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Equipping ZEUS for the New Millennium The ZEUS Straw-Tube Tracker

Equipping ZEUS for the New Millennium The ZEUS Straw-Tube Tracker. Obers eminar zur Physik am Elektron-Proton Speicherring Freiburg Univerisity 21 December 1999 Ian C. Brock Bonn University. Outline. STT Group: Bonn, Freiburg (Germany) MEPhI (Russia) York, Toronto (Canada) ANL (USA)

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Equipping ZEUS for the New Millennium The ZEUS Straw-Tube Tracker

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  1. Equipping ZEUS for the New MillenniumThe ZEUS Straw-Tube Tracker Oberseminar zur Physik am Elektron-Proton Speicherring Freiburg Univerisity 21 December 1999 Ian C. Brock Bonn University

  2. Outline STT Group: Bonn, Freiburg (Germany) MEPhI (Russia) York, Toronto (Canada) ANL (USA) Tel Aviv (Israel) Help from HH1, DESY, McGill, MSU, Penn State • HERA and ZEUS • Physics Reasons for Improved ZEUS Tracking • Current ZEUS Forward Detector • Straw tubes • Implementation in ZEUS • STT Production • Test-beam • Track Finding • Conclusions Ian C. Brock

  3. HERA • 920 GeV protons • 27.5 GeV electrons or positrons Ian C. Brock

  4. HERA Luminosity Upgrade • Luminosity now 30-40 pb-1 per year • After upgrade 150 pb-1 per year Large statistics at high Q2 • Longitudinal electron/positron beam polarization Electroweak studies Ian C. Brock

  5. ZEUS Experiment Asymmetric beam energies  asymmetric detector High Q2 Neutral Current event High track density in forward (proton) direction Ian C. Brock

  6. NC Events at High Q2 • Q2 > 5000 GeV2 • 2000 events/year after lumi upgrade • Need reliable, efficient tracking in forward direction • Any heavy object mostly has decay products in forward region Ian C. Brock

  7. CC Events at High Q2 • Q2 > 5000 GeV2 • Vertex finding needed to reconstruct had • Kinematic reconstruction can only use hadronic variables Ian C. Brock

  8. NC and CC Events at High Q2 • High Q2, high x, low y(had < 140) • Find z position of vertex • Improve reconstruction of kinematic variables Ian C. Brock

  9. Charm (+ Bottom) • Use tracks up to  = 3.0( = 1.75 at present) • Important for b and c events • e.g. 1.75 <  < 3.0M = mD* - mD  1 MeV • Pseudorapidity = -ln (tan/2) • = 1.75   = 200  = 3   = 60 Ian C. Brock

  10. Vector Mesons • Extend W, range • e.g.  MesonsQ2 > 10 GeV21.75 <  < 3.1M 40 MeV • Information on gluon density • QCD Effects Ian C. Brock

  11. Environment High track density Highest close to beam axis Large and variable backgrounds Solutions Large number of wires Shortest cells where occupancy highest Robust construction 4 views instead of 3 If necessary, sacrifice particle ID for track finding Forward Tracking at High Luminosity Ian C. Brock

  12. FDET in ZEUS • Tracking Detectors: • CTD for q > 250 • CTD+FTD for 140< q < 250 • FTD only for  < 140 • FDET consists of: • FTD for tracking – 3 chambers3 layers per chamber6 wires per cell in zCells 25 mm high, up to 1.5 m long • TRD for e/ separation 230 GeV Ian C. Brock

  13. The Planar Drift Chambers (FTD) 912 Cells with 5472 signal wires Ian C. Brock

  14. Current FDET Limitations Monte Carlo CC eventsQ2 > 5000 GeV2 • Large cell size  high occupancy • Segment finding efficiency (was 65%) now 75%, • Lots of fake segments (Segment = Track element in 1 FTD chamber) Ian C. Brock

  15. Improving FDET Geometry • Average occupancy5% • 10-15% straws have more than 1 hit • Occupancy is reasonably flat vs.  • Numbers almost same for Q2 > 100 GeV2 andQ2 > 10000 GeV2 Ian C. Brock

  16. STT Occupancy • Occupancy near beam-pipe strongly affected by new magnets • Much better than current FTDs,but still not small! Ian C. Brock

  17. Detector Concept • 2 gaps of 208 mm available • TRD gas system and read-out electronics available • 4 super-layers per gap,each consisting of 3 layers of straws • Polar angles from 60 to 240 • Full azimuthal coverage Ian C. Brock

  18. Made of 2 layers of 50 m kapton foil Coated with 0.2 m Al, 4 m C, 3-4m polyurethane Cut into1cm strips Wound into 7.5 mm diameter straws Use knowledge acquired by MEPhI Straw tube tracker (with TR) developed for HERA-B and ATLAS Good radiation hardness Straws Ian C. Brock

  19. Straw Assembly • Each straw fitted with end-plugs • End-plug consists of • wire fixation • polycarbonate insert • Cu strip for ground contact • Wire or resistor for HV/signal • Wire is 50 m Cu-Be (easy to solder) Ian C. Brock

  20. Picture of Straw End-plugs Close-up viewof a sector,with end-plugs,wire fixationsand ground strips Ian C. Brock

  21. HV and Signal 470 k HV Fuse Front-End Electronics HV Source Straw Fuses should blow when current of >2 mA flows for short time Do not blow when chamber trips due to background Need current limited power supply for normal operation(1-10 A) Ian C. Brock

  22. STT Sector • Two sizes -- 194 or 266 straws – glued as 3-layer arrays • Straw positions in array had r.m.s. of 55 m in prototype sector • After wiring array glued into a C-fibre box • Mechanical precision of box and array position in box 200 m • Box covered with 17m Cu foil for screening Ian C. Brock

  23. An STT Sector in Production Wiring in York, Canada DESY, Germany (Bonn, HH1 manpower) Freiburg, Germany MEPhI, Russia Ian C. Brock

  24. Signal Calibration All straws checked with 55Fe source 10 channels from test array all within ±5% variation Ian C. Brock

  25. From Sectors to a Detector • Central 12 mm honeycomb plate to support sectors • Al strips round rim for attachment to conical ring • Mount front-end electronics on sector • Mount cable driver electronics on rim for ease of cooling and access • Assembly of electronics and sectors on support plate at DESY Ian C. Brock

  26. Use as much existing electronics as possible TRD has 2000 channels STT has 11000 channels Multiplexing needed Would also like to have dE/dx 2 possible chips ASDBLR: preamp, shaper, 2 comparator levels dE/dx possible Xe/CO2 gas mixture ASDQ preamp, shaper,1 comparator level drift time only Ar/CO2 or Xe/CO2 gas mixture Electronics Ian C. Brock

  27. Overall Electronics Concept • Front-end is new • Receiver/postamps not needed • FADC and rest of readout kept from TRD • Readout window increased from 80 to 128 time bins Ian C. Brock

  28. Original scheme foresaw applying different gains to each channel Cable too slow and has memory!(photos) New scheme Use 200 ns time delays between 6 successive straws CMOS one-shots used for delay Input & Output 0 or 1 No dE/dx possible Multiplexing Scheme Ian C. Brock

  29. Multiplexing Scheme • Prototype multiplexing scheme ready in October • Tested in lab (ANL) and works as expected • Now mounted on prototype sector for testing in DESY test-beam • ASDQ chips ordered • Tel Aviv will fabricate cable drivers Ian C. Brock

  30. Test Beam • Prototype detector ran in test beam with ASDBLR chip, but no multiplexing • Worked well, but shielding is important • Same detector with multiplexing electronics currently in beam • Want to freeze electronics design in January Xe/CO2 gas mixture Efficiency 95% Ian C. Brock

  31. Pattern Finding in STT • Concept exists for 3-D pattern finding • First version using histogram method developed • Evaluation procedure exists Ian C. Brock

  32. 10 Tracks in STT Ian C. Brock

  33. Tight Jet • Simulated jet • 4 tracks in a cone of 30 • Efficiency close to 90% • Hope for further improvement with 3-D pattern finding Ian C. Brock

  34. STT should provide track elements at some z (CTD endplate) with track parameters and covariance matrix MVD consists of single-sided silicon Barrel: 3, 3 z layers Wheels: 4, each with 2 layers Use as starting point for track finding in CTDVCTRAK Use to look for matching hits in MVDNew Use to pick up correct hits in FTDsTFRECON Combining STT with MVD and CTD Ian C. Brock

  35. Expected Resolutions STT for MVD STT with MVD z  1 mm Ian C. Brock

  36. Timetable • First proposal in Jan 1998 • Submitted to PRC and approved July 1998 • Prototype sector ready Dec 1998 • Production of full detector started Mar 1999 • Wiring of test mini-sectors started Aug 1999 • Wiring of proper sectors started Oct 1999 • Prototype multiplexing electronics Oct 1999 • Aim to finish wiring Mar-Apr 2000 • Electronics ready for mounting June 2000 • Mount STT in FDETOct 2000 Ian C. Brock

  37. Conclusions • STT(+ MVD) should provide a substantial improvement to (forward) tracking in ZEUS • Funding for project is secured • Looking forward to first few complete sectors before Christmas! • Need to verify performance of electronics in test beam • Ready for HERA shutdown 1 May or 1 Sept 2000 Ian C. Brock

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