The Gossamer Tracker: A Novel Concept for a LC Central Tracker

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. Fall 2001 recommendation of the High Energy Physics Advisory Panel (HEPAP) to the Department of Energy’s Office of Science: “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.” 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 Diagrams: Wolfgang Killian, Karlsruhe This physics will be produced via the t-channel  will tend to be forward Absent Higgs Sector, something else must act to renormalize W couplings

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) Rmax = 190cm 3 T Field Conventional (Pb/Sci) Calorimeter S Design: Solid-State Tracking Rmax = 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% X0 per layer) at low and intermediate mo-mentum Code: http://www.slac.stanford.edu/~schumm/lcdtrk.tar.gz

12. Idea: Noise vs. Shaping Time Agilent 0.5 mm CMOS process (qualified by GLAST) Min-i for 300mm Si is about 24,000 electrons

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

17. Helsinki Obninsk Karlsruhe Paris Prague Wien Geneve Torino Pisa Rome Barcelona Valencia The SiLC Collaboration Brookhaven Ann Arbor Wayne Santa Cruz USA Europe Korean Universities Seoul &Taegu Tokyo 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. Post-Doc Gavin Nesom (half-time LC postdoc from 1999 program) Student Christian Flacco (will do BaBar thesis) Faculty/Senior Alex Grillo Hartmut Sadrozinski Bruce Schumm Abe Seiden The SCIPP/UCSC Effort 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 t0 reflects instantaneous expansion of hole cloud due to space-charge repulsion. Diffusion constant given by mh = hole mobility Reference: E. Belau et al., NIM 214, p253 (1983)

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 3ms; 0.5 mm process qualified by GLAST

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

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 given by difference between two solutions to TOT/t (RC-CR shaper) q/r Digitize with granularity t/ndig

29. 10 8 6 TOT/ 4 2 Why Time-Over-Threshold? 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! 100 x min-i 1 10 100 1000 Signal/Threshold = (/r)-1

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

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. Energy (MeV) 0.1 1 10 But Can It Track Charged Particles? Photon Distributions at R = 25 cm z (cm)

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

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

36. (Thanks to Takashi Maruyama, SLAC) Photon Conversion Probability  86.4° Edep > 50 keV 82.8° 75.5° 60° 10 0.1 1 0.1 1 10 Energy (MeV) Energy (MeV)

37. (Thanks to Takashi Maruyama, SLAC) No. of Hits Normal incident Edep > 50 keV 0.1 1 10 Energy (MeV)

38. 5 Tesla, Eth > 50 keV 3 Tesla, Eth > 50 keV 5 Tesla, Eth > 30 keV Photon flux: 241 photons/4 bunches 5784 photons/train Use 241 photons 1000 times to increase statistics. (Thanks to Takashi Maruyama, SLAC) Tracker Layer 1 Simulation No. of hits: 68 strips/train 69 strips/train 106 strips/train Occupancy: 0.27% 0.28% 0.42% 25k channels  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. 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 Some (Very Preliminary) Roles

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