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Background determination in early data for single electron trigger

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:

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Background determination in early data for single electron trigger

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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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