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Gas-based tracking for SuperBelle

Gas-based tracking for SuperBelle. Beam background Upgrade plan Summary. Shoji Uno (KEK) April, 20-22, 2005 2 nd Joint Super B factory WS in Hawaii. Wire chamber. Wire chamber is a good device for the central tracker.

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Gas-based tracking for SuperBelle

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  1. Gas-based tracking for SuperBelle • Beam background • Upgrade plan • Summary Shoji Uno (KEK) April, 20-22, 2005 2nd Joint Super B factory WS in Hawaii

  2. Wire chamber • Wire chamber is a good device for the central tracker. • Less material  Good momentum resolution. • Cheap  It is easy to cover a large region. • Established technology  Easy construction. • Many layers  Provide trigger signals and particle ID information. • Wire chamber can survive at Super-KEKB. • Our answer does not change after the last WS in 2004. • The beam background became smaller even for higher beam current and higher luminosity. • We recognize the luminosity term is small, clearly.

  3. CDC Total Current • Maximum current is still below 1.2mA, even for higher stored current and higher luminosity. • Vacuum condition is still improving. • Thanks KEKB people for hard work. • I hope there is still room to improve vacuum condition further.

  4. Hit rate Apr.-5th ,2005 IHER = 1.24A ILER = 1.7A Lpeak = 1.5x1034cm-2sec-1 ICDC = 1mA Small cell Inner Main 10KHz

  5. Luminosity Dependences Feb, 2004 CDC BG did not change! Inner most Middle Outer

  6. Hit rate at layer 35 Dec.,2003 LER HER IHER = 4.1A Hit rate = 13kHz ILER = 9.4A Hit rate = 70kHz Dec., 2003 : ~5kHz Now : ~4kHz In total 83kHz

  7. Simulation Study for Higher Beam Background Detail was reported in the last WS by K.Senyo. MC +BGx1 MC+BGx20

  8. Tracking eff. with Bp+p- decays With 600ns dead time and under x20 occupancy, CDC keeps about 90% of the single tracking efficiency including geometrical acceptance. (thus the tracking itself has almost 100% eff.) B->pp reconstruction eff. including geometrical acceptance Square root of recon. eff. of the left ~ single track efficiency of mid/high p Occupancy Overlay(times) Occupancy Overlay(times)

  9. Slow p efficiency from BD*(Dpslow)p • About 80% of efficiency is kept in the slow p efficiency under x20 occupancy. • Reconstruction using SVD information is necessary to recover the loss of efficiency. recon. eff. of the slow pion ~ single track efficiency of slow p BD*p reconstruction eff. including geometrical acceptance

  10. Occupancy Random trigger x20 Bkgd in Belle CDC ~ x3 Bkgd in Babar DCH

  11. at HL6 in KEK

  12. Idea for upgrade • In order to reduce occupancy, • Smaller cell size • A new small cell drift chamber was constructed and installed. • It has been working, well. • Faster drift velocity • One candidate : 100% CH4 • Results show worse spatial resolution due to a large Lorentz angle. • A beam test was carried out under 1.5T magnetic field. • So far, no other good candidate.

  13. XT Curve & Max. Drift Time Normal cell(17.3mm) Small cell(5.4mm)

  14. Baseline design CDC SVD

  15. Main parameters

  16. Wire configuration • 9 super-layers : 5 axial + 4 stereo(2U+2V) • A 160*8, U 160*6, A 192*6, V 224*6, • A 256*6, U 288*6, A 320*6, V 352*6, A 388*8 • Number of layers : 58 • Number of total sense wires : 15104 • Number of total wires : ~60000

  17. Deformation of endplate • Number of wires increase by factor 2. • Larger deformation of endplate is expected. • It may cause troubles in a wire stringing process and other occasions. • Number of holes increases, but a chamber radius also enlarges. Cell size is changing as a function of radius to reduce number of wires. • The fraction of holes respect to total area is not so different, as comparing with the present CDC. • 11.7% for present CDC • 12.6% for Super-Belle CDC • In order to reduce deformation of endplates, • The endplate with a different shape is considered. • Wire tension of field wires will be reduced. • Anyway, we can arrange the wire configuration and can make a thin aluminum endplate.

  18. Better background • Higher luminosity is not always higher beam background. • KEKB Luminosity > PEPII Luminosity • Belle background < Babar background • Now, we(KEKB-Belle+PEPII-Babar) are discussing a future machine. New machine should be designed to reduce the beam background based on our knowledge. • We should make effort to get better background condition in the future machine using present both machines and both detectors.

  19. Smaller background in Babar CDC • Only ~0.3% occupancy for LER particle background. Occupancy normalized by readout time window(%) Brian Petersen’s talk in HL6

  20. Bestcondition • Small SR background (PEPII HER) + Small HER particle background (KEKB HER) + Small LER particle background (PEPII LER) + Small Luminosity term (KEKB) + Movable masks (KEKB) • Small pixel or striplet (New) + Larger SVD (Babar SVT) + Larger gas-based CDC (Belle CDC) + FADC readout (Babar CDC) + Good reconstruction software (Babar?) + Lower B field?

  21. Summary • Our conclusion does not change from the previous WS in the last year. • Background became better even for higher stored current and higher luminosity. • We recognize the luminosity term is small, clearly. • New CDC • Smaller cell size for inner most layers. • Larger outer radius • Better performance is expected. • Or lower magnetic field.

  22. Radiation Damage Test Gain degradation Total accumulated charge on sense wire(C/cm) a: ’93 Plastic tube d: ’94 SUS tube b: ’93 Plastic tube + O2 filter e: ’94 SUS tube + O2 filter c: ’94 Plastic tube f: ’94 Plastic tube

  23. Momentum Resolution • Thanks for filling He based gas and using Aluminum field wires. • The resolution was calculated using cosmic ray events during a normal physics run. • BaBar data was obtained from a talk in Vancouver WS.

  24. Momentum Resolution • We could obtain a small constant term using He-based gas and aluminum field wires. • Slop parameter is not so good as compared with expected value. • We had to change the electronics parameters to reduce the cross talk. • HV is slightly lower than the original value. • Alignment is not perfect. • More tuning to reject bad points. • Some effects from the beam background. Transverse Momentum(GeV/c)

  25. Bhabha Mu pair M.I.P in Hadronic events 0.35<P<0.88GeV/c without any PID. Electron dE/dx Resolution • Good resolution was obtained. • It is useful to identify hadrons and electrons.

  26. dE/dx Measurement • MQT chip (Charge to Time conversion) and multi-hit TDC. • 80% truncated mean. • Relativistic rise. • 1.4 for electron. • Good PID performance for lower momentum region. • dE/dx information helps to separate high momentum K/p. Normalized dE/dx log10P(GeV/c)

  27. Comparison with Babar • Momemtum resolution(SVD+CDC) • sPt/Pt = 0.19Pt  0.30/b[%] : Belle • sPt/Pt = 0.13Pt + 0.45 [%] : BaBar • Mass(dE) resolution • Mass resolution for inclusive J/y  m+m- • 9.6 MeV(Belle) vs 12.3 MeV(BaBar) • dE resolution for B0 D-p+, D- K+p-p- • 13.8MeV(Belle) vs 19.0MeV(BaBar) • We could obtain better resolution than BaBar. • BaBar has a CFRP support cylinder with 2mm thickness between SVD and CDC. • Tracking efficiency for low momemtum particles is worse than BaBar. • D*+D*-yield(slow p eff.) ~0.5(?) x BaBar • 3 layers SVD (Belle) vs 5 layers SVD(BaBar) • Energy loss measurement • 5.6%(Belle)vs 7%(Babar) for Bhabar events

  28. Change of bias voltage for preamp Replacing with new S/QT for layer 0 & 1 Installation of small cell chamber 2000 Summer 2001 Summer 2002 Summer 20003 Summer 2004 Summer Pulse height variation Hokuue

  29. Hit rate Apr.-5th , 2005 IHER = 1.24A ILER = 1.7A Lpeak = 1.5x1034 ICDC = 1mA Small cell Inner Main 10kHz

  30. Small Cell Drift Chamber

  31. Photo of small cell chamber Just after wire stringing Installation in 2003 summer

  32. Curved Endplate • Deformation of endplate due to wire tension was calculated at design stage of present Belle CDC. Deformation(mm) 35.2 2.03 1.31 Present New

  33. Expected performance • Occupancy • Hit rate : ~140kHz  ~7Hz X 20 • Maximum drift time : 80-300nsec • Occupancy : 1-4% 140kHz X 80-300nsec = 0.01-0.04 • Momemtum resolution(SVD+CDC) • sPt/Pt = 0.19Pt  0.30/b[%] : Conservative • sPt/Pt = 0.11Pt  0.30/b[%] : Possible  0.19*(863/1118)2 • Energy loss measurement • 6.9% : Conservative • 6.4% : Possible  6.9*(752/869)1/2

  34. D12 D9 D3 D6 Movable Masks • 16 masks in HER and 16 masks in LER. • 8 horizontal + 8 vertical for each rings. • Location • 4(H)+4(V) at D6 and 4(H)+4(V) at D3 for LER • 4(H)+4(V) at D9 and 4(H)+4(V) at D12 for HER

  35. Effectiveness • Usually, the horizontal masks are not effective. Because the horizontal tail is not so large. • A few vertical masks are quite effective to reduce the beam background in the both cases for storage and injection and also for LER and HER. • By factor two or more. • KEKB had movable masks near IR, which were not so effective to reduce the beam background. • Those masks in both of LER and HER were removed.

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