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Tracking R&D at SCIPP: Charge Division Long Ladder Readout Noise Non-Prompt Tracks with SiD

Explore the measurement of longitudinal coordinates with microstrip sensors, investigate the effects of charge division, long ladder readout noise, and reconstruct non-prompt tracks using SiD. This research was presented at the CERN Linear Collider Workshop in October 2010.

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Tracking R&D at SCIPP: Charge Division Long Ladder Readout Noise Non-Prompt Tracks with SiD

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  1. Tracking R&D at SCIPP: Charge Division Long Ladder Readout Noise Non-Prompt Tracks with SiD CERN Linear Collider Workshop October 18-22 2010

  2. Charge Division Can a longitudinal coordinate be measured with microstrip sensors? Explore with PC-board microstrip mock-up and PSpice simulation

  3. Final step: practical detectors are not isolated strips. Include two nearest-neighbors in simulation: Network effects lead to ~5% reduction in longitudinal resolution.

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

  5. 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.

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

  7. 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”)

  8. PSpice predictions End readout (include network effects) Center tap Comparison of Results and Expectations Expected for end readout (Spieler formulation) Observed: End readout Center tap PSpice simulation is “first pass” (crude amplifier model; parasitic effects not yet incorporated, etc.)

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

  10. 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

  11. Reconstructing Metastable Staus w/ SiD Start with: 5+1 layers for inside track 4 layers for outside track  Restricted range in rdecay for now; will expand soon

  12. 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

  13. Reconstructing Metastable Staus w/ SiD Focus initially on rdecay = 22-47 cm… Reconstruct decays by requiring:     - Outer hit of primary track on first tracker layer     - Inner hit of non-prompt track on second tracking layer    - Both tracks be on the same side of the Barrel (in z)     - The sign of the track curvatures match     - Non-prompt track curvature larger than the primary     - Tracks have a geometric intersection in the x-y plane Of 294 staus with 22<rdec<27 and |cos| < 0.5, 239 staus are reconstructed, of which 232 truth-match

  14. Stau Reconstruction Efficiency Truth-Matched Staus

  15. Signal to Background for 10 fb-1 Truth-matched stau: 210 Background kinks: 1338 Perhaps slight preference for background kinks to show up at material layers at 22 and 47 cm 47cm 22cm

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

  17. Signal to Background (10 fb-1) pT of prompt track #Tracks/event Good separation between signal and background for #tracks/event and track pt

  18. Wrap-Up Charge Division: Longitudinal resolution of z=6mm seems achievable for a 10cm-long sensor. Long Ladder Readout Noise: Simulation and data show significantly less readout noise for long ladders than expected. “Center-tapping” yields even further reductions. Non-Prompt Tracks with SiD: Reconstructing clean metastable stau signature between first and second tracking layer seems quite plausible. Beginning to look in different radial regions.

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