Post on 30-Dec-2015
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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
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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!