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Determination of Light Jet Energy Scale with Top Events Analysis

Extracting the light jet energy scale using top events analysis after the Rome workshop. Constraints, methods, and iterative techniques to determine the energy scale efficiently discussed. Results and systematics adjustments provided.

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Determination of Light Jet Energy Scale with Top Events Analysis

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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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