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Background determination in early data for single electron trigger. First look how to estimate background in early data and w hat useful can be extracted from first data Electron fake rate vs different physics process es. Electron container: - PowerPoint PPT Presentation
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e/ workshop in Hamburg
14-17 September 2008
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Background determination in early data for single electron
trigger
Oleg Fedin
• First look how to estimate background in early data and what useful can be extracted from first data
• Electron fake rate vs different physics processes
• Electron container:
Nel = Njets + Nconv + Nb,ce + NW,Z
Njets – fakes from jets
Nconv – conversion electrons (background electrons)
Nb,ce – electrons from b,c quarks (non isolated electrons)
NW,Z – electrons from W and Z decays (isolated electrons)
• Could we measure db,ce /dpT ?
• After tight cut (rel 13) :
• di-jet sample (5802 ET>17 GeV) Isolated 13% (W/Z~4:1); b,ce 58.3%; jet fakes 19.9%; conv. electrons 8.7%
• min. bias sample (5805 ET>8 GeV) b,ce 75.1%; jet fakes 18.5%; conv. electrons 6.4%
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• How to estimate jet fake contribution ? • TRT detector get possibility to identify electrons;• Varying TR ratio cut (#TR hits per track/#TRT hits
per track) try to suppress hadrons; • How to estimate conversion contribution?
• Conversion reconstruction algorithm (rel 14.2.20.2);• B-layer, E/p;
• How to estimate W,Z contribution?
• We ETmiss>25 GeV;
• Z ee events with two electrons;
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• egamma objects after tight cut
• TR ratio cut ~0.08 el~90%
~0.15 el~75%
5802 - di-jets
5802 - di-jets
5802 - di-jets-electrons- hadrons
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5805 - min bias
5805 - di-jets
• These plots most relevant to the first physics data (e10 trigger)
• To control background electrons relax B-layer and E/p cuts
• Purity = S/(S+B)• Signal (S) non isolated
electrons from b,ce • Background (B) include
jet fakes (hadrons) and conversion electrons
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5805 - min bias
5802 - di-jets
• Very difficult to extract separate contributions of b and c jets
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5802 - di-jets 5805 - min bias
Electron fake rates studies
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• Reminder: even in MC, fake rates from jets not yet understood as a function of physics processes
• Top plot - jets spectrum for the different data sample
• Bottom plot egamma object spectrum for the different data sample
DS5001 minbias (not filtr)DS5144 Z->eeDS5802 dijet (PT
Hard>15)DS5805 minbias (ET
filtr>6)DS5807 dijet (PT
Hard>35)
ETclus (GeV)
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• Illustration of kinematic ranges of truth jets and egamma objects in different physics sample
Jet rejection vs ETtruthJet
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DS5802 dijet (PTHard>15) ET
clus>17 GeVDS5805 minbias (ET
filtr>6) ETclus>8 GeV
DS5807 dijet (PTHard>35) ET
clus>35 GeVDS5001 minbias (not filtr) ET
clus>8 GeVDS5009 dijet (PT
Hard=8-17) ETclus>8 GeV
DS5010 dijet (PTHard=17-35) ET
clus>17 GeVDS5011 dijet (PT
Hard=35-70) ETclus>35 GeV
DS5144 Z->ee ETclus>8 GeV
• Clear seen threshold effects - compare di-jet data sample with PT
hard>35 (green triangle) and di-jet with PThard>17 (black
circle) • Jets spectrum due to QCD correction is more hard for Z->ee
data sample
Jet rejection vs ETtruthJet
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No cut on Etclus
DS5802 dijet (PTHard>15) ET
clus>17 GeVDS5805 minbias (ET
filtr>6) ETclus>8 GeV
DS5807 dijet (PTHard>35) ET
clus>35 GeVDS5001 minbias (not filtr) ET
clus>8 GeVDS5009 dijet (PT
Hard=8-17) ETclus>8 GeV
DS5010 dijet (PTHard=17-35) ET
clus>17 GeVDS5011 dijet (PT
Hard=35-70) ETclus>35 GeV
DS5144 Z->ee ETclus>8 GeV
Jet rejection vs ETcut
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DS5802 dijet (PTHard>15)
DS5805 minbias (ETfiltr>6)
DS5807 dijet (PTHard>35)
DS5001 minbias (not filtr)
DS5144 Z->ee
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Z-> eeDS5144
Min. bias DS5001
ETtruthjet> 8 GeV
Jet per event 2.82 0.62
light quark,% 32.3 25.4
b,c quark,% 8.8 6.7
gluon,% 54.4 62.7
not matched,% 4.5 5.2
ETtruthjet> 30 GeV
Jet per event 1.09 0.2
light quark,% 36.1 30.1
b,c quark,% 10.2 6.8
gluon,% 50.3 59.1
not matched,% 3.3 4.0
DS5001 Min bias
DS5144 Z->ee
• Matching truth jets to original parton quite complex (and frequently impossible
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Only gluon jets
light quark jets
b,c quark jets
• Need to understand why min bias Rg/Rq ~ 3 and Z->ee Rg/Rq ~ 2 and
BACK UP SLIDES
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Process DSPT
Hard, GeV
Filter,ET
jet
Eff. Filter,%
#Mevents
Cut ET
clus FRejection, medium cut
di jets 5802 >15 >17 8.28 8.4 >8 2.155 10012
>17 0.736 201810
di jets 5009 8-17 no 0.9 >8 0.955 156867
di jets 5010 17-35 no 0.4 >8 2.488 4228
>17 0.920 2953266
di jets 5011 35-70 no 2.8 >8 3.439 1511
>35 0.905 281693
di jets 5807 no >35 16.18 2.6 >8 3.056 6912
>17 1.862 9525
>35 0.862 189822
min bias 5805 no >6 5.7 4.1 >8 0.307 11728
>17 0.043 283986
min bias 5001 no no 3.2 >8 0.314 115539
>17 0.042 2307302
Z->ee 5144 no ETlep>10 0.2 >8 1.730 1292
>17 0.664 1143
Jet rejection vs ETtruthJet
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Jet rejection vs ETtruthJet
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Etclus > 8 GeV
Jet rejection vs ETClus
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