiveVertexing_cff.py]]:

  process.load('RecoVertex/AdaptiveVertexFinder/inclusiveVertexing_cff')

The IVF runs on pre-selected vertices. After a coarse pre-clustering based on track distances and angles, vertices are reconstructed with the Adaptive fitter (outlier resistant, iterative procedure). This is done using the inclusive vertex finder from the [[https://github.com/cms-sw/cmssw/tree/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder|adaptive vertex finder package]]:

  * Source code: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/plugins/InclusiveVertexFinder.cc|InclusiveVertexFinder.cc]]
  * Configuration file: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/python/inclusiveVertexFinder_cfi.py|inclusiveVertexFinder_cfi.py]]

These vertices are then merged depending on their significance in distance and the fraction of tracks they share (in particular vertices with a large fraction of common tracks are merged):

  * Source code: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/plugins/VertexMerger.cc|VertexMerger.cc]]
  * Configuration file: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/python/vertexMerger_cfi.py|vertexMerger_cfi.py]]
  * using the standard config:
    * maxFraction = 0.7
    * minSignificance = 2

In the next step it is made sure that all tracks belong either to a secondary vertex or the primary vertex only optimising the assignment of tracks to vertices, followed by another vertex fit:

  * [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/plugins/TrackVertexArbitrator.cc|TrackVertexArbitrator.cc]]
  * [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/python/trackVertexArbitrator_cfi.py|trackVertexArbitrator_cfi.py]]

These refitted vertices are then again merged depending on their significance in distance and the fraction of tracks they share:

  * Source code: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/plugins/VertexMerger.cc|VertexMerger.cc]]
  * Configuration file: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/python/vertexMerger_cfi.py|vertexMerger_cfi.py]]
  * config is overwritten by [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/python/inclusiveVertexing_cff.py|inclusiveVertexing_cff.py]] to:
    * maxFraction = 0.2
    * minSignificance = 10

==== b-vertex filtering ====

The optimised vertices undergo a b-vertex filter:

  * Source code: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoBTag/SecondaryVertex/plugins/BVertexFilter.cc|BVertexFilter.cc]]
  * Configuration file: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoBTag/SecondaryVertex/python/bVertexFilter_cfi.py|bVertexFilter_cfi.py]]

==== b to charm decay vertex merging ====

The b-to-charm decay vertex merging attempts to identify B to D meson decays and merges them based on DeltaR, the vertex mass, the angle between them and the relative transverse momentum:

  * Source code: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoBTag/SecondaryVertex/plugins/BtoCharmDecayVertexMerger.cc|BtoCharmDecayVertexMerger.cc]]
  * Configuration file: [[https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoBTag/SecondaryVertex/python/bToCharmDecayVertexMerger_cfi.py|bToCharmDecayVertexMerger_cfi.py]]

===== Useful links =====
partly used in VHbb ntuples:
  * VHbb recipe: https://twiki.cern.ch/twiki/bin/viewauth/CMS/VHbbAnalysisNewCode#NtupleV42_CMSSW_5_3_3_patch2
  * http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/VHbbAnalysis/HbbAnalyzer/test/patData.py?revision=1.9&view=markup

Carlotta's code:
  * http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/ZSVAnalysisForPaper/ZSVAnalysis/zsvanalysisforpaper_MCfall11_DYc_cfg.py?revision=1.1&view=markup
  * http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/ZSVAnalysisForPaper/BCandidateProducer/plugins/BCandidateProducer.cc?revision=1.1&view=markup

twiki documentation:
  * official recipe: https://twiki.cern.ch/twiki/bin/viewauth/CMS/InclusiveVertexFinderRecipes
  * combination with CSV tagger: https://twiki.cern.ch/twiki/bin/viewauth/CMS/CSVIVF

CMSSW:
  * https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoVertex/AdaptiveVertexFinder/
  * https://github.com/cms-sw/cmssw/blob/CMSSW_5_3_X/RecoBTag/SecondaryVertex/
===== Current errors =====

none


===== Steps for MSSM Hbb analysis ===

  cvs co -r V02-02-06 RecoVertex/AdaptiveVertexFinder
  cvs co -r V01-10-02 RecoBTag/SecondaryVertex
  
Replace ''PhysicsTools/PatAlgos/python/tools/jetTools.py'' by this [[https://twiki.cern.ch/twiki/pub/CMS/InclusiveVertexFinderRecipes/jetTools.py.txt|version]].

Check for details of information:
  RecoBTag/SecondaryVertex/test/runIVFAnalyzer_cff.py
  RecoBTag/SecondaryVertex/test/IVFAnalyzer.cc
  
And voila:

  The bdiscriminators below will be written to the jet collection in the PATtuple (default is all, see PatAlgos/PhysicsTools/python/tools/jetTools.py)
  jetBProbabilityBJetTags
  jetProbabilityBJetTags
  trackCountingHighPurBJetTags
  trackCountingHighEffBJetTags
  simpleSecondaryVertexHighEffBJetTags
  simpleSecondaryVertexHighPurBJetTags
  simpleInclusiveSecondaryVertexHighEffBJetTags
  simpleInclusiveSecondaryVertexHighPurBJetTags
  combinedSecondaryVertexBJetTags
  combinedSecondaryVertexMVABJetTags
  softMuonBJetTags
  softMuonByPtBJetTags
  softMuonByIP3dBJetTags
  simpleSecondaryVertexNegativeHighEffBJetTags
  simpleSecondaryVertexNegativeHighPurBJetTags
  negativeTrackCountingHighEffJetTags
  negativeTrackCountingHighPurJetTags
  combinedInclusiveSecondaryVertexBJetTags
  combinedMVABJetTags
  doubleSecondaryVertexHighEffBJetTags