Extra event collections

Let’s say we want to produce a ROOT file with 2 histograms: transverse momenta and pseudorapidity of leptons (e/μ) with φ ∈ (0, 2) from backgrounds_dy.root file.

Prepare config file

For this we can use the existing histogrammer app and copy the example histogrammer config:

cp tea/configs/examples/histogrammer_config.py configs/my_histogrammer_config.py

We will use a feature called extraEventCollections to achieve our goal. It allows us to define new collections on the fly. All we need to provide are:

• The name of the new collection.
• Input collections.
• (Optional) selections on variables that exist in all input collections.

For instance, it could look like this:

extraEventCollections = {
    "GoodLeptons": {
        "inputCollections": ("Muon", "Electron"),
        "phi": (0., 2.),
    },
}

Then, you can define default histograms using this collection:

defaultHistParams = (
#  collection      variable          bins    xmin     xmax     dir
  ("GoodLeptons" , "pt"            , 400,    0,       200,     ""  ),
  ("GoodLeptons" , "eta"           , 100,    -2.5,    2.5,     ""  ),
)

Build & run

Then, build the project and run histogrammer, specifying the corresponding config file:

source /tea/build.sh
cd bin
./histogrammer --config my_histogrammer_config.py

Have a look at the output file - you should see histograms of lepton pt and η, only for leptons with φ ∈ (0, 2).