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CMSSW Tutorial A. Nikitenko

This tutorial provides an in-depth introduction to event processing within the CMSSW framework, particularly focusing on processes relevant to tau identification. It covers essential steps such as event generation, digitization, local reconstruction, and high-level object reconstruction. Additionally, the tutorial details how to run CMSSW with ASAP, utilizing various modules like event generators (PYTHIA, HERWIG) and file management. Users will learn the importance of module interactions, configuration files, and complete pipeline examples to facilitate their analysis and research in particle physics.

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CMSSW Tutorial A. Nikitenko

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  1. CMSSW TutorialA. Nikitenko • Introduction • Example of reconstruction: “how to” • Running CMSSW with ASAP • Home work useful for tau id group

  2. Introduction

  3. Event processing: “physics” view • Event generation (in MC world) • Digitization • Local reconstruction • High level object reconstruction • Event selection • Event analysis

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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:

  10. 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

  11. 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

  12. 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

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

  14. 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

  15. 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

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

  17. Running CMSSW with GRID/ASAP • Instructions can be found on http://cmsdoc.cern.ch/~anikiten/cms-higgs/ASAP_CMSSW_job • Many thanks to ASAP team • Julia Andreeva • Olga Kodolova • Craig Munro • Juha Herrala

  18. Homework useful for tau id group • Compare two ways to suppress electron contamination to tau-jet : • cut on hottest HCAL tower ET in jet • cut on ETjet(hadr)/pTltr • Using instructions (see page 7) analyze single e and tau-jet of pT = 30-60 GeV, h < 2.2.

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