Comparison of Pi0's reconstructed
with SF=60 ch/GeV (best pi0 invM) and 50ch/GeV (from MIP calib)
> What do you get for the reconstructed p_T for these > two triggers if instead you use gains determined from > the MIP calibrations, assuming 5.0% sampling fraction? Prescription of converting the MIP peak to absolute energy calibration for tower Assumptions and definitions: * tower consist of 24 scint layers 4 mm each, total depth D=9.6cm ( the 3 pre/post shower layers have 5 mm, but the light collection efficiency is lower) * energy loss for MIP in scint is 1.8 MeV/cm ( in the minimum of ionization, scint=carbon with density of 1g/cm3) * relative gain of i-th tower is denoted g_i * scale factor (SF) is overall energy calibration for EM energy * sampling fraction for electromagnetic energy SamplFrac=0.05 The peak value of MIP ADC (total energy) is given by: Emip(ch)= dE/dX * D /tanh(eta)* g_i * SF(ch/GeV)/SampFrac The reconstructed EM energy: Eem(GeV) = ADC/g_i /SF This definition is little awkward, but the EM sampling fraction is hidden in SF for reconstruction of EM energy. Note, I'm not taking about transverse energy at any moment, the total energy is meant at all places. If all of the above makes sens, then for the tower 5TB09 the values are MIP peak at ADC=19.8 g_i=1 per definition eta=1.3 for the etaBin=9 SF = Emip * tanh(eta) * SamplFrac / ( dE/Dx * D * g_i) SF = 19.8 * 0.86 *0.05 /(0.0018 *9.6 ) = 49.3 ch/GeV This is just 20% below the value needed to get the pi0 peak & invM at the right place.
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, relative gains from MIPs (for eta bin 1-4) & slopes (1-4).
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
SF=50 ch/GeV;    trig=1151+2+4   
Npeak= 2492 ;
    invM fit=0.173 +/- 0.002 GeV;   
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SF=60 ch/GeV;    trig=1151+2+4   
Npeak= 1905 ;
    invM fit=0.157 +/- 0.002 GeV;   
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