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Option to apply b-tag aware OR only for electrons below pT threshold

Konstantin Lehmann requested to merge kolehman/athena:bTag-aware-OLR-only-for-some-electrons into 21.2

B-tag aware overlap removal has been seen to remove genuine electrons at high pT and instead keep an overlapping jet around. This is documented in a jira ticket and on a livepage. Current recommendations by the IFF are documented on the twiki.

This MR implements the suggested approach 2 from the twiki: use B-jet aware OR when electron pT < 100 GeV, no b-jet aware OR when ele pT > 100 GeV. The pT cut can be set with the property MaxElePtForBJetAwareOR in the EleJetOverlapTool. If set to negative values, b-tag aware OR is applied everywhere. To deactivate b-tag aware OR, BJetLabel can be set to an empty string.

The re-implementation has been tested by running it through the PAOD maker producing inputs for the high-mass HWW search (DSID 341016). The attached plots show the electron pT distribution. It can be seen that the configuration MaxElePtForBJetAwareOR=-1 reproduces the previous setup. Successively reducing the cut to 500, 200, 100 affects electrons in the corresponding pT range.

Note that the first bin also grows when lowering the cut. My suspicion is that these come from events with multiple electrons. Suppose that an even has two electrons that are in vicinity of the same b-tagged jet. When MaxElePtForBJetAwareOR is higher than both electron pTs, the b-jet is favoured and both electrons are removed. When MaxElePtForBJetAwareOR is smaller than the higher-pT electron, the jet is removed and both electrons will survive. This is a small effect, because most events have only one electron.

Number of events (electrons) passing the OR:

  • nominal: 2595 (2626)
  • -1 GeV: 2595 (2626)
  • 500 GeV: 3327 (3369)
  • 200 GeV: 3719 (3768)
  • 100 GeV: 3737 (3789)
Edited by Konstantin Lehmann

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