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!