1 / 35

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.

liang
Télécharger la présentation

Gas-based tracking for SuperBelle

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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.

More Related