-- ChengguangZhu - 10 Feb 2009


  • exercise with Zee sample, to measure the cut-based electron PID efficiency over reconstructed electrons, electron charge confusing rate, electron to gamma fake rate and more
  • use fdr08_run2.0052300.physics_Egamma.merge.AOD.o3_f48_m27, with backgroud included


method to fill ntuple

  • first of all, event should belong to some trigger stream:
    • tag the event with the trigger name by fill ntuple.
  • basic selections on electrons:
    • pt>15GeV, abs(eta)<2.5
    • out of barrel/endcap transition region (1.37<abs(eta)<1.52)
  • compose z candidate with any combination of 2 objects of electron, gamma ...
    • the 2 object should have deltaPhi>3/4PI, means in opposite hemisphiere.
  • ntuple filled.
    • pair mass
    • number of pair per event
    • Pdg_Id1, (int)selection criteria1, author1, EoverP1
    • Pdg_Id2, (int)selection criteria2, author2, EoverP2

method of measurement once ntuple filled

  • cut-based PID efficiency over reconstruction&trigger efficiency using tag and probe method.
    • plot pair mass with pdg_id1=11/-11, selection criteria1 is tight and pdg_id2=-11/11,
    • fit around the Z mass peak using a Gaussian distribution convoluted with a Breit-Wigner plus an exponential function and calculate the number of signal z->e+e- events Nete inside z mass window (80GeV to 100GeV)
    • plot again adding selection criteria2 as loose, medium, tight.
    • fit and caculate numbers of signals Netel, Netem, Netet
    • the PID efficiency over reco/trigger efficiency is as Netel/Nete, Netem/Nete, Netet/Nete for loose, medium and tight selection.

The results are here, plot in following

Nete = 146.184
Netel = 135.248
Netem = 113.601
Netet = 92.1313
 the electron loose cut efficiency w.r.t. basic reconstruction and cut is 92.5194%
 the electron Medium cut efficiency w.r.t. basic reconstruction and cut is 77.7109%
 the electron tight cut efficiency w.r.t. basic reconstruction and cut is 63.0243%

  • electron charge confusion rate.
    • plot mass pair with pdg_id are both 11 or -11, with selecttion cretiria both are tight
    • fit and calculate the signal number Netet_sc (sc = same charge)
    • the confusiong rate is Netet_sc/(Netet_sc+Netet) with tight selection.

  • election to gamma fake rate:
    • same as above, calcualte the signal of Netgt and fake rate is Netgt/(Netet*2+Netgt*2), ignore Netet_sc

The results are here left (e+- and e+-) middle(e+- and gamma) right (gamma and gamma) : need more statistics for left and right

Netgt = 12.275
  the fake rate of e->gamma with tight selection is 12.275/(92.1313*2+12.275*2)=5.8%

  • chargeconfusionandfakerate.gif:


Topic attachments
I Attachment History Action Size Date Who Comment
Unknown file formatcxx AnalysisSkeleton.cxx r1 manage 45.9 K 2009-02-18 - 01:29 ChengguangZhu  
Header fileh AnalysisSkeleton.h r1 manage 6.9 K 2009-02-18 - 01:29 ChengguangZhu  
Header fileh ConsParameters.h r1 manage 2.5 K 2009-03-16 - 09:01 ChengguangZhu  
Header fileh DrawTools.h r1 manage 10.5 K 2009-02-18 - 01:20 ChengguangZhu  
Header fileh HistTools.h r1 manage 5.2 K 2009-02-18 - 01:21 ChengguangZhu  
GIFgif PID_efficiency.gif r2 r1 manage 26.2 K 2009-02-13 - 06:30 ChengguangZhu  
GIFgif chargeconfusionandfakerate.gif r3 r2 r1 manage 16.1 K 2009-02-18 - 01:09 ChengguangZhu  
Unknown file formatcxx pid_check.cxx r2 r1 manage 14.7 K 2009-03-16 - 09:00 ChengguangZhu  
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Topic revision: r7 - 2009-03-16 - ChengguangZhu
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