1. BTeV Beam Test Results Jianchun Wang Syracuse University Representing J.A. Appel, J.N. Butler, G. Cardoso, H. Cheung, G. Chiodini, D.C. Christian, E.E. Gottschalk, B.K. Hall, J. Hoff, P. A. Kasper, R. Kutschke, S.W.Kwan, A. Mekkaoui, R. Yarema, and S. Zimmermann Fermi National Accelerator Laboratory C. Newsom - University of Iowa A. Colautti, D. Menasce, and S. Sala - INFN(Milan) R. Coluccia and M. Di Corato - Universita’ di Milano M.Artuso and J.C. Wang – Syracuse University VERTEX 2000 Sep 10 - 15, 2000 Homestead, Michigan

2. VERTEX 2000Jianchun (JC) Wang2 The BTeV Detector Pixel Vertex Detector Dipole Magnet Magnet Coil Beam Pipe Forward tracking RICH PbWO 4 EM calorimeter Muon Toroid

3. VERTEX 2000Jianchun (JC) Wang3 The BTeV Pixel Detector  Function:  Deliver clean, precise space points to detached vertex trigger  Provide vertex information for offline analysis  Pixel sensor  Eliminate ambiguity problems with high track density (essential to the detached vertex trigger)  Radiation hard, low noise  Easy pattern recognition  Pixels size: 50  m  400  m (total 3  10 7 channels) 0.5 cm 31 2-plane pixel stations

4. VERTEX 2000Jianchun (JC) Wang4 Goals of Beam Test  Gain operational experience, look for potential problems and sensitivities  Study the spatial resolution dependence on track incident angle, digitization accuracy, bias voltage and threshold  Determine validity of our sensor simulations  Compare different detector technologies (p-stop, p-spray)

5. VERTEX 2000Jianchun (JC) Wang5 Beam Test Telescope  Beam: 227 GeV   Tracking: 6 plane SSD in two boxes  SPD box provides different incident angle: 0, 5, 10, 15, 20, 30 degree  4 SPD tested with ATLAS sensor prototypes  227 GeV SSDSPDSSD X-Y-X

6. VERTEX 2000Jianchun (JC) Wang6 Silicon Pixel Detector Readout Chip  FPIX0: 64  12 cells, 8-bit external ADC  FPIX1: 160  18 cells, 2-bit internal FADC Pixel sensor (n + np + )  ST1-CiS p-stop (FPIX0)  ST2-CiS p-spray (FPIX0)  ST1-Seiko p-stop (FPIX1)  ST2-Seiko p-spray (FPIX1)

7. VERTEX 2000Jianchun (JC) Wang7 Front End Electronics  FPIX0: analog output, with external 8-bit ADC  FPIX1: digital output, with internal 2-bit FADC FPIX0 Inner Board Analog Buffer 8 bit ADC See David Christian’s talk

8. VERTEX 2000Jianchun (JC) Wang8 Pulser Calibration FPIX0 bump-bonded to ST1 CiS p-stop sensor  Threshold: 2500 e Noise: 106 e  External ADC introduce noise: Total: 400 e Q th =2500  e - Q noise =106  e - Q noise,ADC =400  e - Dynamics  MIP

9. VERTEX 2000Jianchun (JC) Wang9 X-ray Source Calibration Absolute Calibration Discriminator threshold Amplifier noise ADC scale

10. VERTEX 2000Jianchun (JC) Wang10 Charge Collection Peak: 24.7 ke FWHM: 10 ke FPIX0 p-stop Pulse Height Saturation bump for CS=1 Less than 0.7% with Q < 15 ke

11. VERTEX 2000Jianchun (JC) Wang11 Charge Collection Q mp = 18300 e Charge loss not intrinsic to the p-spray technology, but a feature of this particular sensor – “punch-through biasing”, and floating atoll FPIX0 p-spray

12. VERTEX 2000Jianchun (JC) Wang12 MC Simulation The interplay of these factors has been studied with a Monte Carlo simulation including: ee Track E  Energy deposition by charged track along its path length (spread of the electron cloud due to diffusion)  Drift in E corresponding to doping and bias voltage applied  E  B (our sensors will be in dipole field of 1.6 T)  Realistic parameters of the front end electronics (noise,threshold, digitization accuracy)

13. VERTEX 2000Jianchun (JC) Wang13 Charge Sharing FPIX0 CiS p-stop Q th = 2500 e  V bias =  140V V bias =  85V Relative Fraction of Cluster Size Delta ray emission results in larger cluster size

14. VERTEX 2000Jianchun (JC) Wang14 Position Reconstruction  Error of predicted track position ~ 2  m - 2.5  m, Not subtracted from measured resolution  Charge weighting and s-curve correction used for clusters with 2 or more pixels 

15. VERTEX 2000Jianchun (JC) Wang15 Charge Sharing Non-Gaussian residual distribution for 1-pixel cluster  Resolution fit needs to consider the special shape  For small incident angle tracks, the fraction of 1-pixel clusters is proportional to spatial resolution

16. VERTEX 2000Jianchun (JC) Wang16 Resolution vs angle  No track projection error subtracted from the measurement  Resolution distribution agrees with simulation  Binary resolution degraded from 8-bit ADC FPIX0 p-stopFPIX1 p-stop

17. VERTEX 2000Jianchun (JC) Wang17 Resolution Oscillation Binary Readout Resolution oscillation in binary mode due to change of dominant cluster size Simulation

18. VERTEX 2000Jianchun (JC) Wang18 Comparison of Different Detector  Most of difference due to the different readout thresholds  The charge losses in FPIX0 p-spray degrades the spatial resolution  BTeV requirement: better than 9  m

19. VERTEX 2000Jianchun (JC) Wang19 Digitization Accuracy  “2 bit” ADC is degraded from 8-bit ADC  Resolution of 2-bit ADC is slightly worse than 8-bit  FPIX2 will use 3- bit FADC FPIX0 p-stop

20. VERTEX 2000Jianchun (JC) Wang20 Resolution vs Bias Voltage For 0° track, lower V bias  more diffusion  less fraction of N pixel =1  better resolution

21. VERTEX 2000Jianchun (JC) Wang21 Resolution vs Threshold FPIX0 p-stop Large readout threshold degrades the spatial resolution

22. VERTEX 2000Jianchun (JC) Wang22 Occupancy Test Interaction vertex in diamond targetInteraction vertex in pixel plane  2.2 mm thick diamond target used  Handle occupancy much larger than expected at BTeV ( ~ factor of 10 )

23. VERTEX 2000Jianchun (JC) Wang23 Summary  Large data sample to gain operational experience with pixel silicon detectors (~ 3M events)  The FPIX type front end electronics performs well  Resolution has little sensitivity to the bias voltage, but sensitive to readout threshold  Good resolution at all angles, meets 9  m requirement, and 3-bit ADC is a good choice for FPIX2  Excellent tracking capability, can easily handle the BTeV multiplicity by 50  m  400  m pixels  Monte Carlo simulation describe well the real feature

24. VERTEX 2000Jianchun (JC) Wang24 Charge Sharing FPIX0 CiS p-stop Q th = 2500 e  V bias =  140V V bias =  85V Relative Fraction of Cluster (row) Size Delta ray emission results in larger cluster size

25. VERTEX 2000Jianchun (JC) Wang25 Charge Sharing FPIX1 Seiko p-stop Q th = 3780 e  V bias =  75V V bias =  45V Relative Fraction of Cluster (row) Size Delta ray emission results in larger cluster size