BESIII EMC Simulation & Reconstruction
He Miao2006-1-10
Outline
Emc simulationDetector constructionSensitive detector and hitsDigitization
Emc reconstructionEvent modelData flowAlgorithm
Preliminary performances
Emc Simulation Detector description
Crystal, casing, PD (silicon photodiode), pre-amplifier box, cable, support system.
Use G4Trap to construct barrel crystals, and introduce G4IrregBox which is not provided by Geant4 to construct endcap crystals.
barrel
endcap
Emc Simulation
Sensitive detectorCrystalPD (unfinished)
HitRecord signal in sensitive detector, including
energy, time, position, copy number, etc.
Emc Digitization
Pick up hits in the same crystal, and add their energy together.
Add photon statistics. Simulate the readout electronics. Add noise. Add background (unfinished). Get ADC and TDC channel.
Simulation of Emc readout electronics
Calculate the frequency response function of the electronics through the Laplace transform.
Acquire the waveform in time domain produced by main amplifier via the inverse Laplace transform.
Simulate the sampling and peak searching process by Flash ADC to obtain the energy and time information.
Pre Amp
Main Amp
FlashAD
C
CsI Photodiod
eenergy
deposited
time information
peaksearching
Emc Reconstruction
Event model Data flow Algorithm
ClusteringShower splittingShower attributes
Energy and position correction
Event ModelEmcRecDigitEmcRecIDEmcRecADCEmcRecTDC
EmcRecHitEmcRecIDEmcRecEnergyEmcRecTime
EmcRecDigitMap
EmcRecHitMap
EmcRecClusterMap
EmcRecShowerMap
EmcRecFractionEmcRecFrac
EmcRecClusterEmcRecClusterIDEmcRecHitMap
EmcRecShowerEmcRecShowerIDEmcRecClusterIDEmcRecFracMapEAll, ESeed, E3x3, E5x5Position, Nearest-Seed
EmcRecFracMap
Data Flow
i-1 i,j i+1
j-1
j+1
Clustering find connected regions
Neighbor definition –barrel: 3x3
Red, green and blue are neighbors
Neighbor definition –endcap
Various amounts of neighbors: 8,7,6,5…
Shower Splitting
e2
e1
e3
Seed – local maximum. If one seed, cluster = shower. If more seeds, the cluster
should be splitted into several showers. Hit in this cluster is shared by every shower.
e3=(e3*weight1+e3*weight2)/(weight1+weight2)
Shower Attributes
Energy ESeed E3x3 E5x5 EAll
Position
Linear weighting function
Logarithmic weighting function
N N
c j j j j jj j
x w E x w E
( )linearj j jw E E
( )00, ln lnlog
j j j totw E Max a E E
Energy Correction
correction parameters energy spectrum
Position Correction (unfinished)
σx=4.8mm
Use bhabha events with information of track extrapolation to get correction parameters.
Theta resolution of single gamma with 1GeV momentum after correction.
Emc Performances
Energy and position resolution (barrel) Energy and position resolution (endcap) π0 mass resolution and detect efficiency e /π separation Execute time
Energy Resolutionsingle gamma
4E/E=[(p0/E) (p1/ E) p2]%
Position Resolution (by Yang Ming) use Logarithmic weighting function
theta phi
Endcap Performances1GeV gamma
west end east end
σE/E
theta(cm)
phi(cm)
π0 mass resolution and detect efficiency
π0 detect efficiency: events ratio between the peak of π0 mass spectrum +- 3.0σπ0 .
e /π separation
energy deposited in Emc of 1GeV e- and π-
Execute Time (by Sun Yongzhao)
Happy new year!