TRD Response Simulation

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TRD Response Simulation
TRD Software Meeting Oct 23, 2003 Ken Oyama,
Heidelberg
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• Done
• Eth was different between GEANT(10 keV) and
  StepManager(50 keV) and it was causing overlap.
• Now both DCUTE50 keV and CUTELE50 keV.
• This suppresses number of secondary electrons
  generated in TRD gas to be 1/6 (180 to 30 of
  primary).
• Checked what happen if gMC-gtEdep() (destep) is
  used instead of Ermilova.
• Checked what happen if Poisson distribution is
  used for determining Q.
• On Going
• Implementation of Ermilova (or something better)
  into GEANT.
• Check whether fluctuation is simulated
  correctly or not.
• Check about GEANT parameterization. Simulate it
  in StepManager.

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Momentum Dependence
Absolute value in the simulation is higher than
test beam data.
AliRoot
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Bethe Bloch and Step Size
In TPC, step size is typically order of 1 mm. In
TRD, 0.1 mm.
Step size cm for 2 GeV/c pion
Number of primary collision /cm
TPC
TRD
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Delta Electron Spectra Simulated in Our
StepManager
Red Ermilova function (default) Blue Geant
Edep (restricted continuous energy loss)
Threshold 10 keV
Threshold 50 keV
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dE/dx Simulation Method in Geant3 and StepManager
GEANT delta electrons of energy ? gt Eth
gas volume
primary collision
E
E- ?
Step size given by Bethe Bloch dNprim/dx
StepManager virtually generates delta electron
with energy Edelta according to Ermilova. Number
of charge generated by a primary collision is
calculated by Q (Edelta Kpot) / W 1. Then a
hit with Q at rest is generated ? dE/dx
ltEdeltagt dNprim/dx.
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Particles Generated in the TRD Delta Electron
Spectra
Factor 6 smaller delta electron yield for 50 keV
threshold.
These shapes seamlessly connect to the Geant Edep
shape.
DCUTE10 keV
DCUTE50 keV
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Q calculation
K 12 eV ltWgt 22 eV
Original method Q (int) 1 (Edelta K) /
ltWgt. Modified method Q 1 P(Edelta ltWgt)
/ ltWgt where P(m) is discrete Poisson
distribution with mean m.
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Comparison
Hit charge sum times 22 eV / 6 chambers energy
deposit in one chamber
Same as a plot in previous page