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

2. 21/12/99Ian C. Brock2 Outline 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 STT Group: Bonn, Freiburg (Germany) MEPhI (Russia) York, Toronto (Canada) ANL (USA) Tel Aviv (Israel) Help from HH1, DESY, McGill, MSU, Penn State

3. 21/12/99Ian C. Brock3 HERA 920 GeV protons 27.5 GeV electrons or positrons

4. 21/12/99Ian C. Brock4 HERA Luminosity Upgrade Luminosity now 30-40 pb -1 per year After upgrade  150 pb -1 per year  Large statistics at high Q 2 Longitudinal electron/positron beam polarization  Electroweak studies

5. 21/12/99Ian C. Brock5 ZEUS Experiment Asymmetric beam energies  asymmetric detector High track density in forward (proton) direction High Q 2 Neutral Current event

6. 21/12/99Ian C. Brock6 NC Events at High Q 2 Q 2 > 5000 GeV 2  2000 events/year after lumi upgrade Need reliable, efficient tracking in forward direction Any heavy object mostly has decay products in forward region

7. 21/12/99Ian C. Brock7 CC Events at High Q 2 Q 2 > 5000 GeV 2 Vertex finding needed to reconstruct  had Kinematic reconstruction can only use hadronic variables

8. 21/12/99Ian C. Brock8 NC and CC Events at High Q 2 High Q 2, high x, low y (  had < 14 0 ) Find z position of vertex Improve reconstruction of kinematic variables

9. 21/12/99Ian C. Brock9 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 = m D* - m D  1 MeV Pseudorapidity  = -ln (tan  /2)  = 1.75   = 20 0  = 3   = 6 0

10. 21/12/99Ian C. Brock10 Vector Mesons Extend W,  range e.g.  Mesons Q 2 > 10 GeV 2 1.75 <  < 3.1  M  40 MeV Information on gluon density QCD Effects

11. 21/12/99Ian C. Brock11 Forward Tracking at High Luminosity 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

12. 21/12/99Ian C. Brock12 FDET in ZEUS Tracking Detectors: CTD for  > 25 0 CTD+FTD for 14 0 <  < 25 0 FTD only for  < 14 0 FDET consists of: FTD for tracking – 3 chambers 3 layers per chamber 6 wires per cell in z Cells 25 mm high, up to 1.5 m long TRD for e/  separation 2  30 GeV

13. 21/12/99Ian C. Brock13 The Planar Drift Chambers (FTD) 912 Cells with 5472 signal wires

14. 21/12/99Ian C. Brock14 Current FDET Limitations Large cell size  high occupancy Segment finding efficiency (was  65%) now  75%, Lots of fake segments (Segment = Track element in 1 FTD chamber) Monte Carlo CC events Q 2 > 5000 GeV 2

15. 21/12/99Ian C. Brock15 Improving FDET Geometry Average occupancy  5% 10-15% straws have more than 1 hit Occupancy is reasonably flat vs.  Numbers almost same for Q 2 > 100 GeV 2 and Q 2 > 10000 GeV 2

16. 21/12/99Ian C. Brock16 STT Occupancy Occupancy near beam- pipe strongly affected by new magnets Much better than current FTDs, but still not small!

17. 21/12/99Ian C. Brock17 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 6 0 to 24 0 Full azimuthal coverage

18. 21/12/99Ian C. Brock18 Straws 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

19. 21/12/99Ian C. Brock19 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)

20. 21/12/99Ian C. Brock20 Picture of Straw End-plugs Close-up view of a sector, with end-plugs, wire fixations and ground strips

21. 21/12/99Ian C. Brock21 HV and Signal Front-End Electronics 470 k  HV Source Straw HV Fuse 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)

22. 21/12/99Ian C. Brock22 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

23. 21/12/99Ian C. Brock23 An STT Sector in Production Wiring in York, Canada DESY, Germany (Bonn, HH1 manpower) Freiburg, Germany MEPhI, Russia

24. 21/12/99Ian C. Brock24 Signal Calibration All straws checked with 55 Fe source 10 channels from test array all within ±5% variation

25. 21/12/99Ian C. Brock25 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

26. 21/12/99Ian C. Brock26 Electronics Use as much existing electronics as possible TRD has 2000 channels STT has 11000 channels è Multiplexing needed Would also like to have dE/dx 2 possible chips ASDBLR: preamp, shaper, 2 comparator levels dE/dx possible Xe/CO 2 gas mixture ASDQ preamp, shaper, 1 comparator level drift time only Ar/CO 2 or Xe/CO 2 gas mixture

27. 21/12/99Ian C. Brock27 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

28. 21/12/99Ian C. Brock28 Multiplexing Scheme 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

29. 21/12/99Ian C. Brock29 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

30. 21/12/99Ian C. Brock30 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/CO 2 gas mixture Efficiency  95%

31. 21/12/99Ian C. Brock31 Pattern Finding in STT Concept exists for 3-D pattern finding First version using histogram method developed Evaluation procedure exists

32. 21/12/99Ian C. Brock32 10 Tracks in STT

33. 21/12/99Ian C. Brock33 Tight Jet Simulated jet 4 tracks in a cone of 3 0 Efficiency close to 90% Hope for further improvement with 3-D pattern finding

34. 21/12/99Ian C. Brock34 Combining STT with MVD and CTD 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 CTD VCTRAK Use to look for matching hits in MVD New Use to pick up correct hits in FTDs TFRECON

35. 21/12/99Ian C. Brock35 Expected Resolutions STT for MVDSTT with MVD  z  1 mm

36. 21/12/99Ian C. Brock36 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 startedAug 1999 Wiring of proper sectors startedOct 1999 Prototype multiplexing electronicsOct 1999 Aim to finish wiring Mar-Apr 2000 Electronics ready for mounting June 2000 Mount STT in FDET Oct 2000

37. 21/12/99Ian C. Brock37 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