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b-Jet Energy Scale Determination Method for Top Mass

b-Jet Energy Scale Determination Method for Top Mass. Presentation for summer student program Mitsutoshi Ogino. Motivation. Systematic uncertainties of Mtop measurement by top mass template group. All-hadronic : ~45%. No missing objects. Many events come from All hadronic channel.

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b-Jet Energy Scale Determination Method for Top Mass

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  1. b-Jet Energy Scale Determination Method for Top Mass Presentation for summer student program Mitsutoshi Ogino

  2. Motivation Systematic uncertainties of Mtop measurement by top mass template group All-hadronic: ~45% No missing objects Many events come from All hadronic channel. But, there are large background … (I did not consider the background at this study) This is excellent prescription, but we always want confirmation from data. 1

  3. y perpendicular parallel x Method To estimate Jet Energy Scale Sum of energy is 0 on x-y plane fron Energy momentum conservation. To estimate Jet Energy Scale (JES), We watch response: 2

  4. Correction at All-hadronic (for check) Likelihood (including product templates) Estimation Top Mass estimation Method Identify b-quark with b-tagging and level 5 jet correction Match b-jet and 4 light quark jets. (dR < 0.4) Define as likelihood fitting function of b-jet energy scaling factor. Estimate mean and sigma from fitting function of likelihood. Check the effect of b-JES on parton, error bias and accuracy from plots. Estimate top-quark mass and effect of error. 3

  5. Event selection Lv:5_Correction (Pre-Selection) • Number of tight lepton = 0 • |Zjvert| < 60 cm • |Zjvert - Zpvert| < 5 cm • N(vert_class12) ≧ 1 • MET_significance < 3 • 6 ≦ Njet ≦ 8 (jets with Et ≧ 15, |η| ≦ 2.0) • DeltaRmin (dRmin) ≧ 0.5 between jets Matching 6 jets each other at dR < 0.4 after pre-selection. 4

  6. If… L(bJES) = “Gaussian” σbJES bJES 1 χ2=-2lnL σbJES L0+1 L0 bJES 1 Likelihood [Likelihood function] [The method of least squares (LS)] Estimate Mean, Mean’s Error, Sigma, and Sigma’s Error from χ2(bJES). Besides, to discuss accuracy … [pull] 5

  7. probability : Jet Energy Scale Signal template [response] Make signal templates and View the shift of response. After, search all fitting function at f=0.90~1.10 separating 21 variation. We fit the histograms above to get the P(xi,bJES). 6

  8. No of mean bJES Pseudo Experiment (practice) 1PE Example (f = 0.90) To estimate statistical uncertainties, We performed pseudo experiments. 1. Get 191 events from template histogram Nevt 2. Performed likelihood fit to get the bJES and its error. Repeat same procedure 10k times at each bJES bJES = 0.917 +/- 0.016 -2ln(L) fitting bJES 7

  9. Results (practice) 8

  10. We didn’t consider acceptance effect due to bJES Bad Fitting lead to slight bias & <1 pull width ⊿(bJES) ~ 0.017  ⊿(Mtop) = 1.2GeV We want to improve the uncertainties. Problem (for practice result) Try it again this analysis after introducing Top Specific Correction!! 9

  11. Matching Fitting Correct Jet Energy Top Specific Correction (TSC) Recipe for TSC in this study Change parameter form dR<0.4 to dR<0.1 Jet energy separate to 20~30, 30~40, 40~50, 50~60, 60~70, 70~100, and 100~ [Gev] each ranges. (to examine for Jet Energy dependence) Product distribution plots of JetEt – PartonEt at each ranges. Estimate mean and sigma around peak after fitting with Gaussian. Make templates from estimated value of mean and sigma 10

  12. Example (f = 0.90) probability response Making template (TSC) Make template probability of response about f=0.90~1.10 cases. original corrected To original response fit corrected… at f=0.90~1.10, corrected response approach 1-f, But no improve from original Cannot improve top mass using this Top Specific Correction… I abandoned to use this correcting method. 12

  13. Estimate Jet Energy Scale Result for practice Top Specific Correction Hereafter … summary To examine JES, We research response. ⊿(bJES) ~ 0.017  ⊿(Mtop) = 1.2GeV But, there are some problem. We do not have improvement from Top Specific Crrection. There is still scope for improvement. Try to improve using other correcting method? But, summer student program is last 2days only… 13

  14. Back up

  15. Template fitting（practice） Example (f = 0.90) 15

  16. Error result (for practice) Example (f = 0.90)

  17. Top specific correction（b-Jet） Number of event jetEt - partonEt 16

  18. Top specific correction (4 lq-Jet) Number of event jetEt - partonEt 17

  19. Template（TSC） response: f = 1.00 f = 1.10 probability response 18

  20. Top invariant mass(for practice)

  21. Mw constraint Nevt response

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