Skimming

Skimming is a process in which we drop some uninteresting events from the ROOT trees. This page explains how to perform basic or advanced skimming with tea.

Basic skimming

Simple skimming can be achieved directly from the config file - you can apply basic cuts on event properties. There are two variables that control it - triggerSelection and eventCuts:

triggerSelection = (
    "HLT_IsoMu24",
)

eventCuts = {
    "MET_pt": (30, 9999999),
    "nMuon": (1, 9999999),
    "nGoodLeptons": (1, 9999999),
}

In the eventCuts you are also allowed to use your extraEventCollections - check out the tutorial page to learn more about it.

If you want to do simple skimming, have a look at My first skimmer tutorial.

Advanced skimming

Sometimes using existing branches and extra collections is not enough. In this case you will need to write a dedicated skimmer app. Fortunately, you don’t have to start from scratch - use create.py script to create and app. This will create a skeleton for you that contains a baseline for your custom skimmer, giving you the full freedom of accessing any default and extra collections, performing any operations/selections you want, and saving surviving events to the output file.

If you’re into custom skimming, you may also be interested in custom physics objects and custom events that will make your code cleaner and will help you organize your skimming app.