Measurements of Electron Charge Mis-identification Rate
and Electron Efficiency within SUSY analysis framework
1
Zhichao Zhan SDU
Shan Jin IHEP
Xueyao Zhang SDU
Emmanuel Monnier CPPM
FCPPL
April 7, 2011
Jinan,China
outline
 Introduction
 Tag-and-Probe Method
 Electron Charge Misidentification Rate
 Electron Reconstruction Efficiency
 Conclusion and Prospect
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Introduction
 ATLAS SUSY group has published 2 paper 0lepton channel and 2 lepton channel.
 Charge mis-identification is the very important part for SUSY 2 same sign lepton final
states analysis, which is also an important issue for the physics channel that has lepton
charge requirement (SS/OS).
 Several constituents for charge misidentification
Bremsstrahlung;Conversion events;fake electron from jet
 We try to get a precise charge misidentification rate.
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Tag-and-probe Method
1.Good Events(pls see the Appendix)
2. 2 good electrons, one tight tag
electron; one probe electron.
3.MissingEt<20GeV
4.dphi(e1,e2)>pi*3/4
Data control sample is fitted by Breit Weigner function
convoluted with Gaussian distribution function (Line
shape); The background is fitted by Chebyshev
polynomials.
Definition:
N ss

;
N ss  N os
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4
Working
progress
Line
shape
Object and Bakground check:
Electron:Author=1||3; pt>20GeV
fabs(ηcalo)<2.47; etcone20<10GeV;ptcone30/pt<0.2
RubustMedium;
Electron eta
Electron pt
Working
progress
Data and MC
check
Electron phi
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There is no
significant
discrepancy
between MC and
data.
Electron charge mis-ID rate
data~34.3pb-1 @7TeV
RobustMedium
RobusterTight
DATA
Left: opposite sign events
fitted by line shape
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right: same sign events fitted
by line shape
RobustMedium
RobusterTight
MC
Apply the same fit process to MC Zee sample
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Electron charge mis-ID rate summary
|DATA-MC|(%)
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RobustMedium
RobusterTight
0.09±0.24
0.33±0.18
Electron efficiency using the same technique
RobustLoose
RobustMedium
RobusterTight
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9
Left: the probe electron
fulfill three level
selection criteria
Right: the probe electron
does not pass three level
selection criteria
Working
progress
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10
Working
progress
Positron efficiency
RobustLoose
RobustMedium
RobusterTight
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11
Left: the probe positron
fulfill three level
selection criteria
Right: the probe positron
does not fulfill three level
selection criteria
Working
progress
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12
Working
progress
No difference between positron and electron
efficiency
Conclusion&Prospect
Electron charge misidentification rate and electron
reconstruction efficiency from Tag-and-Probe method
sounds reasonable.
Using Tag-and-probe method, we can get a charge misidentification rate with respect to bin-by-bin pt distribution,
when we have enough data statistics.
The discrepancy of electron charge misID rate between real
data and MC is under investigation
Thanks a lot!
Merci ~
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Appendix I
Lepton
 Electron :






Author=1||3; pt>20GeV
fabs(η2calo)<2.47; etcone20<10 GeV;ptcone30/pt<0.2
RubustMedium&&ExpectHitBLayer;
Muon:
Staco combined; 0<=matchChi2<=100
fabs(η)<2.5; pt>20GeV; etcone20<10 GeV;

Jet&MET
 Jet:
 AntiKt4Topo; EMJES calibration;

pT>20 GeV, fabs(η)<2.5
 MET:
MET_LocHadTopo
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 Jet Cleaning: remove events with any jes with pt(EM)>10GeV,satifying:




emf>0.95 && fabs(quality)>0.8
n90<=5 && hecF>0.8
|t|>=50ns
hecF >= 1 - fabs(quality)
Step1:GRL
Step2:Trigger
Step3:Jet Cleaning
Step4:Vertex requirment(Ntrack>4)
Step5:Veto events with crack electrons
Step7:OR for jets/electrons(remove jets within dR=0.2 of an
electron)
Step8:Veto events with electron in bad OTX regions
Step9:Veto events with muon having|Z0-Zpv|>10mm
Step10:Remove electrons/muons within dR=0.4 of a jet
Note:
use electron cluster(eta,phi)for OTX veto
use electron object(eta,phi)for OTX veto
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Appendix II
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Appendix III
RobustMedium
tight
Truth tag mis-charge rate.
Strategy：
1. Selecte an Electron,which fulfill with pt >20GeV,|eta|<2.47,isEM_tight,
2. author==1||author==3
3. Tag a truth Electron fufill match(dR<0.1)
4. Calculate its mischarge rate.
pmis 
mis  assigned electron
all electrons
Working
progress
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Working
progress
Working
progress
The charge mis-identification rate from reconstruction is
around 0.8%,in the truth tag method measurement
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