Comparison of Pi0's reconstructed from events triggered with MinB and E-HT trigger

The events taken with ppTrans-1 trigger were sorted according to the trigger: 1000=MinB, 1152= EHT2, 1150=1151+1152+1154=EHT1&2(fast+slow).
The params for pi0 reconstruction: seed energy of 0.6 GeV, seed/total energy >0.7, pi0 inv mass cut=0.07-0.22 GeV, scale factor 60 ch/GeV, relative gains from MIPs (for eta bin 1-4) & slopes (1-4).

The cluster finder has been improved: energy of towers between the clusters seed is divided proportionally to the seeds energies (before it was just 1/2 or 1/3).

Properties of reconstructed pi0 change with the trigger:
- pi0 energy ~2 GeV, ~5 GeV, ~7.5 GeV (for 1000, ~1151+4, 1152)
- pT <1 GeV, ~1.5 GeV, ~2.5 GeV
- Z-shape is flat and truncated for the minB trigger. Z<0.2 means Egamma<0.6*2 GeV=1.2 GeV, what is equivalent for the other Egamma>0.8 GeV. Note, the seed cut in algo is very close at 0.6-0.8 GeV.
- Z-shape for HT data is triangular, peaked at Z=0.65 and 0.75 meaning very asymmetric pi0 decays were detected (with energy spilt of 1:4 and 1:7). This is reasonable, because for a symmetric decay of 5-7 GeV pi0 both gammas would hit the same tower and are unreconstructable without SMD.
- pi0 inv mass increases for HT trigger data, since the cluster energy reconstruction reach its limitation for a very asymmetric energy shearing.
For small angles : invM=sqrt(E1*E2)*theta12
The smaller energy has the larger relative error (always up, due to the energy leak) and dominates the error of invM. Similar feature is reproduce in M-C.

Compare the plots below with the M-C simulation posted at the simulation page

Six panels below show:
-top left: invariant mass spectrum for all events,
-top mid: energy of pi0, after invM cut =0.05,0.22 GeV
-top right: transverse momentum of pi0, after invM cut
-bottom left: energy shearing Z=|E1-E2|/(E1+E2) of 2 gammas, after invM cut
-bottom mid: opening angle of 2 gammas, after invM cut
-bottom right: pseudo-rapidity distrib. of pi0, after invM cut
Green histos represent mixed events

Runs used: R4123094, R4123097, R4123098, R4123099, R4123132, R4123133, R4124003, R4124008, R4124013, R4130010

Real Data MinB trig=1000 Npeak= 466 ; Npi0=140 + / - 28 ; invM fit 0.135 +/- 0.005 GeV; all.ps , invMcut.ps

Real Data HT trig=1151+2+4, EHT1 dominates   Npeak= 24576 ; Npi0=11129 + / - 195 invM fit 0.157 +/- 0.001 GeV all.ps , invMcut.ps

Real Data EHT2 trig=1152 Npeak= 2118 ; Npi0=789 + / - 59 ; invM fit 0.173 +/- 0.003 GeV; all.ps , invMcut.ps