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Electron Identification

Electron Identification. Supriya Das Gesellschaft für Schwerionenforschung mbH (GSI). Till the last collaboration meeting we had the concept and results from electron identification. But, the software was standalone i.e. one code for electron identification and pair analysis.

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Electron Identification

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  1. Electron Identification Supriya Das Gesellschaft für Schwerionenforschung mbH (GSI)

  2. Till the last collaboration meeting we had the concept and results from electron identification. But, the software was standalone i.e. one code for electron identification and pair analysis. Requirement of self sufficient software to provide identified electrons to be used in further analysis, mixed event generation etc. Needs to be flexible/user friendly in terms of changing cuts for different detectors, decision of using different cuts for identification ability to select electrons identified by one or more detectors Requirement to disentangle the real and MC world. Motivation Supriya Das, CBM Collaboration meeting, Dresden

  3. Task : CbmDileptonAssignPid Input : All arrays from reconstucted data (no MC) Output : 1. Collection of identified tracks (CbmDileptonTrackReal) Global track index, chi2primary, momentum, isRich, isTrd, isTof 2. Histograms before and after cuts Constructor contains all default cut values and switches User has to provide user defined values in macro (see later) [ no cut on chi2primary, can be used for secondary electron analyses] Software Task : CbmDileptonAssignMCid Input : All reco and mc arrays Output : 1. Collection of tracks after MC association (CbmDileptonTrackSim) momentum, fakeTrack, fakeRing, MCPdg, MCMotherId, MCMotherPdg 2. Histograms for efficiency, purity, pion,suppression etc. This collection has one-to-one correspondence with previous one [ two parameters needed to be supplied, cut on chi – to select primary radial distance – to define RICH acceptance] Supriya Das, CBM Collaboration meeting, Dresden

  4. Simulation MC information Reconstructed event CbmDileptonAssignMCid CbmDileptonAssignPid CbmDileptonTrackSim CbmDileptonTrackReal Block diagram of electron id Real Supriya Das, CBM Collaboration meeting, Dresden

  5. CbmDileptonAssignPid – flow chart isTRD isTOF Supriya Das, CBM Collaboration meeting, Dresden

  6. RichPid – flow chart Supriya Das, CBM Collaboration meeting, Dresden

  7. gSystemLoad->(“libDilepton”); // Electron id assignment CbmDileptonAssignPid* taskPid = new CbmDileptonAssignPid(1); Float_t aRichCuts[] = {1., 0.4, 0., 130, 21.85, 4.35, 6.17, 0.14}; // Distance, SelectionNN, selection2D, Radial, NHitMean, NHitSigma, RMean, RSigma taskPid->SetRichCuts(true, true, aRichCuts); //sMomentum, sSelection (true=NN, false=2D) Float_t aTrdCuts[] = {1.5,0.95, 1.1, 21., 0.9}; // Mom, PidLikeLow, PidLikeHigh, PidWkn, PidAnn taskPid->SetTrdCuts(true,true,false,false,aTrdCuts); //sLike, sWkn, sAnn taskPid->SetTofCuts(true,0.01); //sMomentum, Mass2 fRun->AddTask(taskPid); // MC Association, needed for simulated data stream CbmDileptonAssignMCid* taskMCid = new CbmDileptonAssignMCid(); fRun->AddTask(taskMCid); Software (contd.) Macro to run the electron id … Supriya Das, CBM Collaboration meeting, Dresden

  8. 5 e- and 5 e+ embedded into central UrQMD events for three different beam energies Standard and low mass dilepton* set up used 10,000 events simulated Standard cuts used for identification ANN and Wkn methods for TRD are used – Likelihood needs tuning Software used from aug07 release Systematics Efficiency = identified true electrons / accepted electrons Pion suppression = pions identified as electrons / accepted pions * thin target, extended MVD and STS, 70% magnetic field Supriya Das, CBM Collaboration meeting, Dresden

  9. Identification by TOF Identification criteria Identification by RICH • Identification by TRD based on statistical • analyses of total energy loss: • ANN - e > 0.8 • Wkn - e > 11 • Likelihood – 0.95 < e < 1.1 (any one or combination could be used) Supriya Das, CBM Collaboration meeting, Dresden

  10. Impurities in identified electrons Particles/event • All : 5.81 • True e : 5.35 • Fake : 0.09 • : 0.06 p : 0.014 Others : 0.02 Au+Au @ 25 AGeV Standard set up Combined information of RICH+TRD+TOF Supriya Das, CBM Collaboration meeting, Dresden

  11. Falsely matched pions Au+Au @ 25 AGeV Standard set up Electron ring falsely matched with a nearby pion track Supriya Das, CBM Collaboration meeting, Dresden

  12. True p Falsely matched p Pions mis-id as electrons Au+Au @ 25 AGeV Standard set up Supriya Das, CBM Collaboration meeting, Dresden

  13. Efficiency of electron identification Low mass dilepton set up Standard set up 25 AGeV Supriya Das, CBM Collaboration meeting, Dresden

  14. Pion suppression Low mass dilepton set up Standard set up 25 AGeV Supriya Das, CBM Collaboration meeting, Dresden

  15. Efficiency Low mass dilepton set up Standard set up 35 AGeV Supriya Das, CBM Collaboration meeting, Dresden

  16. Pion suppression Low mass dilepton set up Standard set up 35 AGeV Supriya Das, CBM Collaboration meeting, Dresden

  17. Efficiency Low mass dilepton set up Standard set up 15 AGeV Supriya Das, CBM Collaboration meeting, Dresden

  18. Pion suppression Low mass dilepton set up Standard set up 15 AGeV Supriya Das, CBM Collaboration meeting, Dresden

  19. Efficiency - energy dependence Efficiency from RICH only Standard set up Low mass dilepton set up Variation of efficiency with energy < 10 % Supriya Das, CBM Collaboration meeting, Dresden

  20. Energy dependence (contd.) Standard set up Low mass dilepton set up Variation of efficiency with energy < 10 % Supriya Das, CBM Collaboration meeting, Dresden

  21. p-suppression – energy dependence Standard set up Low mass dilepton set up Supriya Das, CBM Collaboration meeting, Dresden

  22. Comparison between two TRD methods • The cuts need to be optimized to get the best efficiency/ pion suppression factor • Likelihood method needs more tuning Supriya Das, CBM Collaboration meeting, Dresden

  23. New, user friendly software for electron identification for di-electron analyses is in place. Results from systematic study of this package have been presented Different set ups (standard, low mass dileptons) Different energies Different methods for TRD identification Cuts could further be optimized to obtain the best efficiency and pion suppression. Study of identification with the compact RICH to be done. Summary and Outlook Supriya Das, CBM Collaboration meeting, Dresden

  24. All cuts/switches can be modified from macro – user friendly. The collections could be kept in root memory and accessed by the next task / could be stored in an intermediate file for later use (self sufficient, has all information). Caveat : Can not provide cut-by-cut efficiencies possible solution : go to subtask level All codes are in svn (in the last release) Tasks and other classes in cbmroot/dilepton Macro in cbmroot/macro/dilepton Documentation exists in Wiki page, http://cbm-wiki.gsi.de/cgi-bin/view/CbmRoot/CbmReconstruction/#Electron_Identification CBM-Note in preparation. Summary & outlook (contd.) Supriya Das, CBM Collaboration meeting, Dresden

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