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CMSSW Tutorial

Learn about CMSSW event processing from generation to analysis using modules and sequences in this comprehensive tutorial.

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CMSSW Tutorial

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  1. CMSSW Tutorial

  2. Event processing: • Event generation (in MC world) • Digitization • Local reconstruction • High level object reconstruction • Event selection • Event analysis

  3. Event processing: CMSSW view • Event processing is a sequence of modules • Type of CMSSW modules: • Source • Event generator: PYTHIA, HERWIG, … • File containing some data for further processing • MC info • Digi • ….. • EDProducer • EDFilter • OutputModule • EDAnalyzer

  4. Event processing: CMSSW view Important to know one of the CMSSW rules: object produced in one module can not be updated/modified in other module

  5. How to run it • Command cmsRun –p name.cfg run event processing • User file name.cfg define modules that user want to run and sequence of running (path) • .cfg file is configuration file which uses CMS program configuration language https://uimon.cern.ch/twiki/bin/view/CMS/ConfigurationFileUsage

  6. Example: gen + sim-digi-reco in one step + analysis • Full example can be found on http://cmsdoc.cern.ch/~anikiten/cms-higgs/CMSSW/allReco • I will show you now only few elements • Jet reconstruction • Analysis (access to information) with “Framework analyser”. Code fragments shown on the next slides are taken from allReco.cfg

  7. Source module (or POOL Source) • I have generated already some events (di-taus, back-to-back) and store them into mcpool.root file. This file is “source module” for further event processing Standard name

  8. Module creating “raw” Calo Towers Module name; user defines it. Name of c++ class in CMSSW who produces Calo towers Code above could be put into .cfi file and this file can be included in .cfg as:

  9. Module creating Calo Towers used for jet finder Module name; user defines it. Name of c++ class in CMSSW who produces Calo Towers used by jet finder module caloTowers = CaloTowerCandidateCreator { string src = towerMaker” double minimumEt = 0.5 double minimumE = 0.8 } Name of the module who produced “raw” Calo Towers; see previous slide

  10. Module creating jets Module name; user defines it. Name of c++ class in CMSSW who produces Calo Towers used by jet finder Name of the module who produced Calo Towers to be used by jet finder; see previous slide

  11. Output Module User name to be used later Standard name names of modules produced objects user does not want to be stored into output file User name of output file

  12. Event processing steps: path • Few modules can be combined as sequence • Modules and sequences define path: sequence of processing steps output module name

  13. Analysis of output root file • bare root - no CMSSW libs needed • FWlite mode - few CMSSW libs needed • Analysis in a Framework analyzer • cmsRun –p name.cfg • name.cfg is user configuration file to run analysis • analysis uses full CMSSW framework See on the next slides example of full Framework analysis

  14. analysis.cfg user name Output file from previous step modules which produced objects in previous step to be analyzed now Name of c++ class performing analysis’ user access info and fill/store histos there

  15. Access event data in Analyzer (Analyzer.cc)

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