b Tag Data in CMSSW 1.6
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, ordered as in the original jet collection). 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. It also provides a reference to the TagInfo information, which is described later. The TagInfo is not needed for simple analyses.
The JetTag collections are labelled by the b tag algorithm that produced them. In CMSSW 1.6, the most important of these labels are:
- Track counting tag with N = 3: trackCountingHighPurJetTags
- Track counting tag with N = 2: trackCountingHighEffJetTags
- Jet probability tag: jetProbabilityJetTags
- Soft electron tag: softElectronJetTags
- Soft muon tag: softMuonJetTags
- Soft muon tag, not using muon impact parameter significance: softMuonNoIPJetTags
- Combined SV b tag: combinedSVJetTags
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. It also gives you the jet and the tracks associated with it. There are several different types of TagInfo object, for the various b tag algorithms. The
TrackIPTagInfo
is shared by both Track Counting and Jet Probability tags.
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.
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IanTomalin - 29 Oct 2007