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The possibility of improving TOP counter

The possibility of improving TOP counter. Nagoya university Yuji Enari. Introduction. mention about the p /K separation of TOP counter, especially about effect of group velocity of the photon. Definition of Separation. D TOP + D TOF. S =. ・ N ph. s t.

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The possibility of improving TOP counter

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  1. The possibility of improving TOP counter Nagoya university Yuji Enari PID meeging @ Nagoya univ

  2. Introduction • mention about the p/K separation of TOP counter, especially about effect of group velocity of the photon. • Definition of Separation. DTOP + DTOF S = ・ Nph st S1ph = Separation of single photon DTOP,TOF : time difference of pi/K (K-pi) st : Time resolution Nph : Number of detected Photo-electron PID meeging @ Nagoya univ

  3. Time difference DTOP and DTOF TOP counter measures time difference btw p/K TOP TOF DTOP + DTOF = 200ps PID meeging @ Nagoya univ

  4. Uncertainty of TOP measurement.  If we choose to use bar-TOP, this effect is negligible. PID meeging @ Nagoya univ

  5. The chromatic effect. The chromatic effect consists of 2 component. a.Cherenkov angle Determined by the reflective index b. Light velocity Determined by ‘Group’ index These two contribution work oppositely. a :b = -1 : 2  schromatic (1/n・Dn) b. Dl a. PID meeging @ Nagoya univ

  6. The measurement of TOP resolution • From the Beam test result. • With improved polishing accuracy of the quartz bar. • This result is limited by chromatic effect (at large L).  Estimate pi/K separability in the Belle detector PID meeging @ Nagoya univ

  7. TOP difference and Nph in Belle detector P = 3.5GeV/c, barthick = 20mm 30° 45° 60° 90° 120° 140° DTOP : -3.6 -1.4 14.6 110.0 14.62.7 DTOF : 62.6 44.236.1 31.3 36.1 40.84 Nph : ～90 ～60 ～40 ～30 ～40～65 PID meeging @ Nagoya univ

  8. Expected TOP counter’s performance in Belle. • Separation of single photo-electron and S lmean = 390nm, stts = 75ps 30 45 60 90 140 Number of detected photon S S1ph Hard to separate p/K around qin = 45, p=3.5GeV/c region. PID meeging @ Nagoya univ

  9. How we can do? • Increase photon statistics • Use High Q.E. material (Ga・As or APD?) • Use thicker quartz bar. (20mm  40mm) • Improve time resolution. • Use long wave length region (Dn get small) • (and) use good photon detector(T.T.S < 50ps) PID meeging @ Nagoya univ

  10. Correlation between TTS and wave length. P = 3.5GeV/c, in Belle system Separation of single photo-electron stts = 100ps stts = 50ps S1ph S=3 S=5.5  We have to use long wave length with stts < 50 ps. PID meeging @ Nagoya univ

  11. wave length : lpeak = 490nm with high Q.E.(20%@lpeak) time resolution : stts=50ps barthick = 20mm barthick = 40mm PID meeging @ Nagoya univ

  12. Summary • The chromatic effect make the largest uncertainty. • To get good performance in Belle system, • Measure long wave length region. • Use good Photon detector which has TTS of 50 ps. • Need good Q.E. material.(Q.E.×C.E.>２０％?) • Workable in 1.5T magnetic field  Photon detector R&D is very very important. PID meeging @ Nagoya univ

  13. Silicon Photo-Multiplier PID meeging @ Nagoya univ

  14. What’s SiPM • SiPM • a kind of multi pixel Avalanche Photo Diode. • Operate in limited Geiger mode. pixel size : 42 ×42 mm2 • Merit? • Available in magnetic field. • High Q.E. at long wave length (very attractive for TOP counter) , • High gain. • Good time resolution Etc.etc. PID meeging @ Nagoya univ

  15. Geiger-mode Avalanche photo diode • Limited Geiger-mode in SiPM • Under bias voltage of 10-20% more than break down voltage. • Geiger discharge is stopped when bias goes down below b.d. voltage. • Gain : • Qpixel = Cpixel・(Vbias – Vbeakdown) • Cpixel  100fF  Qpixel  100pC Vbias ～　５０V All pixel(576pixel) are connected by common Al strip.  each pixel operates as a binary device, works as an analogue detector. Close up view of pixel PID meeging @ Nagoya univ

  16. Performance of SiPM • Pulse shape • Gain • Linearity and dynamic range. • Detection efficiency • Noise – temperature dependence. • Time resolution PID meeging @ Nagoya univ

  17. pulse height spectra SiPM has good energy resolution as long as 2 photons enter in same pixel. PID meeging @ Nagoya univ

  18. Detection efficiency PID meeging @ Nagoya univ

  19. Noise PID meeging @ Nagoya univ

  20. Time resolution s ～ 50ps PID meeging @ Nagoya univ

  21. Comparison to another detector PID meeging @ Nagoya univ

  22. Summary • SiPM is very good application for TOP counter. • High Q.E. High gain, single photon sensitive. • Good timing resolution. • Workable in strong magnetic field of 1.5T. • To be use in TOP counter… • Size. (1mm2 20mm ×200mm?) • Enlarge the effective area in each pixel. (e = 0.3  0.5) • Noise PID meeging @ Nagoya univ

  23. Reference 1, B.Dolgoshein (Moscow Engineering and Physics Institute) - An Advanced study of Silicon Photomultiplier ICFA instrumentation Bulletin - The silicon photomultiplier and its possible application transparency of 3rd BEAUNE conference and its proceeding PID meeging @ Nagoya univ

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