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Tracking R&D at SCIPP: Charge Division with Microstrips Ladder Length Limitations

Tracking R&D at SCIPP: Charge Division with Microstrips Ladder Length Limitations. 2011 Linear Collider Workshop, Granada, Espana 26-30 September 2011 Bruce Schumm SCIPP/UC Santa Cruz. But: practical detectors aren’t isolated strips. Include two nearest-neighbors in simulation:.

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Tracking R&D at SCIPP: Charge Division with Microstrips Ladder Length Limitations

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  1. Tracking R&D at SCIPP: • Charge Division with Microstrips • Ladder Length Limitations 2011 Linear Collider Workshop, Granada, Espana 26-30 September 2011 Bruce Schumm SCIPP/UC Santa Cruz

  2. But: practical detectors aren’t isolated strips. Include two nearest-neighbors in simulation: Network ef-fects lead to ~5% reduction in longitudinal resolution, but anti-correlation reduces from 60% to 40%  Single-strip results also apply for multi-strip sensors, essentially unchanged.

  3. Areas of Activity

  4. Limitations on Ladder Length Long ladders with precise resolution is unique to the ILC. What constrains ladder length? What limitations arise for maximal lengths?  Design considerations

  5. Typical electronics characterization: e vs. capacitive load S:N ~ 16:1 ~ 1m  Suggest ladder lengths > 1m easily achieved

  6. Standard Form for Readout Noise; Lumped Element Approximation (Spieler) Series Resistance Parallel Resistance Amplifier Noise (parallel) Amplifier Noise (series) Dominant term for long ladders (grows as L3/2) Fi , Fv are signal shape parameters that can be determined from average scope traces.

  7. Expected Noise vs. Ladder Length “Lumped element” Load Series noise expected to dominate for narrow (50 m) pitch sensors above ~25 cm long

  8. Lumped approximation implies significant limitations due to strip resistance • How accurate is this approximation? • Test with extensible, ILC-like ladder • SiD 50 m pitch “Charge Division” Sensors • 4.75 cm strip length • 287  per strip (~ 8 m width) • 5.2 pF per strip

  9. Sensor “Snake” Sensor “Snake”: Read out up to 13 daisy-chained 4.75 cm sensors (with LSTFE-1 ASIC) LSTFE1 chip on Readout Board Can read out from end, or from middle of chain (“center-tap”)

  10. Time-Over-Threshold (TOT) Readout: the LSTFE • Pulse-development simulation  no loss of accuracy for TOT readout (relative to direct ADC conversion) • Targets low-complexity, long-ladder tracking solution • Real-time readout stream favorable for forward tracking also • LSTFE-I prototype relatively successful; LSTFE II under testing. Upgrades relative to LSTFE-I include • Improved environmental isolation • Additional amplification stage to improve S/N, control of shaping time, and channel-to-channel matching • Improved control of return-to-baseline for < 4 mip signals (time-over-threshold resolution) • 128 Channels (256 comparators) read out at 3 MHz, multiplexed onto 8 LVDS outputs

  11. Li Hi Li+1 Hi+1 Li+2 Hi+2 Li+3 Hi+3 Li+4 Hi+4 Li+5 Hi+5 Li+6 Hi+6 Proposed LSTFE Back-End Architecture Low Comparator Leading-Edge-Enable Domain 8:1 Multi-plexing (clock = 50 ns) FIFO (Leading and trailing transitions) Event Time Clock Period  = 400 nsec

  12. Some early results: TOT respone Time over Threshold (s) Time over Threshold (s) Very uniform response for large pulses; increased sensitivity in min-i region Minimum ionizing region

  13. More early results: Noise v. Capacitive Load Result at 100 pF (optimization point): 1375 electrons noise, but without detector resistance (distributed RC network)

  14. Standard Form for Readout Noise (Spieler) Series Resistance Parallel Resistance Amplifier Noise (parallel) Amplifier Noise (series) Dominant term for long ladders (grows as L3/2) Fi , Fv are signal shape parameters that can be determined from average scope traces.

  15. Long-Ladder Readout Noise Probe conventional notions about dependence of readout noise on distributed capacitance and series resistance

  16. Expected Noise vs. Ladder Length Series noise expected to dominate for narrow (50 m) pitch sensors above ~25 cm long

  17. Sensor “Snake” Sensor “Snake”: Read out up to 13 daisy-chained 5cm sensors (with LSTFE-1 ASIC) LSTFE1 chip on Readout Board Can read out from end, or from middle of chain (“center-tap”)

  18. PSpice predictions End readout (include network effects) Center tap First-Pass Results vs. Expectations (old…) Expected for end readout (Spieler formulation) Observed: End readout Center tap But: need to add in amplifier noise…

  19. Observed noise Simulation, with LSTFE series and parallel noise Network values: 65 pF; 3700  Simulation, with LSTFE series noise only Include realistic feedback network; measured LSTFE-I noise (LSTFE-II now known to be similar) Good agreement; significantly less than naïve expectation Need to look at “center-tap” readout next.

  20. Non-Prompt Tracking with the SiD Explore performance via explicit signature: Metastable stau NLSP (Gauge-Mediated SUSY)

  21. Reconstructing Metastable Staus w/ SiD • Gauge-Mediated SUSY • Large tract of parameters space as stau NLSP • Metastable (cstau ~ centimeters) is in cosmologically preferred region • Process is • with

  22. Reconstructing Metastable Staus w/ SiD Started with: 5+1 layers for inside track 4 layers for outside track New result: Include VTX-only inside track

  23. Measuring Staus with the SID • Stau sample: • 11.1 fb-1 of e+e- stau pairs with • mstau = 75 GeV • Ecm = 500;  = 90 fb • c = 23 cm • Background sample: • 5.3 fb-1 combined SM background

  24. Reconstructing Metastable Staus w/ SiD Focus initially on rdecay = 22-47 cm… Reconstruct decays by requiring:     - Outer hit of inner trk on last VXD or 1st tracker layer     -  1 missing layer between inner & non-prompt trks    - Both tracks on the same side of the Barrel (in z)     - Tracks have a geometric intersection in the x-y plane And: When inside track has  1 Central Tracker Hit     - The sign of the track curvatures match     - Non-prompt track curvature larger than the primary Of 897 staus with 6cm < rdec < 47cm, 642 staus are reconstructed, of which 592 truth-match

  25. Stau Reconstruction Efficiency Truth-Matched Staus

  26. Signal to Background for 10 fb-1

  27. Signal to Background (10 fb-1) Kink angle Curvature ratio

  28. Signal to Background (10 fb-1) pT of inside track #Prompt Tracks/event Good separation between signal and background for #prompt tracks/event and inside track pt  Require, e.g., fewer than three prompt tracks

  29. Signal to Background (After <3 Track Requirement) Essentially no background after three-track cut  Next challenge: 46 < rorg < 71 cm (3 tracker hits)

  30. Wrap-Up Time-Over-Threshold Readout (LSTFE) Second prototype under study in lab; functionality looks good (except for power cycling) Long Ladder Readout Noise: Measurements show much lower noise than naïve (lumped-element) analysis. Now confirmed with simulation  promising for long-ladder solutions. Non-Prompt Tracks with SiD: Extended radial range of stau decay kinks from 21-46 cm to 6-46 cm, maintaining good efficiency and purity. Exploring 46-71 cm range.

  31. (No) Backup Slides

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