1. The Gossamer Tracker: A Novel Concept for a LC Central Tracker Bruce Schumm SCIPP & UC Santa Cruz UC Davis Experimental Particle Physics Seminar June 3, 2002

2. “We recommend that the highest priority of the U.S. program be a high-energy, high-luminosity electron- positron collider, wherever it is built in the world. This facility is the next major step in the field, and should be designed, built, and operated as a fully international effort.” Fall 2001 recommendation of the High Energy Physics Advisory Panel (HEPAP) to the Department of Energy’s Office of Science: The LC group at SCIPP has been re-energized by this endorsement, and has continued to bolster its efforts with both public outreach and international cooperation.

3. TESLA NLC

4. Linear Collider Physics At leading order, the LC is a machine geared toward the elucidation of Electroweak symmetry breaking. Need to concentrate on: Precision Higgs Physics Strong WW Scattering SUSY

5. Reconstructing Higgsstrahlung ++ -- Haijun Yang, Michigan M  for  p  / p  2 = 3x10 -5

6. Strong WW Scattering Absent Higgs Sector, something else must act to renormalize W couplings Diagrams: Wolfgang Killian, Karlsruhe This physics will be produced via the t-channel  will tend to be forward

7. W/Z Separation Henri Videau; Ecole Polytechnique Jet energy resolution requires energy-flow technique: excellent track/cluster matching to allow charged track energies to come from tracker

8. Precise Reconstruction of SUSY Haijun Yang; Michigan Precise recon- struction of sparticle masses relies on precise determination of endpoint  p  / p  2 = 2x10 -5 But does not establish as tight a requirement as Higgs physics

9. The North American Detectors L Design: Gaseous Tracking (TPC) R max = 190cm 3 T Field Conventional (Pb/Sci) Calorimeter S Design: Solid-State Tracking R max = 120cm 5 T Field Precise (Si/W) Calorimeter

10. The Trackers The SD-MAR01 Tracker

11. Tracker Performance SD Detector burdened by material in five tracking layers (1.5% X 0 per layer) at low and intermediate mo- mentum Code: http://www.slac.stanford.edu/~schumm/lcdtrk.tar.gz

12. Idea: Noise vs. Shaping Time Min-i for 300  m Si is about 24,000 electrons Shaping (  s) Length (cm)Noise (e - ) 11002200 12003950 31001250 32002200 101001000 102001850 Agilent 0.5  m CMOS process (qualified by GLAST)

13. The Gossamer Tracker Ideas: Long ladders  substantially limit electronics readout and associated support Thin inner detector layers Exploit duty cycle  eliminate need for active cooling  Competitive with gaseous track- ing over full range of momenta Also: forward region…

14. TPC Material Burden

15. Pursuing the Long-Shaping Idea LOCAL GROUP SCIPP/UCSC Optimization of readout & sensors Design & production of prototype ASIC Development of prototype ladder; testing  Supported by 2-year, $95K grant from DOE Advanced Detector R&D Program SLAC System performance studies (backgrounds, pattern recognition, vees, etc.) Mechanical considerations

16. PRC Meeting DESY, Hamburg, May 7 and 8, 2003 SilC: an International R&D Collaboration to develop Si-tracking technologies for the LC Aurore Savoy-Navarro, LPNHE-Universités de Paris 6&7/IN2P3-CNRS, France on behalf of the SiLC Collaboration

17. The SiLC Collaboration Brookhaven Ann Arbor Wayne Santa Cruz Helsinki Obninsk Karlsruhe Paris Prague Wien Geneve Torino Pisa Rome Barcelona Valencia Korean Universities Seoul &Taegu Tokyo Europe USA ASIA So far: 18 Institutes gathering over 90 people from Asia, Europe & USA Most of these teams are and/or have been collaborating.

18. Roles in the Larger Community Discussions with Aurore Savoy-Navarro (LPNHE Paris) Finite element (thermal, mechanical) modelling Development of mechanical systems Collaboration on ASIC development University of Michigan Interferometric alignment systems

19. The SCIPP/UCSC Effort Faculty/Senior Alex Grillo Hartmut Sadrozinski Bruce Schumm Abe Seiden Post-Doc Gavin Nesom (half-time LC postdoc from 1999 program) Student Christian Flacco (will do BaBar thesis) Engineer: Ned Spencer (on SCIPP base program)

20. SCIPP/UCSC Development Work Characterize GLAST `cut-out’ detectors (8 channels with pitch of ~200  m) for prototype ladder Detailed simulation of pulse development, electronics, and readout chain for optimization and to guide ASIC development (most of work so far)…

21. Pulse Development Simulation Long Shaping-Time Limit: strip sees signal if and only if hole is col- lected onto strip (no electrostatic coupling to neighboring strips) Charge Deposition: Landau distribution (SSSimSide; Gerry Lynch LBNL) in ~20 independent layers through thickness of device Geometry: Variable strip pitch, sensor thickness, orientation (2 dimen- sions) and track impact parameter

22. Uncorrelated Sampling Check

23. Carrier Diffusion Hole diffusion distribution given by Offest t 0 reflects instantaneous expansion of hole cloud due to space-charge repulsion. Diffusion constant given by Reference: E. Belau et al., NIM 214, p253 (1983)  h = hole mobility

24. Other Considerations Lorentz Angle: 18 mrad per Tesla (holes) Detector Noise: From SPICE simulation, normalized to bench tests with GLAST electronics Can Detector Operate with 167cm, 300  m thick Ladders? Pushing signal-to-noise limits Large B-field spreads charge between strips But no ballistic deficit (infinite shaping time)

25. Result: S/N for 167cm Ladder At shaping time of 3  s; 0.5  m process qualified by GLAST

26. Result: S/N for 132cm Ladder At shaping time of 3  s; 0.5  m process qualified by GLAST 132cm Ladder 300  m Thick

27. Not Yet Considered Inter-Strip Capacitance (under study; typically ~5% pulse sharing between neighboring channels) Leakage Current (small for low-radiation environment) Threshold Variation (typically want some headroom for this!) But overall, 3  s operating point seems quite feasible  proceed to ASIC design!

28. Analog Readout Scheme: Time-Over Threshold (TOT) TOT/   /r TOT given by difference between two solutions to (RC-CR shaper) Digitize with granularity  /n dig

29. Why Time-Over-Threshold? 4 2 6 10 8 TOT/  1011000100 Signal/Threshold = (  /r) -1 100 x min-i With TOT analog readout: Live-time for 100x dynamic range is about 9  With  = 3  s, this leads to a live-time of about 30  s, and a duty cycle of about 1/250  Sufficient for power- cycling!

30. Single-Hit Resolution Design performance assumes 7  m single-hit resolution. What can we really expect? Implement nearest-neighbor clustering algorithm Digitize time-over-threshold response (0.1*  more than adequate to avoid degradation) Explore use of second `readout threshold’ that is set lower than `triggering threshold’; major design implication

31. RMS Gaussian Fit RMS Gaussian Fit Readout Threshold (Fraction of min-i) Trigger Threshold 167cm Ladder 132cm Ladder Resolution With and Without Second (Readout) Threshold

32. Lifestyle Choices Based on simulation results, ASIC design will incorporate: 3  s shaping-time for preamplifier Time-over-threshold analog treatment Dual-discriminator architecture The design of this ASIC is now underway.

33. But Can It Track Charged Particles? 1100.1 Energy (MeV) z (cm) Photon Distributions at R = 25 cm

34. Photon Interactions in Silicon (Thanks to Takashi Maruyama, SLAC)

35. Converted electrons can come out of Si B = 5 Tesla E < 0.1 MeV 0.1 < E < 0.5 MeV 0.5 < E < 1 MeV 1 < E < 10 MeV (Thanks to Takashi Maruyama, SLAC)

36. Photon Conversion Probability 0.11 10 0.1110 Energy (MeV) Edep > 50 keV 60° 75.5° 82.8° 86.4°  (Thanks to Takashi Maruyama, SLAC)

37. No. of Hits 0.1110 Energy (MeV) Edep > 50 keV Normal incident (Thanks to Takashi Maruyama, SLAC)

38. 5 Tesla, Eth > 50 keV3 Tesla, Eth > 50 keV5 Tesla, Eth > 30 keV No. of hits: 68 strips/train 69 strips/train 106 strips/train Occupancy: 0.27% 0.28% 0.42% 25k channels Tracker Layer 1 Simulation Photon flux: 241 photons/4 bunches 5784 photons/train Use 241 photons 1000 times to increase statistics. (Thanks to Takashi Maruyama, SLAC)  Seem tractable at this level.

39. Where Next? We’ve just begun the process of fleshing out the design of this `Gossamer Tracker’ In the 3-year R&D window, we need to: Demonstrate ability to read out long ladders Demonstrate resolution and dynamic range Demonstrate passive cooling (data transmission is an issue!) Develop ultra-light, rigid mechanical systems Demonstrate need for low-mass tracker (central, forward) Prove that such a tracker will perform well in integrated tracking system

40. Some (Very Preliminary) Roles Santa Cruz Develop prototype front-end ASIC Test bench results with `makeshift’ ladder Test-beam studies (S/N and resolution as a function of whatever SLAC Explore occupancy, pattern recognition issues Explore mechanical designs Paris Mechanical/thermal finite element analysis ASIC `Back-end’ architecture Explore mechanical designs

41. Roles (continued) Michigan Interferometric alignment systems New Group? Could begin with simulation… Calorimeter-assisted tracking (Vees, kinks) Track/cluster matching Physics signals Or not… Procurement/construction of more appropriate ladder Test beam preparation and execution Thermal and mechanical systems

42. Summary An ultra-light silicon-strip tracker may well be feasible at a high-energy electron-positron Linear Collider Looks reasonable on paper, but much work must be done over next 3 years to prove the principle, show need An international collaboration (SiLC) is forming to explore this and other silicon-tracking option for the LC Work on `Gossamer’ Tracker currently focussed at SCIPP and SLAC, but we expect this to expand