B-tagging reference plots

Complete: 2

Introduction

In this page you can find reference plots for b-tag performances. The plots give first of all the discriminator distribution and the efficiency versus rejection. Those plots can be used in analysis to chose the working points and cuts for analysis.

Please note that:

  • Each algorithm has a different discriminator distribution (cuts should be algorithm dependent!)
  • Different version of the software/algorithm can have different discriminator distribution
  • At different jet energy and eta the performances can be much different
  • Different samples/event topology may give much different performances (e.g. QCD vs TTbar)

Information on b-taggers

With early data "simple" taggers such as Track Counting, Simple Secondary Vertex and JetProbability(two variants) are recommended for use.

Track Counting and Simple Secondary Vertex taggers do not need any calibration constants so while running/re-running these taggers one need not worry about which global tag to use.

JetProbability taggers needs calibration constants. Recently these constants have been derived and uploaded to DB. The information on how to pick up these constants will be circulated soon.

Working/Operating points

The b-tag POG has defined working points "Loose " (L), "Medium" (M) and "Tight" (T) for 10%, 1% and 0.1% light mis tag : more details on these working points can be found on https://twiki.cern.ch/twiki/bin/viewauth/CMS/BTagPerformanceOP

Reference plots

MC Validation plots for recent releases published HERE can be taken as reference.

With Old CMSSW versions

To know details about the olde CMSSW versions click the link provided below.

How Reference plots are produced (you can produce yourself!)

All the following reference plots are created with the Analyzer in RecoBTag/Analysis package (full documentation).

The result of the Analyzer are histograms in configurable pt and eta bins for the various flavours. The analyzer produce a root file containing the histograms and optionally PostScript and gif files.

You can run the Analyzer on your sample by using the following cfg snippet:

  include "RecoBTag/Analysis/data/bJetTagAnalysis.cfi"

  replace bJetTagAnalysis.rootfile = "myBTagPerformanceHistograms.root"
  replace bJetTagAnalysis.jetTagModuleLabel = { "trackCountingHighEffJetTags", "trackCountingHighPurJetTags",
"jetProbabilityJetTags", "combinedSVJetTags","combinedSVMVAJetTags","impactParameterMVAJetTags" }

  path p = { bJetTagAnalysis}

More configuration option are listed in:
  • RecoBTag/Analysis/data/bTagAnalysis.cff
  • RecoBTag/Analysis/data/bJetTagAnalysis.cfi

Working points

The b-tag POG will soon define some working points for which is guaranteed that performances will be measured on data. An interface to access the working point information (cut, efficiency, rejection etc...) is under development.

CMSSW 1.6.X (QCD 50-80)

All histograms are available here:


cut-ref-dus.gifcut-ref-b.gif


Review status

Reviewer/Editor and Date (copy from screen) Comments
JyothsnaK - 19-Oct-2010 Added information on taggers
JyothsnaK - 14-Oct-2010 Updated the contents

-- AndreaRizzi - 20 Sep 2007: page author

Responsible: AndreaRizzi

Topic attachments
I Attachment History Action Size Date Who Comment
Unknown file formatroot cmssw161-500k-qcd5080.root r1 manage 8110.1 K 2007-09-20 - 10:04 AndreaRizzi CMSSW 16X b-tag performances, QCD 50-80, 500k events
GIFgif cut-ref-b.gif r1 manage 10.9 K 2007-09-20 - 10:12 AndreaRizzi  
GIFgif cut-ref-dus.gif r1 manage 11.3 K 2007-09-20 - 10:11 AndreaRizzi  
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Topic revision: r9 - 2011-06-11 - DanielBloch



 
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