b Tag Data in CMSSW 1.3 & 1.4

The full data format is described here in the CMSSW Offline Guide. However, this section gives you an overview.

Each b tag algorithm produces a collection of JetTag and TagInfo objects (one for each jet). For most physics analyses, you will only need to access the JetTag object:


This gives the b tag discriminator value and references (links) to both the jet and its associated tracks.

The JetTag collections are labelled by the b tag algorithm that produced them. In CMSSW 1.3 & 1.4, the most important of these labels are:

  • Track counting tag with N = 3: trackCountingHighPurJetTags
  • Track counting tag with N = 2: trackCountingHighEffJetTags
  • Soft electron tag: softElectronJetTags
  • Soft muon tag: softMuonJetTags

For a full list of these labels in any CMSSW version, see the file RecoBTag/Configuration/data/RecoBTag_EventContent.cff .

The TagInfo contains the variables, such as track impact parameter significance, from which the b tag discriminator was calculated. Many simple physics analyses will never need to look at it. The TagInfo also gives you the jet and the tracks associated with it. And in CMSSW 1.3, it gives you a link to the JetTag that was calculated from it. There are several different types of TagInfo object, for the various b tag algorithms.


The b tag algorithms also rely on the association of tracks with jets. This information is stored in JetTracksAssociation. However, it can be accessed by the JetTag or TagInfo classes, so you should not need to worry about this.

-- IanTomalin - 22 Oct 2007

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng 130_JetTag.png r1 manage 4.3 K 2007-10-22 - 14:20 IanTomalin  
PNGpng 130_TagInfo.png r1 manage 10.0 K 2007-10-30 - 19:06 IanTomalin  
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Topic revision: r6 - 2011-12-06 - KatiLassilaPerini



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