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Light jet energy scale determination with Top events After Rome Workshop status

Light jet energy scale determination with Top events After Rome Workshop status. D. PALLIN 15/12/05. Rome Workshop. Extract the light jet energy scale E parton -> E jet MC -> E jet recons no hypothesis on calib funtion jets > 40 GeV ; W sample from top sample 85%purity .

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Light jet energy scale determination with Top events After Rome Workshop status

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  1. Light jet energy scale determination with Top eventsAfter Rome Workshop status D. PALLIN 15/12/05

  2. Rome Workshop • Extract the light jet energy scale E parton -> E jet MC -> E jet recons • no hypothesis on calib funtion • jets > 40 GeV ; W sample from top sample 85%purity Calibration function  (Ejet) = Eparton / Ejet AOD Cone 04 EPart / E An example: Rome AOD  (Ejet) = 1. to 1.1 ‘cone 04’ E D. Pallin TOP meeting DEc 2005

  3. Rome Workshop Ingredients • Constraint 1 • Rq: angle well reproduced if jet masses used • Constraint 2 : 1 and 2 have the same dependance in function of E ( f(E) ) give the correlation between all W mass reconstructed => Build MW distributions in function of E to keep correlation each MW distrib gives <MW> (E) <MW> (E) depends on calib MW E D. Pallin TOP meeting DEc 2005

  4. Rome Workshop Methods • Use MW distributions in function of E • Find best 1 and 2 such that <MW> (E) = MWPDG(E) • => 1/ 2 FIT <MW> (E) = MWPDG(E) • => 2/ iterative method without fit D. Pallin TOP meeting DEc 2005

  5. R E Iterative Method to extract the E scale • Constraint R=1 • compute R for k bins in E • apply kfactors on R and recompute R n times => AOD W Recons. No comb BKG D. Pallin TOP meeting DEc 2005

  6. Iterative Method to extract the E scale • compute R for k bins in E • apply kfactors on MW and recompute R n times => EPart / E EPart / E E E D. Pallin TOP meeting DEc 2005

  7. Method1 Results after recalibration AOD 4000 W Recons. No comb BKG • Function found with any ‘a priori’ hypothesis before EPart / E Mw E after D. Pallin TOP meeting DEc 2005

  8. After Rome Workshop • Reduce known systematics • Try to get calibration below 40 GeV • try to explain the connections existing between the know systematics on calibration method and the observed Mtop dependence in function of Pt D. Pallin TOP meeting DEc 2005

  9. Systematic 1 • E_jet / E_part % E_parton MC calib=1 D. Pallin TOP meeting DEc 2005

  10. Systematic 1 • E_jet / E_part % E_jet MC calib=1 • !! No more calibrated ??? • Bias is within 1% above 40 GeV • But need to be corrected • huge effect below 40 GeV D. Pallin TOP meeting DEc 2005

  11. E_jet j E_part i-1 i+1 i Systematic 1 • Why ? Ej=ai Epi overestimated (E/Ep)j = Ej / (ai Epi) underestimated D. Pallin TOP meeting DEc 2005

  12. Systematic 1 • How to correct? origine of bias : purely statistical from : E shape+ E resolution negligeable if resolution(E)<<E important when resolution(E)~E Need to know shape and resolution • Use full Top MC to extract bias • Compute statistical function = corr_det D. Pallin TOP meeting DEc 2005

  13. Systematic 1 • E_part / E_jet % E_jet after bias correction • E_jet =E_jet X corr_det Corr_det Works for any generated resolution and E shape Shape taken as the observed E shape D. Pallin TOP meeting DEc 2005

  14. Effects on Mw • MWREC-cor = MWREC X sqrt(corr_det (E1) ) • BUT additionnal effect (effect 2) • Mw MC calib=1 Mw=79.93 ±0.08 GeV ; 470 MeV from the generated W mass D. Pallin TOP meeting DEc 2005

  15. Effects on Mw (effet 2) • Mw MC calib=1 • 1+r1+r2 almost gaussian, centered on 1 • r1r2 not linear, introduce a bias • effect seen in SM group (Z resonnance) and computed recently by Kramner. Same as our result • depends on E • Alreaydy known effect but negligeable (0.5%) for our purpose D. Pallin TOP meeting DEc 2005

  16. Effects on Mw (effect 1) • Mw % E_parton MC calib=1 D. Pallin TOP meeting DEc 2005

  17. Effects on Mw (systematic 1) • Same effect as on • Ejet/Epart • Same correction apply • MWrecx corr-det is flat in function of E => Same type of correction apply to correct MW in function of Pt cut • Mw % E MC calib=1 • Meth1 on AOD: Calibration obtained is a convolution of calib X corr_det MW%Ejet , Ejet/Ep%Ejet distrib are flat MW%Ep , Ejet/Ep%Ep distrib no more flat MW Ejet EPart / E D. Pallin TOP meeting DEc 2005 Ejet

  18. Method 1 remove systematics • Energy resolution and distribution needed • Good estimate of the shape given by Ejet shape • E Resolution could be given by MW resolution OR/AND from outside ( Z+jets) • Suppose resolution and shape known : • Correct bias with fonction corr-det • Apply method1 as previously • result OK for E>40GeV • Correlation found between calib and corr-det below 40GeV. D. Pallin TOP meeting DEc 2005

  19. E resolution f rom MW width • MW /MW do not depend on calib • use MW distributions for different Energy bins • => Measure MW /MW in function of E • Extract E/E from the constraint : • result is enough precise to be used in coor_det D. Pallin TOP meeting DEc 2005

  20. Conclusion for calib • to calibrate jets below 40 GeV, knowledge of E and E distributions are needed • Still possible to extract jet energy scale without using MC or calib function hypothesis • OR use MC • apply E and calibration on partons • find the best E and calibration reproducing the observed MW %E and E distribution. D. Pallin TOP meeting DEc 2005

  21. Mw and Mtop in function of pt cut • for the same reasons (effets from E and E distributions) • Mw or Mtop % Pt cut are flat . No dependence • Mw or Mtop % Ptjet cut are no flat. Huge effect on Mtop • Easy to handle for MW. Tricky for Mtop • Mtop : use MC to get the Mtop value for a given Ecut • use measurement of E and calibration from MW for light jets • find the best E and calibration for bjets reproducing the observed Mtop %ptcut and ptb distributions. This D. Pallin TOP meeting DEc 2005

  22. Mw and Mtop in function of pt cut • for the same reasons (effets from E and E distributions) • Mw or Mtop % Pt cut are flat . No dependence • Mw or Mtop % Ptjet cut are no flat. Huge effect on Mtop • Easy to handle for MW. Tricky for Mtop • Mtop : use MC to get the Mtop value for a given Ecut • To be tested • use measurement of E and calibration from MW for light jets • find the best E and calibration for bjets reproducing the observed Mtop %ptcut and ptb distributions. • How sensible is the dependence to the b jet calib. Could we calib also b jets form the Top ? D. Pallin TOP meeting DEc 2005

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