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Etmiss Reconstruction and Calibration in Athena

Etmiss Reconstruction and Calibration in Athena Workshop on Energy Calibration of the ATLAS calorimeters July 23, 2002. Reconstruction & Calibration Starting point :

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Etmiss Reconstruction and Calibration in Athena

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  1. Etmiss Reconstruction and Calibration in Athena Workshop on Energy Calibration of the ATLAS calorimeters July 23, 2002 D.Cavalli, S. Resconi

  2. Reconstruction & Calibration • Starting point :  Etmiss reconstruction from all calorimeter cells  Comparison of reconstructed Etmiss quantities per calorimeter and total betweenAthena and Atrecon • To have an Etmiss value “usable” for physics studies :  Calibration Contribution of muons and eventually not full-simulated calorimeter regions • To evaluate Etmiss resolution :  MC truth Etmiss Calculation of SumEt:  ( Etmiss)  SumEt • Calibration :  Region Calibration , H1-Style Calibration  Comparison with the refined calibration method applied in ATLAS Physics Technical Design Report, TDR Calibration D.Cavalli, S. Resconi

  3. Etmiss reconstruction from calorimeters : Ex(y)miss_calo = - Ex(y) performed on calo cells Next slide : • Comparison of not calibrated Etmiss_calo between Athena and Atrecon :  On a sample of TDR full simulated data (98_2): bbA   - had m(A )=150 GeV , 665 evts  full simulation within || < 3  read withAtrecon: release 1.3.0(atrecon-01-42-29)  andAthena: release 3.1.0, used RecExample + new MissingET package(now in current release )  No energy threshold applied (no noise added yet !!) D.Cavalli, S. Resconi

  4. Athena - Atrecon superimposed (!!) distributions of ETmiss in calos 1 2 EM Barrel PS Barrel 3 4 Tile EM EndCap 5 7 D.Cavalli, S. Resconi HEC PS EndCap(only Athena histo)

  5. Forward Calorimeter (Calo 6) has not been full simulated in this event sample • Perfect agreement of Etmiss_calo reconstruction in Calorimeters between Athena and Atrecon (!!) • PS EndCap contribution not included in Atrecon Etmiss routine (EMISREC) , so the total not calibrated reconstructed Etmiss is slightly different between Athena and Atrecon Athena Atrecon < > ~ 46.9 < > ~ 47.3 Total Etmiss ||<3 D.Cavalli, S. Resconi Total Etmiss ||<3

  6. Contributions implemented in the Athena MissingET package : To obtain an Etmiss value “usable” for physics analysis (1) Calibration : a first rough method= Region Calibration • 7 calibration constants : ( MissingETRegionCalib class) are applied to the partial contributions from the calorimeters: Ex(y)miss_reg_calib += const( 17 )  Ex(y)miss_calo ( 17 ) Etmiss_reg_calib = sqrt (Exmiss_calib  2 + Eymiss_calib  2) have been obtained minimizing Etmiss resolutionof bbA  • new calibrated quantitiesadded to output CBNT • possibility tochange default calibration constants in the JobOptions D.Cavalli, S. Resconi

  7. Athena < > ~ 47.3  ~ 9 - - - =TRUTH Etmiss Etmiss before calib ||<3 Etmiss Resol. before calib ||<3 < > ~ 57  ~ 5.4 in CBNT D.Cavalli, S. Resconi Etmiss after calib ||<3 Etmiss Resol. after calib ||<3

  8. Etmiss Resolution||<3= = ( Ex(y)miss Rec ||<3 - Ex(y)miss Truth ||<3) Ex(y)miss Truth= -  px(y) of stable parts except neutrinos and ’s (2) Contribution of not full-simulated calorimeter regions :  when the full simulation is not performed till || = 5 accessing MC truth info (3) Muon contribution : accessing MC truth info(will substituted by reconstructed muons when available in Athena) (4) MC truth Etmiss :  to calculate directly from CBNT the Etmiss resolution (5) Calculation of SumEt = ETcalo cellswithin ||< 5 and Calibration: SumEt_reg_calib += const( 17 )  SumEt_calo ( 17 ) To evaluate Etmiss resolution  ( Etmiss )  SumEt D.Cavalli, S. Resconi

  9. All Etmiss MC truth quantities calculated in CBNT_MissingETtruth class in Athena MissingEt package : • a separate CBNT algorithmfor Etmiss MC truth quantities from the reconstructed ones • calculation of :  “true” Etmiss : from neutrinos (no  cut)  Etmiss seen in calorimeters : from stable particles in calos (= no neutrinos , no  ` s) for 2 -ranges : with |-range| <etafullsim  withetafullsim < |-range| < 5 etafullsim parameter = -range of full simulation, set by the user in the JobOptions  truth muon contribution : from "measurable" muons with pt > 6 GeV and ||< = 2.5 D.Cavalli, S. Resconi not yet in release

  10. Etmiss quantities to be used in physics analysis < > ~ 24.4 < > ~ 25.3 in CBNT Etmiss to be used for physics Etmiss Truth(from neutrinos) Etmiss Calib + forward (p.l.) +  (p.l.) < > ~ 185  ~ 6.8 Sumet to be used for physics SumET Calib + forward (p.l.) Final Etmiss Resolution D.Cavalli, S. Resconi

  11. final Etmiss Resolution= = ( Ex(y)miss Rec ||< 5 - Ex(y)miss Truth (no  cut) ) takes into account also detector coverage • comparing with the results published in the TDR, that have been obtained with a more refined calibration method: (1) TDR Calibration • a slightly worse resolution has been obtained with this first rough calibration method implemented in Athena: (2) Region Calibration • some promising results with an other calibration approach implemented in Athena : (3) H1-Style calibration • comparison between those different approacheson a wider statistic (preliminary results !!) More in details D.Cavalli, S. Resconi

  12. (1) TDR Calibration : • Results published in the ATLAS Physics Technical Design Report (TDR) have been obtained using different set of calibration constantsfor hadronic cluster cells, em cluster cells and cells outside clustersin each calorimeter region • This means to:  start from the identified objects (jets, e/ clusters, tau jets), and calibrate all associated cells ,  calibrate cells outside clusters (using minimum bias events)  sum all contributions at cell level to calculate final Etmiss…. If the identified objects are already correctly calibrated, in principle, the final Etmiss is automatically calibrated too, only cells outside clusters contribution should be corrected … • This refined calibration method can be applied only after cluster identification and calibration…more work needed to implement all that in Athena D.Cavalli, S. Resconi

  13. Published in ATLAS physics TDR - 1999 Etmiss Resolution = 0.46  SumEt bbA  evts Noise added Ecell > 1.5 (Noise) Etmiss Resolution =  ( Ex(y)miss Rec||< 5 - Ex(y)miss Truth(no  cut) ) SumEt = ETcalo cellswithin ||< 5 D.Cavalli, S. Resconi

  14. (2) Region Calibration in Athena: • is an approximation of the complete Etmiss calibration: the present constants are average constants for cells in em clusters, hadronic clusters and outside clusters • calibration constants depend on physics event type and energy (!!) :3 sets of calibration constants have been provided for low, middle and high range of A masses • users can calculate calibration constants for their own physics events using Etmiss truth quantities from CBNT • This is a rough calibration method that has been implemented in Athena as first step to provide soon a “usable Etmiss” for physics D.Cavalli, S. Resconi

  15. (3) H1-Style Calibration in Athena: • First attempt to calibrate Etmiss with H1-Style calibration method in Athena • Simple approach :  used available weights tuned for jets (see next slide): • New calibration class in MissingET package (MissingETH1Calib class ) :  apply H1 weights to all calorimeters cellsentering in the Etmiss calculation 4 new calibrated quantities in output CBNT : Ex(y)miss_H1_calib, Etmiss_H1_calib, SumEt_H1_calib not yet in release D.Cavalli, S. Resconi

  16. (3)H1-Style Calibration in Athena: • H1 weights :  from Table 1 of note “H1-Style Jet Calibration in Athena” , by H. Ma, F.E. Paige, S. Rajagopalan ( 3 May 2002 ): tuned for jets (JET35 sample, TDR geometry) depend on cell energy and Calorimeter region   dependency is not yet taken into account, as first approximation  for the moment hardwired in the code (still to think how to make them accessible from the jobOptions) • Comparison between Etmiss Region Calibration and Etmiss H1-Style Calibration on 2 mass points : m(A )=150, 800 GeV  preliminary results... D.Cavalli, S. Resconi

  17. m(A)=150 GeV Etmiss: <REG/truth> = = 0.997 < > ~ 57  ~ 5.4 - - - =TRUTH Etmiss Etmiss after REG calib ||<3 Etmiss Resol. After REG calib ||<3 < > ~ 55.5  ~ 4.5 Etmiss: <H1/truth> = = 0.965 D.Cavalli, S. Resconi Etmiss after H1 calib ||<3 Etmiss Resol. After H1 calib ||<3

  18. m(A)=800 GeV Etmiss: <REG/truth> = = 1.040 < > ~103.2  ~13.2 - - - =TRUTH Etmiss Etmiss after REG calib ||<3 Etmiss Resol. after REG calib ||<3 < > ~99.72  ~11.4 Etmiss: <H1/truth> = = 1.004 D.Cavalli, S. Resconi Etmiss after H1 calib ||<3 Etmiss Resol. after H1 calib ||<3

  19. Preliminary comparison of these 2 new implemented calibration methods in Athena with Atlas physics TDR resultson a wider statistic • Event samples : physics channels: bbA   - had, bbA  had - had  A mass points : m(A )=150, 300, 450, 600, 800 GeV  total number of evts : ~ 5650 TDR full simulated data (98_2) within || < 3, read with Athena: release 3.2.0, used RecExample + new MissingET package D.Cavalli, S. Resconi

  20. REGION + TDR calibration H1-Style + TDR calibration No Noise addition in Athena results (not yet available) !! Etmiss Resolution =  ( Ex(y)miss Rec||< 5 - Ex(y)miss Truth(no  cut) ) SumEt = ETcalo cellswithin ||< 5 preliminary !! D.Cavalli, S. Resconi

  21. Last Minute Results... H1-Style H1-Style H1-Style + TDR calibration Added an event sample with  edecays : physics channels: bbA  e - had  total number of evts : ~ 2500 (low statistic) Red curve =all decay channels weighted with the right decay BR: BR(bbA  e - X) ~30 % D.Cavalli, S. Resconi

  22. Conclusions : H1-Style + TDR calibration H1-Style Calibration seems a very powerful and promising method to calibrate Etmiss : • Etmiss resolution “seems “ in nice agreement with TDR results (but...no noise added !) • Etmiss mean value in agreement with the Truth mean value within few % • H1-Style Calibrationresults to be refined : on more statistic  with noise addition (when it will be available in Athena) : expected a worsening of the results (!!)  re-tuning H1 weights (?) TDR Calibration to be implemented ... WORK IN PROGRESS... D.Cavalli, S. Resconi

  23. From talk by Srini, ATLAS Software Week, May 30 2002 D.Cavalli, S. Resconi

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