Difference: BTaggingSystematics (9 vs. 10)

Revision 102014-09-26 - MartinZurNedden

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META TOPICPARENT name="TopLHCWG"

Treatment of the Correlations in b-Tagging Systematics in ATLAS and CMS

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    • ATLAS:
      • tag counting: fit b-jet efficiency on tagged jets multiplicity (only for 7 TeV data)
      • Kinematic selection and tag&probe: based on sample composition estimates
Changed:
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      • combinatorial likelihood PDF approach (only 8 TeV data), most precise measurement
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      • combinatorial likelihood PDF approach (only 8 TeV data), most precise measurement
 
      • kinematic fit: use a kinematic fit to reconstruct the final states and increase the purity of the sample
    • CMS:
      • Tag counting techniques (inclusive in pT)
Line: 112 to 112
 
  • Final usage: combination of calibrations
    • ATLAS:
      • various combinations of the calibrations provided among di-jets (pTrel, S8) and ttbar calibraions
Changed:
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      • default calibration is a combination of di-jet (S8) and ttbar (PDF-method)
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      • default calibration is a combination of di-jet (S8) and ttbar (PDF-method)
 
      • the choice of the combination is up to the individual analysis teams
      • global fit with all systematic uncertainties as nuisance parameters which can shift the mean data/MC SF
      • systematic uncertainties can be fully correlated or uncorrelated in each single kinematic bin or across kinematic bins
Line: 192 to 192
 
  • Analyses should merge the charm-to-light systematics with the b-fragmentation systematics into one systematics
    • we have then only five systematics left for the combination: b/c production, muon pT, charm-to-light ratio + b-fragmentatin, PS, ISR/FSR
  • Resulting five uncertainties of final result can be combined taking into account the correlations among the experiments
Changed:
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  • Summary table (for all six systematcs):
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  • Summary table (for all six systematics, 8 TeV data):
 
source size at ATLAS size at CMS
Changed:
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b/c prod. low pT: 0.1% - 0.2%, high ph: 1.2% - 2.0% low pT: 0.1% - 0.3%, high ph: 0.5% - 1.3%
mu pT low pT: 0.8% - 2.7%, high ph: 0.2% - 0.8% low pT: 0.1% - 1.1%, high ph: 0.1 - 0.9%
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b/c prod. low pT: 0.1% - 0.2%, high pT for b-prod.: 1.2% - 2.0% low pT: 0.1% - 0.3%, high pT: 0.5% - 1.3%
mu pT first pT bin: 2.5%, 0.2% - 0.9% elsewhere low pT: 0.1% - 1.1%, high pT: 0.1 - 0.9%
 
c/l ratio <0.1% - 0.2% <0.1% - 0.2%
b-frag 0.2% - 2.7% 0.2% - 0.8%
Changed:
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PS 0.1% - 4.1% 0.3% - 0.6%
IFSR 0.1% - 4.1% 0.3% - 0.6%
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PS 0.1% - 1.5% 0.3% - 0.6%
IFSR 0.3% - 1.4% 0.3% - 0.6%
 

Systematic Breakdown

 
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