===== Recipe to Derive the Data Pile-Up Profiles  =====

   * The following two centrally produced files should be used:
            * the pile-up JSON file [[https://cms-service-dqm.web.cern.ch/cms-service-dqm/CAF/certification/Collisions12/8TeV/PileUp/pileup_JSON_DCSONLY_190389-208686_All_2012_pixelcorr.txt|pileup_JSON_DCSONLY_190389-208686_All_2012_pixelcorr.txt]]
            * the list of good lumi sections [[https://cms-service-dqm.web.cern.ch/cms-service-dqm/CAF/certification/Collisions12/8TeV/Reprocessing/Cert_190456-208686_8TeV_22Jan2013ReReco_Collisions12_JSON.txt|Cert_190456-208686_8TeV_22Jan2013ReReco_Collisions12_JSON.txt]]

   * The actual pile-up profile is easily generated with the command

   pileupCalc.py -i Cert_190456-208686_8TeV_22Jan2013ReReco_Collisions12_JSON.txt --inputLumiJSON pileup_JSON_DCSONLY_190389-208686_All_2012_pixelcorr.txt --calcMode true --minBiasXsec 69400 --maxPileupBin 60 --numPileupBins 60  DataPUProfile_2013Jan22.root

=== PU-Related Links and info ===

  * [[https://twiki.cern.ch/twiki/bin/viewauth/CMS/PileupJSONFileforData#2012_Pileup_JSON_Files|Here]] you can find info about PU JSON file for data
  * If you are interested in a specific run range then you have to filter the two JSON files above as described [[users:ngadiuba:tools:lumicalc|here]]
  * You can download directly the JSON files with the command

    wget --no-check-certificate https://cms-service-dqm.web.cern.ch/cms-service-dqm/CAF/certification/Collisions12/8TeV/Reprocessing/Cert_190456-208686_8TeV_22Jan2013ReReco_Collisions12_JSON.txt

===== How to calculate weights =====

  * Get the MC PU distribution for the scenario of interest from [[https://twiki.cern.ch/twiki/bin/viewauth/CMS/Pileup_MC_Gen_Scenarios|here]]
  * Then calculate the weights using the true number of PU interactions for the in-time bunch crossing. This information is extracted in CMSSW as follows

   Handle<std::vector< PileupSummaryInfo > >  PupInfo;
   event.getByLabel(edm::InputTag("addPileupInfo"), PupInfo);
   
   std::vector<PileupSummaryInfo>::const_iterator PVI;
   
   float Tnpv = -1;
   for(PVI = PupInfo->begin(); PVI != PupInfo->end(); ++PVI) {
   
      int BX = PVI->getBunchCrossing();
   
      if(BX == 0) { 
        Tnpv = PVI->getTrueNumInteractions();
        continue;
      }
   
   }
 
===== PUweight class for SFrame =====
  * [[users:ngadiuba:tools:puweightrecipe:puweighth|PUWeight.h]]
  * [[users:ngadiuba:tools:puweightrecipe:puweightcxx|PUWeight.cxx]]