1. PID Upgrade for Super-KEKB / Belle
BESS-Belle-CLEO-BaBar
2007 Joint Workshop on Charm Physics
PID Upgrade for Super-KEKB / Belle
Toru Iijima
Nagoya University
November 27, 2007

2. Toru Iijima, BBCB2007 @ IHEP, Beijing
Contents
Introduction
Quartz-based RICH
Time-Of-Propagation Counter
Aerogel-based RICH
Proximity Focusing Aerogel RICH
Summary
Appology;
I cannot cover all the proposed idea, developments
for (genric) super-B.
2007/11/27
Toru Iijima, IHEP, Beijing

3. Super-Belle PID (an option)
To cope with increased background (present x ~20)
To improve the performance.
Target: > 4s at 4 GeV/c
Novel Ring Imaging Cherenkov Counters
w/ advanced radiator & photo-detection technologies e-
8.0GeV e+
3.5GeV
2.6m
1.2m
1.5T
TOP Counter
Aerogel-RICH
Tight space limitation
Barrel: DR = 10-20cm
Endcap: DZ = 28cm
There are also other options: Focusing-DIRC, TOF.
2007/11/27
Toru Iijima, IHEP, Beijing

4. Key Technology: Radiators
Interferogram
Quartz (fused Silica)
Accurately polished to preserve the Cherenkov angle info. after many internal reflections.
Polish: 0.5nm
Figure: 0.6mm
Squareness: ±0.3mrad
Silica aerogel
Improved transmission by new recipie.
LT > 40mm for n=
Hydrophobic for long term stability
Refractive index
Transmssion length ◆
▲2004
■Before 2003
Transmission length at  = 400nm
2007/11/27
Toru Iijima, IHEP, Beijing

5. Key Technology: Photodetectors
High gain, Q.E., C.E.
Good time resolution
Good effective area
in magnetic field (1.5T)
MCP-PMT
Micro-channel-plate PMT
HAPD
Hybrid Avalanche Photodiode
Geigermode-APD
PMT
MCP-PMT
HPD / HAPD
Geigermode-APD
Gain
>106
～106
～103
X10～100 w/ APD
Quantum Eff.
～20%, ～400nm (bialkali)
> 50%, ～600nm
Collection Eff.
70%
60%
100%
50%
Time resolution
～300ps
～30ps
～150ps
Depends on readout
<100ps
To be checked
B-field immunity ×
△ Depends on angle ○
Problems
lifetime
Noise, size
2007/11/27
Toru Iijima, IHEP, Beijing

6. Time-Of-Propagation Counter
Accurately polished quartz & precision timing
2007/11/27
Toru Iijima, IHEP, Beijing

7. Toru Iijima, BBCB2007 @ IHEP, Beijing
Quartz based RICH
Use of total internal reflection in
accurately polished quartz bar.
A concept was invented by B.Ratcliff et al.
DIRC (Detector of Internally Reflected Cherenkov light)
NIM A479(2002)1
TOP (Time Of Propagation) Counter
NIM A453(2000)331
Focusing DIRC/TOP
(X, Y)
(X, TOP)
(X, Y, TOP)
TOP or
Measurement coordinates
2007/11/27
Toru Iijima, IHEP, Beijing

8. Toru Iijima, BBCB2007 @ IHEP, Beijing
TOP counter
Simulation
2GeV/c, q=90 deg.
Cherenkov ring imaging using timing information
Difference of path length
 Difference of time of propagation (TOP)
150~200ps from TOP + TOF from IP
with precise time resolution (s~40ps) for each photon
d-ray,
had. int.
2007/11/27
Toru Iijima, IHEP, Beijing

9. Design Quartz: 255cmL x 40cmW x 2cmT Cut at 47.8deg.
to reduce chromatic dispersion
Multi-anode MCP-PMT
Good time resolution (<~40ps), Linear array (5mm pitch)
Three readout planes
MCP-PMT
2007/11/27
Toru Iijima, IHEP, Beijing

10. Toru Iijima, BBCB2007 @ IHEP, Beijing
1x4 MCP-PMT (SL10)
1x4 linear-anode MCP-PMT for TOP readout.
Developed under collab. with Hamamatsu Photonics.
#MCP stage 2
Gain (HV)
2x106 (-3.5KV)
MCP hole dia.
10mm
Geometrical collection eff.
50%
#pixel /size
1x4 / 5mmx22mm
Effective area/
Total area
64%
Confirmed gain > 106 & TTS=30ps(s) in B=1.5T magnetic field.
2007/11/27
Toru Iijima, IHEP, Beijing

11. Toru Iijima, BBCB2007 @ IHEP, Beijing
Chromatic Dispersion
Variation of propagation velocity depending on the wavelength of Cherenkov photons
Light propagation velocity inside quartz
GaAsP photo-cathode ( alkali p.c.)
Higher quantum-efficiency
at longer wavelength → less chromatic error
Photon sensitivity at longer wavelength shows the smaller velocity fluctuation.
2007/11/27
Toru Iijima, IHEP, Beijing

12. Toru Iijima, BBCB2007 @ IHEP, Beijing
Target structure
GaAsP MCP-PMT
GaAsP photocathode
w/ Al protection layer
2 MCP layers with f=10mm hole
Wave form, ADC and TDC distributions for single photon
Enough gain to detect single photo-electron
Good time resolution (TTS=35ps) for single p.e.
pedestal
single photon peak
Gain～
0.64×106
Single p.e.
0.5ns/div
20mV/div
TTS～35ps
2007/11/27
Toru Iijima, IHEP, Beijing

13. Performance with GaAsP
K/p separation power
GaAsP photo-cathode + >400nm filter, CE=36%
3.5s K/p for 4 GeV/c, q=70ﾟ
2007/11/27
Toru Iijima, IHEP, Beijing

14. Toru Iijima, BBCB2007 @ IHEP, Beijing
Focusing TOP
Remaining chromatic effect makes ~100ps fluctuation for TOP.
Use l dependence of Cherenkov angle to correct chromaticity
 Focusing system to measure qc
l  qc  y position
Reconstruct ring image from 3D informations (time, x and y).
Mirror image
Rotate PMT
Focus Mirror
Side view
2007/11/27
Toru Iijima, IHEP, Beijing

15. Performance of Focusing TOP
K/p separation power
GaAsP photo-cathode(+>400mm filter), CE=36%
4.3s separation for 4GeV/c
2007/11/27

16. Proximity Focusing Aerogel RICH
Highly transparent aerogel + Photon Imaging
2007/11/27
Toru Iijima, IHEP, Beijing

17. Proximity Focusing Aerogel RICH
Aerogel radiator (n~1.05, ~2cm) + photodetector (Dx ~ 5mm)
Proximity focusing geometry
No mirror complex.
Suitable for collider and space experiments.
>4s K/p for 0.7 < p < 4.5 GeV/c
@ 4GeV/c, q(p)=310mrad.
q(p)-q(K)=23mrad.
Distance between aerogel to photodetector = 200mm.
Track Incident angles = 17-34deg.
2007/11/27
Toru Iijima, IHEP, Beijing

18. Beam Test w/ Flat Panel PMT
NIM A521(2004) 367
Beam Test w/ Flat Panel PMT
4×4 array of H8500
52.5mm pitch  84% effecive area.
1024 channel
Two MWPC for tracking
Typical Results
s0 = 14.8 mrad.
<Npe> = 6.2
4s K/p
@ 4GeV/c
Want more photons !
2007/11/27
Toru Iijima, IHEP, Beijing

19. RICH with Multiple Radiators
NIM A548(2005)383
Demonstration of principle
4×4 array of H8500 (85% effective area)
Conventional
4cm thick aerogel
n=1.047
sc=22.1mrad Npe=10.7
Multiple Radiators
sc=14.4mrad Npe=9.6
2 layers of 2cm thick
n1=1.047, n2=1.057
p/K separation with focusing configuration ~

20. Toru Iijima, BBCB2007 @ IHEP, Beijing
Multialkari
photocathode
Pixel APD
144ch HAPD
-10kV
15~25mm e-
Newly developed under collaboration with Hamamatsu Photonics.
4 APD chips (6x6pixel/chip)
5x5mm2 pixel
64% effective area
High gain: O(104)
2007/11/27
Toru Iijima, IHEP, Beijing

21. Other possibilities Geiger-mode APD MCP-PMT High gain(~106)
Good time resolution(~50ps/p.e.)
Stable operation.
Need
Smaller pore size (25m  <10m)
Better collection eff.
Lifetime ?
Geiger-mode APD
High gain(~106)
High Q.E.(>50%)
B-field immunity independent of the direction.
Concerns
High noise rate (~200KHz/mm)
Size (~1x1mm2 3x3mm2)
Radiation damage ?
Light collector
□3~5mm (IN)
□1-2mm(OUT)
G-APD
□1~3mm
Cherenkov Photons
17deg max. for n=1.05
BURLE

22. RICH w/ TOF Capability
Possible PID improvement in low momentum region.
Two timings can be used;
“Ring hit” : Cherenkov photons from aerogel.
sphoton ~ 60ps strack ~ 60ps/sqrt(9) =20ps
“Window hit”: Cherenkov photons from glass window of PMT
strack ~10ps possible (from the TOF Nagoya).
Aerogel
PMT IP
DTOF1(K-p)
D ~ 0.2m
DTOP
L ~ 1.8m
Ring Hit
DTOF1 + DTOP
Window Hit
DTOF2 w/ L+D

23. Beam Test w/ BURLE MCP-PMT
December KEK-PS T2
Beam Test w/ BURLE MCP-PMT
Multi-anode MCP-PMT
BURLE
13 channels readout by
FTA820 amplifier (ORTEC)
L-edge discri (Phillips)
KC3781A TDC (Kaizu works)
Start counter: HPK R3809U MCP-PMT 1cm quartz radiator Start time resolution = 10ps
Cherenkov photon
from aerogel
from window
MWPC
Aerogel
radiator
1.045
1.053
Time resolution for “window hits”
(Time walk corrected)
TOF test w/ beam p and p (2GeV/c) p
s = 34.3±1.1ps
= 36.2±1.3ps p
TDC count(/25psec)

24. Summary
RICH detectors, based on Quartz and Aerogel, are being developed for the Super-KEKB/Belle
Key technologies;
Radiators: Accurately polished quartz
Highly transparent aerogel
Photodetectors: MCP-PMT / HAPD / Geiger-mode APD
Ideas to overcome performance limitations
TOP counter: chromatic dispersion  GaAsP, focusing-TOP
Aerogel RICH: emission point uncertainty  multiple-radiator
Prototype detectors with the newly developed potodetectors will be tested in beams by summer 2008.
 Finalization of detector design.
Stay Tuned.
2007/11/27

25. Ad:BNM2008 Workshop (Jan.24-26,2008)
2007/11/27
Toru Iijima, IHEP, Beijing

26. Toru Iijima, BBCB2007 @ IHEP, Beijing
Backup slides
2007/11/27
Toru Iijima, IHEP, Beijing

27. Toru Iijima, BBCB2007 @ IHEP, Beijing
Particle ID in Belle
Calibratiopn by
D*+D0p+, D0K-p+
eff.(KK) >90%
fake(pK)<10%
2007/11/27
Toru Iijima, IHEP, Beijing

28. Motivation of PID Upgrade
To cope with increasing background (x20).
TOF may not survive
ACC seems to be OK
Improve separation for K/p, and also for m/p hopefully.
Extend momentum coverage in the forward endcap.
Endcap-ACC (n=1.03) functions
only for flavor tagging
Reduced material thickness, and
more homogeneous distribution.
30% in total = 18% (ACC) + 12% (TOF)
PMTs dominate for ACC
Physics Targets
B  pp/Kp, Dp/DK
B rg/K*g (bdg/sg)
B  K ll, K n n
Full reconstruction
Less systematics for precise
measurements
2007/11/27
Toru Iijima, IHEP, Beijing

29. Chromaticity
Detection time depending on the wavelength of Cherenkov photons
Worse time resolution
 Worse ring-image separation
 Propagation velocity depending on l in the quartz bar

30. Toru Iijima, BBCB2007 @ IHEP, Beijing
Focusing TOP (2)
Dqc~1.2mrad over sensible l range
 Dy~20mm (~quartz thickness)
We can measure l dependence and obtain good separation even with narrow mirror and readout plane, because of long propagation length.
Not need focusing block
Dqc~1.2mrad
Virtual readout screen
22mm x 5mm matrix
Focusing mirror
1850mm
2007/11/27
Toru Iijima, IHEP, Beijing

31. Single Photon Angle Resolution
Main contributions come from
Detector granularity
Emission point uncertainty
All other contributions (not fully understood yet)
Emission point uncertainty d > 2cm
2007/11/27
Toru Iijima, IHEP, Beijing

32. Beam Test Results of Multi-Radiator Aerogel-RICH

33. Defocusing Config. More affected by background.
n1 n2 n1>n2
More affected by background.
Photons from higher n layer are dumped.
Overlap of K-ring from n1 and p-ring from n2.

34. Toru Iijima, BBCB2007 @ IHEP, Beijing
PID Capability
Based on a likelihood approach.
Simulation w/ the level of bkg. expected at Super-Belle.
Focusing radiator improves PID for p>3GeV/c
dE/dx
(CDC)
Kaon Cherenkov Threshold
2007/11/27
Toru Iijima, IHEP, Beijing

35. TOF w/ MCP-PMT High-resolution TOF using Cherenkov light
Y.Enari NIM A547 (2005) 490
K.Inami A560 (2006) 303
TOF w/ MCP-PMT
High-resolution TOF using Cherenkov light
Small-size quartz :
Cherenkov light (Decay time ~ 0)
MCP-PMT :
TTS < 50ps for single photon
Results 1
4cm quartz radiator
s(elec.) = 8.8psec
Results 2 w/ improved s(elec)
1cm quartz radiator
s(elec.) = 4.7psec
s(TOF) = 10.6ps
s(TOF) = 6.2ps
Time correlated single photon
counting module
SPC-134 (Becker&Hickl GMbH’s)

36. TOF in Aerogel-RICH Worth for studying ! 1.5GeV/c 2GeV/c 4GeV/c
Ring Hit --
147ps
37ps
Window Hit
323ps
184ps
47ps
Worth for studying !

37. Time resolution for Ring Hits
Obtained time resolution for Cherenkov photons from aerogel agrees well with the value from the bench tests.
Resolution for the full ring (Npe~10) would be about 20ps.
TDCBURLE-TDCSTART COUNTER
Distribution of the hits on MCP-PMT (13 channels were readout).
Corrected distribution using the track information.
= 51.4±1.1ps