1. August 26, 2003P. Nilsson, SPD Group Meeting1 Paul Nilsson, SPD Group Meeting, August 26, 2003 Test Beam 2002 Pixel Response Simulation: Update Jan Conrad (CERN, Pixel Group) SPD general meeting November, 2004

2. August 26, 2003P. Nilsson, SPD Group Meeting2 Side remark  Ivanov’s talk: parameterization of errors on reconstructed points reconstructed points if response working, this can be done by MC (true-rec for different cluster sizes) MC (true-rec for different cluster sizes)  get parameterizations as function of incident angle and different cluster sizes.  get parameterizations as function of incident angle and different cluster sizes. Simulation  Reconstruction Probably better: data analysis see talks of Domenico, Daniela,Pål

3. August 26, 2003P. Nilsson, SPD Group Meeting3 Contents  Main news:  Diffusion is included and working

4. August 26, 2003P. Nilsson, SPD Group Meeting4 Diffusion in AliRoot (Dubna) model  Energy is deposited in steps in the sensor volume (15-20 steps)  Charge sharing done by diffusion (see next slide).  Dependence on bias voltage.

5. August 26, 2003P. Nilsson, SPD Group Meeting5 Diffusion  Gaussian diffusion: charge cloud spreads out during the particle’s traversion  σ diff = k (T l dr, ) 1/2  k = (2D/v dr ) 1/2 D = 11cm 2 /s  v dr = μ  E μ = 450 cm 2 /Vs  E = V bias /d sensor σ diff  d sensor / √V bias ≈ 5 – 15 μm σ diff  d sensor / √V bias ≈ 5 – 15 μm

6. August 26, 2003P. Nilsson, SPD Group Meeting6 What is in the simulation @ present (default) ?  Charge sharing geometrical (Ba/Sa model)  Coupling parameters: 0. (no coupling)  Threshold: 2000 e,  noise/threshold 280 e  no dependence on bias voltage  no dependence on temperature

7. August 26, 2003P. Nilsson, SPD Group Meeting7 Geometry 2002 Trick: whole ladder Si (for segmentation, BN) No scintillators,no PCB VTT ladder: 300μ Chip: 725 μ Telescope: 300 μ Chip: 725 μ

8. August 26, 2003P. Nilsson, SPD Group Meeting8 Simulation  assume 300 mu detector, 80 V bias  threshold: 2300 e, Noise: 300 e  file:  file: biasscan_chip03_th200_14-07 2002.root

9. August 26, 2003P. Nilsson, SPD Group Meeting9 Cluster Sizes including diffusion Long dimensionShort dimension

10. August 26, 2003P. Nilsson, SPD Group Meeting10 How does it look without diffusion? No diffusiondiffusion

11. August 26, 2003P. Nilsson, SPD Group Meeting11 Scans (slide taken from last SPD general meeting) Angle Scan Threshold Scan Data Simulation BIAS VOLTAGE?

12. August 26, 2003P. Nilsson, SPD Group Meeting12 Scans: present status

13. August 26, 2003P. Nilsson, SPD Group Meeting13 δ rays  Generated on correct level:  rule of thumb: 1 δ ray per mm Si per incident particle. 

14. August 26, 2003P. Nilsson, SPD Group Meeting14 Status summary and outlook  Cluster sizes 1 and 2 reproduced (zero tilt)  There is still a problem with cls >3  Trigger simulation  more material details  FLUKA (M. Noriega)  More long term:  more effective diffusion routine ( CPU diff/nodiff = 7)  2003 !