What is in the datafiles?

Overview

Teaching: 5 min
Exercises: 5 min

Questions

How do I inspect these files to see what is in them?

Objectives

To be able to see what objects are in the data files

To be able to see how big these files are and how much space these object take up.

This part of the lesson will be done from within either a Docker container or VM. All commands will be typed inside that environment.

Setting up your CMSSW area

If you completed the lessons on virtual machines or Docker you should already have a working CMSSW area.

If you are using the VM:
- turn on your virtual machine and go to the right shell according to the validation instructions:
If you are using Docker:
- Start the container with:
```
docker start -i <theNameOfyourContainer>
```

Make sure you change directories to the CMSSW_5_3_32/src area; for instance, in Docker:

cd /home/cmsusr/CMSSW_5_3_32/src

Note that we are not really “installing” CMSSW but setting up an environment for it. CMSSW was already installed. This is why every time you open a new shell you will have to issue the cmsenv command, which is just a script that runs to set some environmental variables for your working area:

cmsenv

edmXXX tools

CMS uses a set of homegrown tools to interact with the AOD format, all of which are prefixed by edm, which stands for Event Data Model. We will not show you all of them, but introduce a few to give you an idea of what can be done.

edmDumpEventContent

The edmXXX tools take as an argument the full path to a file. Following a similar approach to the previous module, we’ve chosen one of the Monte Carlo files to test, but these commands would equally well with a data file.

Let’s start by using edmDumpEventContent and looking at the options

edmDumpEventContent --help

Usage: edmDumpEventContent [options] templates.root
Prints out info on edm file.

Options:
  -h, --help      show this help message and exit
  --name          print out only branch names
  --all           Print out everything: type, module, label, process, and
                  branch name
  --lfn           Force LFN2PFN translation (usually not necessary)
  --lumi          Look at 'lumi' tree
  --run           Look at 'run' tree
  --regex=REGEX   Filter results based on regex
  --skipping      Print out branches being skipped
  --forceColumns  Forces printouts to be in nice columns

We will first use edmDumpEventContent to see what is in one of these files with no other options. It may take 15-60 seconds to run and there will be a lot of output. You may find it useful to redirect the output to a file and then look at it there using less or a similar command (you can exit less by typing q).

edmDumpEventContent root://eospublic.cern.ch//eos/opendata/cms/MonteCarlo2012/Summer12_DR53X/TTJets_SemiLeptMGDecays_8TeV-madgraph/AODSIM/PU_RD1_START53_V7N-v1/10000/EA978C41-27D1-E211-9424-003048D46016.root > test_edm_output.log

less test_edm_output.log

Type                                  Module                      Label             Process
----------------------------------------------------------------------------------------------
LHEEventProduct                       "source"                    ""                "LHE"
GenEventInfoProduct                   "generator"                 ""                "SIM"
edm::TriggerResults                   "TriggerResults"            ""                "SIM"
vector<int>                           "genParticles"              ""                "SIM"
vector<reco::GenJet>                  "ak5GenJets"                ""                "SIM"
vector<reco::GenJet>                  "ak7GenJets"                ""                "SIM"
vector<reco::GenJet>                  "kt4GenJets"                ""                "SIM"
vector<reco::GenJet>                  "kt6GenJets"                ""                "SIM"
vector<reco::GenMET>                  "genMetCalo"                ""                "SIM"
vector<reco::GenMET>                  "genMetCaloAndNonPrompt"    ""                "SIM"
.
.
.
vector<reco::TrackExtra>              "tevMuons"                  "firstHit"        "RECO"
vector<reco::TrackExtra>              "tevMuons"                  "picky"           "RECO"
vector<reco::TrackExtrapolation>      "trackExtrapolator"         ""                "RECO"
vector<reco::TrackJet>                "ak5TrackJets"              ""                "RECO"
vector<reco::Vertex>                  "offlinePrimaryVertices"    ""                "RECO"
vector<reco::Vertex>                  "offlinePrimaryVerticesWithBS"   ""                "RECO"
vector<reco::VertexCompositeCandidate>    "generalV0Candidates"       "Kshort"          "RECO"
vector<reco::VertexCompositeCandidate>    "generalV0Candidates"       "Lambda"          "RECO"

You can get from this information the names of physics objects you may be interested in (e.g. ak5TrackJets) as well as what stage of processing they were produced at (SIM is for simulations and RECO is for reconstruction).

This information can be useful when writing your analysis code, which will be discussed in a later lesson.

Some of the other command-line options can be useful as well to filter the information.

Challenge!

Try the following options (with the same file) and see what it gives you. Can you see why this might be useful?

edmDumpEventContent --regex=Muon root://eospublic.cern.ch//eos/opendata/cms/MonteCarlo2012/Summer12_DR53X/TTJets_SemiLeptMGDecays_8TeV-madgraph/AODSIM/PU_RD1_START53_V7N-v1/10000/EA978C41-27D1-E211-9424-003048D46016.root

edmDumpEventContent --name root://eospublic.cern.ch//eos/opendata/cms/MonteCarlo2012/Summer12_DR53X/TTJets_SemiLeptMGDecays_8TeV-madgraph/AODSIM/PU_RD1_START53_V7N-v1/10000/EA978C41-27D1-E211-9424-003048D46016.root

Key Points

It’s useful to sometimes inspect the files before diving into the full analysis

Some files may not have the information you’re looking for

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