Reconstruction of Pi0 at low pT from towers only

ALGO
  • cuts and params:
     float  samplFrac=40.; // MC=0.04, realADC=40;
  float  highEnergy=.2;
  float  zLimit=.7;
  float  isoLimit=.90;
  float  mPi0=.135;//.547; 
  opening Angle limit (opAng)
  int mixFlag=1;
  • cluster finder:
    - tower energy eH=GeantEnergy/samplFrac (or realADC/samplFrac)
    - find high towers with eH>highEnergy
    - sum cluster energy (eC) over 3x3 patch of towers arround HT
    - separation :must be at least one low energy tower between any HTs
    - * isolation: eH/eC > isoLimit

  • pi0 finder:
    - accept only events with exact two clusters
    - reject (too) asymmetric decay : |eC1-eC1|/sum <zLimt
    - * opening angle cut: [0.2,0.3] rad

  • optional event mixing if mixFlag=1;

    One pi0 per event was thrown at eta=1.6 and phi =-90 deg and processed by GSTAR. Geant energy deposit in GeV is plotted for all 240 towers.

    Reco of one meson/evet without isoLimit and angLimit, 1000 events each time
    pi0 with pT=1 GeV
    pi0 with pT=1.5 GeV
    Eta with pT=2 GeV
    Reco of PYTHIA minb evets, 50 K events with isoLimit and angLimit
    Reco of PYTHIA minb evets, 50 K events with isoLimit and angLimit and mixed events
    Normal events vs. mixed events, invariant mass: