How to Access
PAT Candidate Information
PAT Tutorial CERN December 2012
lecturer: Andreas Hinzmann (CERN)
tutors: Guillermo Breto (UCD),
Sudhir Malik (Nebraska)
and the PAT tutorial team
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The Pat Tuple
In the morning section you have learned:
how to find documentation
 how to produce PAT Tuples
 how to inspect your configuration file
 how to customize the PAT Tuple workflow
 how to look at the PAT Tuple Event Content

Now you will learn how to access to PAT Tuples produced in
order to perform you analysis.
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The Pat Tuple
A PAT Tuple is and EDM file:
Root file with predifined file structure
 Trees of CMS customized DataFormats (Muon, Electron, Track)

TBrowser
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edmDumpEventContent
Example pat::Muon
Typical class structures for HEP Collaborations
http://cmssdt.cern.ch/SDT/doxygen
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Access PAT Tuple
Access is as to normal Root file.
 PAT provides also more appropriate access methods:



Analysis performed directly on PAT Tuples (BasicAnalyzer concept)

Within the Full Framework (EDAnalyzer)

With FW Lite (FWLiteAnalyzer)
Production of flat ntuples (again EDM files  )
 Analysis performed with your root macros or FW/FWLite analyzer
EDMTuple
PAT Tuple
EDAnalyzer
Full framework
FWLiteAnalyzer
FWLite
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BasicAnalyzer Concept
Decide late whether you want to use FWLite or full framework
 Write the code to be compatible with both

BasicAnalyzer
PAT Tuple
EDAnalyzer
Full framework
FWLiteAnalyzer
FWLite
https://twiki.cern.ch/twiki/bin/view/CMSPublic/WorkBookFWLiteExamples#ExampleFive
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Example PatMuonAnalyzer
Class declaration:
Your class inherits from BasicAnalyzer class
http://cmssw.cvs.cern.ch/cgibin/cmssw.cgi/CMSSW/PhysicsTools/PatExamples/interface/PatMuonAnalyzer.h?r
evision=1.1&view=markup&pathrev=V00-05-26
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Example PatMuonAnalyzer
Class implementation:
http://cmssw.cvs.cern.ch/cgibin/cmssw.cgi/CMSSW/PhysicsTools/PatExamples/src/PatMuonAnalyzer.cc?revision=1.1
8
&view=markup&pathrev=V00-05-26
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FWLite or Full Framework?
BasicAnalyzer


...
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Very easy to wrap the
same code into one or the
other
Keep both if you like and
use what fits best to the
current purposes
Recommendations
FWLite:
Use this if you need quick turn around, when the analysis task is not too
complex (would also fit to a single EDAnalyzer), when you can still
handle all objects that you create and destroy on your way...
Full Framework:
Use this when the analysis tasks grow complex, when you intend to use
crab or batch systems, when you intend to use the edm::Event to
manage the amount of objects that you create and use on the way,
when you want flexible (plugin-wise) use of your code...
Advantage of both over you private solution:
Easy implementation, easy to learn and to understand, easy to maintain,
maximal use of CMSSW infrastructure (i.e. DataFormats, TFileServise,
Event management e.g. no event double counting)...
10
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How to run the examples:

Full Framework:

FWLite:
https://twiki.cern.ch/twiki/bin/view/CMSPublic/WorkBookPATAccessExercise
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The EDM-Tupleizer
The Analysis Tools Group (AT) also provides pre-written tools
and recommendations to make fully EDM complient flat ntuples:
 the CandViewNtpProducer:
 It is a generic ntuple dumper
 Easy to configure
 Don‘t need to write c++ code to produce your flat ntuples from
your PAT Tuples 
 More info and examples in the Twiki:
https://twiki.cern.ch/twiki/bin/view/CMSPublic/SWGuideEDMNtuples
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The EDM-Tupleizer

Easy access via string parsing to
variables you want to store in your flat
ntuple
https://twiki.cern.ch/twiki/bin/view/CMSPublic/SWGuideEDMNtuples
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The EDM-Tupleizer Output

The output is a full edm compliant edm Tuple, you can inspect it
as it was a standard PAT Tuple... It is still and EDM file :
TBrowser
edmDumpEventContent
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The EDM-Tupleizer Output
Analyze your EDM flat ntuple with an interactive/compiled
root macro
 Or use FWLite/full framwork to make use of full CMSSW
capabilities.
 In the Exercise 4 you will find a guideline to deal with EDM
flat ntuples

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Remark
General Remark:
 As you see AT covers a broad bunch of use cases for analysis from
smallest scale/complexity to largest scale/complexity.
 You can make use of easy access to data information, and a whole
bunch of Services and tools (TFileService, PAT features, Candidate Tools, HepMC
tools, POG tools)
 All these tools are established, accepted collaboration wide, tested,
maintained, ...
 ~50 people are working hard to make CMSSW your analysis software
(compare this to the manpower situation in your university)
 Don't waist your time on the re-invention, re-developement,
maintainance of you own private framework, spent your time on
physics!
 On the other hand there is always room for developments/improvement.
Joining AT developments is rewarded (Credit by points).. So, don‘t
hesitate if you wish to contribute 

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Final Remark

Everything which has been discussed here is part of Exercise 4.
Take your time to go through it and enjoy!
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