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BESIII TOF Simulation

BESIII TOF Simulation. Deng Ziyan Jan 10-12, 2006 BESIII Collaboration Meeting. Outline. TOF geometry Geant4 hits recording Digitization based on hits Light production Light propagation PMT response Discrimination. Barrel TOF. End-cap TOF. EMC. TOF Geometry.

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BESIII TOF Simulation

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  1. BESIII TOF Simulation Deng Ziyan Jan 10-12, 2006 BESIII Collaboration Meeting

  2. Outline • TOF geometry • Geant4 hits recording • Digitization based on hits • Light production • Light propagation • PMT response • Discrimination

  3. Barrel TOF End-cap TOF EMC TOF Geometry • Dimensions and materials same as designed • Scintillator (EJ200) • Wrapping materials (Al + PVF) • PMT (R5924) barrel end-cap

  4. Geant4 Hits • Geant4 hits recorded at discrete steps along track • Global time, step time, position, direction • scintillator ID, energy loss… hit 0.8 GeV/c electron perpendicular incidence

  5. Digitization based on hits Geant4 Get hit information: energy loss, time, position Scintillator Scintillator light emission Light propagation PMT Photoelectrons production Signal pulse generation Discriminator output TDC and ADC Digitization

  6. Characteristic Parameters

  7. Simulation of Light Emission • Light uniformly emitted along step • Isotropic angular distribution • Number of photons proportional to energy loss • Emission time rise time = 0.9 ns

  8. Simulation of Light Propagation

  9. Collection Factors (1) Light atttenuation inscintillator (3) Response of incident angle at PMT front glass (2) Mismatch between scintillator and PMT Average: 66% 40%

  10. Collection Factors Quantum efficiency of PMT photocathode (4) (5) Collection factor of PMT dynode:60% number of generated photoelectrons 20%

  11. Time Distribution time of photoelectrons

  12. PMT Response time response function for single photoelectron signal rise time=2.5ns PMT signal pulse MeanPulseHeight=50mv

  13. LT TDC Preamplifier and Discriminator Preamplifier: TDC and ADC MeanPulseHeight=500mv electronic noise added rise time:4ns low threshold (LT) = 50mv high threshold (HT)= 250mv

  14. Time Walk before T-Q correction after T-Q correction 0.8GeV electron, perpendicular incidence

  15. Effective speed Veff = 17.7 cm/ns Intrinsic time resolution at z=0 : 85 ps beam test result Effective attenuation length λ= 318cm

  16. More to do • Add uncertainty from start point • start position • start time t0 • More research on end-cap TOF digitization

  17. The end Thanks!

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