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Estimating Background Electron Rates in Early Physics Data

Explore methods to estimate background electrons in early data, discerning fake rates, and extracting useful information for single electron triggers. The text covers techniques to estimate jet fake and conversion contributions, control background electrons, and analyze electron fake rates.

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Estimating Background Electron Rates in Early Physics Data

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  1. Background determination in early data for single electron trigger • 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 Oleg Fedin

  2. Electron container: Nel = Njets + Nconv + Nb,ce + NW,Z Njets – fakes from jets Nconv – conversion electrons (background electrons) Nb,ce – electrons from b,c quarks (non isolated electrons) NW,Z – electrons from W and Z decays (isolated electrons) • Could we measure db,ce/dpT ? • After tight cut (rel 13) : • di-jet sample (5802 ET>17 GeV) Isolated 13% (W/Z~4:1); b,ce 58.3%; jet fakes 19.9%; conv. electrons 8.7% • min. bias sample (5805 ET>8 GeV) b,ce 75.1%; jet fakes 18.5%; conv. electrons 6.4%

  3. 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? • We ETmiss>25 GeV; • Z ee events with two electrons;

  4. egamma objects after tight cut • TR ratio cut ~0.08 el~90% ~0.15 el~75% • 5802 - di-jets • electrons • hadrons 5802 - di-jets 5802 - di-jets

  5. 5805 - di-jets 5805 - min bias • These plots most relevant to the first physics data (e10 trigger) • To control background electrons relax B-layer and E/p cuts

  6. 5802 - di-jets • Purity = S/(S+B) • Signal (S) non isolated electrons from b,ce • Background (B) include jet fakes (hadrons) and conversion electrons 5805 - min bias

  7. 5802 - di-jets • Very difficult to extract separate contributions of b and c jets 5805 - min bias

  8. Electron fake rates studies • 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->ee DS5802 dijet (PTHard>15) DS5805 minbias (ETfiltr>6) DS5807 dijet (PTHard>35) ETclus (GeV)

  9. Illustration of kinematic ranges of truth jets and egamma objects in different physics sample

  10. Jet rejection vs ETtruthJet DS5802 dijet (PTHard>15) ETclus>17 GeV DS5805 minbias (ETfiltr>6) ETclus>8 GeV DS5807 dijet (PTHard>35) ETclus>35 GeV DS5001 minbias (not filtr) ETclus>8 GeV DS5009 dijet (PTHard=8-17) ETclus>8 GeV DS5010 dijet (PTHard=17-35) ETclus>17 GeV DS5011 dijet (PTHard=35-70) ETclus>35 GeV DS5144 Z->ee ETclus>8 GeV • Clear seen threshold effects - compare di-jet data sample with PThard>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

  11. Jet rejection vs ETtruthJet DS5802 dijet (PTHard>15) ETclus>17 GeV DS5805 minbias (ETfiltr>6) ETclus>8 GeV DS5807 dijet (PTHard>35) ETclus>35 GeV DS5001 minbias (not filtr) ETclus>8 GeV DS5009 dijet (PTHard=8-17) ETclus>8 GeV DS5010 dijet (PTHard=17-35) ETclus>17 GeV DS5011 dijet (PTHard=35-70) ETclus>35 GeV DS5144 Z->ee ETclus>8 GeV No cut on Etclus

  12. Jet rejection vs ETcut DS5802 dijet (PTHard>15) DS5805 minbias (ETfiltr>6) DS5807 dijet (PTHard>35) DS5001 minbias (not filtr) DS5144 Z->ee

  13. Matching truth jets to original parton quite complex (and frequently impossible DS5001 Min bias DS5144 Z->ee

  14. b,c quark jets Only gluon jets light quark jets • Need to understand why min bias Rg/Rq ~ 3 and Z->ee Rg/Rq ~ 2 and

  15. Back up slides

  16. Jet rejection vs ETtruthJet

  17. Jet rejection vs ETtruthJet Etclus > 8 GeV

  18. Jet rejection vs ETClus

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