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BESIII TOF Digitization

Deng ziyan

2005.10.26

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Outline

TOF GeometryTOF Digitization version 1TOF Digitization version 2Something about running BOOST

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TOF Geometry

0

88

Wrapping

Al + PVF

layer1

layer2

barrel

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TOF Geometry

end-cap

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Digitization from hits

digi

digi

digi

digi

Hit

Hit

Hit

Hit

Hit

Hit

Hit

edep

time

positionevent

digitization

forwTDC

backTDC

backADC

forwADC

No backward output for endcap tof

forward: east backward: west

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Digitization Version 1

Select Arrival Time

• Select first Arrival time• Apply dE/dx threshold cut

edep, arrivalTime 1

edep, arrivalTime 2

edep, arrivalTime n

edep (1)

edep (2)

edep (n)

izn

i i

ie

dx

dEzf )(

edep to ADC

ADCarrivalTime (initial)

PMT resolution

tdc smeared by Gaussian with (f(ADC))

Time walk added

TDC = tdc + c(ADC)-0.5

tdc ADC

ADC

TDC

GeantGeant

Tof digitizationTof digitizationedep :-dE/dx in scintillatorarrivalTime : time of flight + dz/vel

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Digitization Version 1

1GeV e-Theta=90Phi: 0-360Sigma = 84 ps

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More to do about version 1

Correction on ADC and TDCADC vs z-hitTDC Resolution vs ADCTime-walk correction

TDC vs ADC

Parameters will be taken from data fitting

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Digitization Version 2

Full simulationScintillation light emission in each stepLight propagation in scintillator upto PMTPMT response

Photoelectron production Signal pulse production

Discrimation of PMT signal at two levels If pulse height>HL, then make T,Q output

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Parameters

ScintillatorEmit time parametersLight attenuation lengt

hRefractive indexLight output

PMTGainRise timeEffective areaTransit time(and sprea

d)Collection factorQuantum efficiencyHL, LL

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Scintillation light emission

Number of photons is proportional to edep10000/MeV

Uniform distributionEmission time: a time

profile assumed

temit

2 1

3

/ //

2 1 3

1( ) ( )

1

emit emit

emit

t tt

emit

e e RE t e

R

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Light propagation

Lpro = d / cosθ

Propagation time: tpro= Lpro/ vel

Attenuation in TOF counter is simulated

Part Lights escape or lost

PMT

d

θ

/( ) pro proLproR L e

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PMT response

Photoelectron productionPhotoelectrons are produced with quantum

efficiencyNumber of photoelectrons is reduced due to the

dynode structureTransit time is added

PMT response for single photon electron2 2

2 2

2 /

2 /( )

t

e t

t ev t GC

t e dt

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Photon 1

………..

Photon N

Hit 1 direction Path length Pro time

reach PMTTransit time end time

endTime = flightTime+emitTime+ProTime+TransitTime

…..

Hit N

PMT response

1

( )pen

PMT ii

V v t

Integration of arrival photon times with PMT response function

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PMT response

PMT response for single pe

Rise time = 2.5 ns

endTime

PMT pulse output

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Time distribution

flight time delta T in one step

1GeV/c e- vertical incidence

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Time distribution

emitting time propagation time

1GeV/c e- vertical incidence

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Time distribution

PMT transit time end time

1GeV/c e- vertical incidence

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Simulation of readout electronics

Each PMT signal is examined using double threshold (LL,HL)

A signal larger than HL threshold provides a gate to measure TDC

TDC is given at the moment when PMT pulse crosses LL threshold

HL

LL

( ) /PMTADC V t dt R

TDC

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TOF Front_End Electronics

1: 3 spl i t 1: 3 spl i t

Leadi ng EdgeDi scri m. wi thl ow threshol d

Leadi ng EdgeDi scri m. wi th

hi gh threshol d

Leadi ng EdgeDi scri m. wi thl ow threshol d

Leadi ng EdgeDi scri m. wi th

hi gh threshol d

ADCADCHPTDC HPTDCMean Ti mer

PMT2PMT1 176 × Barrel TOF

L1 Tri gger L1 Tri gger

To Tri gger Modul e

gate gate

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1GeV/c e- vertical incidence

total energy loss in one scintillator (5cm width)

Energy deposit

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e- 1GeV/c Z=0 : forward TDC resolution = 121.6ps backward TDC resolution = 121.4ps

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TDC vs z-hit

forward Veff=17.16 cm/ns backward Veff=17.19 cm/ns

0 0, 20.29t t kz t

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β vs Pe

μπ

K

P

( / )

( / )

20.29 2.782 17.508( )

0.5*( 2* )

2 /(( 35.016)*150)

eff

eff

forwTDC TOF const z v

backTDC TOF const z v

const ns

TOF backTDC forwTDC const

trackL forwTDC backTDC

particles: random

P: 0-1.6GeV random

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ADC vs z-hit

log(forwADC/backADC) vs z-hit

26/29

2 21 2 1 2/

TDC sigma vs z-hit

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besfarm Genbes BOOST

lxplus Genbes BOOST

koala BesGenModule BesSim

lxplus BesGenModule BesSim

Running environment

besfarm: old, no maintenance koala: overwhelmed lxplus: the last choice! even problems exist Using BesGenModule and BesSim can avoid changing environment

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Running environment

lxplus04, 05/ihepbatch/bes/dengzy/afs/ihep.ac.cn/users/d/dengzy (2G)/ihepbatch/besdata/public/dengzy (5G)

more documentG4ParticleListGenbesParticleIdPDGscheme

http://boss.ihep.ac.cn/SofPro/simulation.html

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The end

Thanks!