# 2009.11.10 BEMC sampling fraction and clustering

Monte-Carlo setup:

- Throwing one photon per event
**Full y2009 STAR geometry**configurations with and without LOW_EM option.

Note: LOW_EM cuts are listed at the bottom of this page,

and some related discussion can be found in this phana thread- Throw particles flat in eta (-0.95,0.05) amd (0.05, 0.95), phi (0, 2pi), and energy (30 +/- 0.5 GeV)
- bfc.C options:

trs,fss,y2009,Idst,IAna,l0,tpcI,fcf,ftpc,Tree,logger,ITTF,Sti,MakeEvent,McEvent,

geant,evout,IdTruth,tags,bbcSim,tofsim,emcY2,EEfs,

GeantOut,big,-dstout,fzin,-MiniMcMk,beamLine,clearmem,eemcDB,VFPPVnoCTB - Use
**fixed (7%) sampling fraction in StEmcSimpleSimulator.cxx**

mSF[0] = 1/0.07;

mSF[1] = 0.;

mSF[2] = 0.; - Vertex z=0
- 50K/per particle type

Geometry configurations and notations:

**BEMC-noLOW_EM**: Full STAR y2009 without LOW_EM option**BEMC-LOW_EM**: Full STAR y2009 with LOW_EM option

data base settings (same settings in bfc.C (Jan's trick) and in my MuDst reader):

dbMk->SetFlavor("sim","bemcPed");

dbMk->SetFlavor("Wbose","bemcCalib");

dbMk->SetFlavor("sim","bemcGain");

dbMk->SetFlavor("sim","bemcStatus");

Note: for BEMC ideal pedSigma set to 0, so effectively

there is no effect when I apply 3-sigma threshold above pedestal.

**Figure 1:** Sampling fraction (0.07*E_reco/E_thrown) distribution: average vs. gaussian fit

E_reco is the total energy in the BEMC towers from mMuDstMaker->muDst()->muEmcCollection()

E_thrown energy of the thrown photon from tne GEant record

**The difference between fit and using average values is < 0.7%**

**Figure 2:** Otliers vs. eta and phi: (left) no energy reconstrycted, (right) s.f. < 55%

Most outlier are at eta = 0, -1, +1

**Figure 3:** Sampling fraction (0.07*E_reco/E_thrown) distribution

Effect of LOW_EM cuts

**Figure 4:** Sampling fraction vs. thrown photon eta (left) and phi (right)

Average is taken over a slice in eta or phi with cut on outliers (events with s.f. < 5.5% rejected)

**Figure 5:** Sampling fraction vs. thrown position (eta and phi)

Average is taken over a slice in eta or phi with cut on outliers (events with s.f. < 5.5% rejected)

**Figure 6:** (left) Single tower sampling fraction

and (right) energy ratio of 1x1 cluster to the total BEMC energy

Not much of the effect from LOW_EM cuts on the 1x1 clustering. Need to look at other (2x1, 2x2 clusters)

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