Study of a Proximity Focusing RICH with Aerogel Radiator for Future Belle Upgrade
Toru IijimaNagoya University
October 18, 2007
6th International Workshop on Ring Imaging Cherenkov Counters (RICH2007) in Trieste
12007/10/18 Toru Iijima, RICH2007 @ Trieste
Belle PID upgradeRadiator design/optimizationPhotodetector candidateTOF capabilitySummary
Collaboration
I.Adachi a, R. Dolenc b, A. Petelin b, K. Fujita c, A. Gorisek b, K. Hara c, D. Hayashi c, T. Iijima c, K. Ikado c, H. Kawai d, S. Korpar b,e, Y. Kozakai c, P. Krizan b,f, A. Kuratani d, Y. Mazuka c, Y. Miyazawa g,
S. Nishida a, I. Nishizawa h, S. Ogawa i, R. Pestotnik b, T. Sumiyoshi h, M. Tabata d, M.Yamaoka c
a) High Energy Accelerator Research Organization (KEK), Japanb) Jozef Stefan Institute, Slovenia
c) Nagoya University, Japand) Chiba University, Japan
e) University of Maribor, Sloveniaf) University of Ljublijana, Slovenia
g) Tokyo University of Science, Japanh) Tokyo Metropolitan University
i) Toho University, Japan
Belle upgrade (Super-Belle) To cope with increased background (present x
~20) To improve the performance (ex. PID).
SC solenoid1.5T
New readout and computing systems
CsI(Tl) 16X0
pure CsI (endcap) Aerogel Cherenkov counter + TOF counter “TOP” + RICH
Si vtx. det. 4 lyr. DSSD 2 pixel/striplet lyrs. + 4 lyr. DSSD
Tracking + dE/dx small cell + He/C2H5remove inner lyrs.
/ KL detection 14/15 lyr. RPC+Fe tile scintillator
Toru Iijima, RICH2007 @ Trieste 42007/10/18
Motivation of PID Upgrade To cope with increasing background.
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, andmore homogeneous distribution. 30% in total = 18% (ACC) + 12% (TOF) PMTs dominate for ACC
Physics TargetsB /KD/DKB /K*(bd/s)B K ll, K Full reconstruction
Less systematics for precise
measurements
Belle PID Upgrade Option Barrel TOP (Time-Of-Propagation)
Counter Endcap Proximity Focusing Aerogel-
RICHBarrel PID TOP
Talk by K.Inami
Endcap-PID Aerogel-RICH
Proximity Focusing Aerogel RICH
Aerogel radiator (n~1.05, ~2cm) + photodetector (x ~ 5mm)
Proximity focusing geometry No mirror complex. Suitable for collider and space
experiments.
>4 K/ for 0.7 < p < 4.5 GeV/c@ 4GeV/c, ()=310mrad.
()-(K)=23mrad.
Distance between aerogel to photodetector = 200mm.
Track Incident angles = 17-34deg.
Beam Test w/ Flat Panel PMT 4×4 array of H8500 52.5mm pitch 84% effecive area. 1024 channel Two MWPC for tracking
NIM A521(2004) 367
Typical Results
0 = 14.8 mrad. <Npe> = 6.2
Want more photons !14.8
5.96.2
track
mradmrad 4 K/
@ 4GeV/c
Single Photon Angle ResolutionMain contributions come
from Detector granularity
Emission point uncertainty
All other contributions (not fully understood yet)
8a mrad
4[d mrad/ cm] d[cm]
6r mrad
ad
Emission point uncertainty dominates @ d > 2cmEmission point uncertainty dominates @ d > 2cm
RICH with Multiple RadiatorsNIM A548(2005)383
Conventional4cm thick aerogeln=1.047
c=22.1mradNpe=10.7
Multiple Radiators
c=14.4mradNpe=9.6
2 layers of 2cm thick n1=1.047, n2=1.057
/K separation with focusing configuration ~ 4.8 @4GeV/c
Demonstration of principle 4×4 array of H8500 (85% effective area)
Defocusing Config.
More affected by background. Photons from higher n layer are
dumped. Overlap of K-ring from n1 and -
ring from n2.
“Defocusing”
n1 n2 n1>n2
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
Poster by R. Pestotnik et al.
dE/dx (CDC) Kaon Cherenkov Threshold
Want more robustness in low p < 1.5 GeV/c
Focusing
Defocusing Single layer
Photodetector Candidates HAPD: Hybrid Avalanche Photodiode S. Nishida MCP-PMT: Micro-channel-plate PMT P. Krizan Giger-mode APD S. Korpar
PMT MCP-PMT HPD / HAPD G-APD
Gain >106 ~ 106 ~ 103
X10 ~ 100 w/ APD
~ 106
Quantum Eff. ~ 20%, ~ 400nm (bialkali) ~ 80%, ~600nmto be checked
Collection Eff. 70% 60% 100% 50%
Time resolution
~ 300ps ~ 30ps ~ 150psDepends on readout
<100psTo be checked
B-field immunity
× △ Depends on angle ○
Problems lifetime Noise, size
See talks by
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 14cm quartz radiatorelec.) = 8.8psec
Results 2 w/ improved (elec)1cm quartz radiatorelec.) = 4.7psec
(TOF) = 10.6ps
Y.Enari NIM A547 (2005) 490K.Inami A560 (2006) 303
Time correlated single photon counting moduleSPC-134 (Becker&Hickl GMbH’s)
(TOF) = 6.2ps
RICH w/ TOF Capability Possible PID improvement in low momentum region. Two timings can be used;
“Ring hit” : Cherenkov photons from aerogel.
photon ~ 60ps track ~ 60ps/sqrt(9) =20ps
“Window hit”: Cherenkov photons from glass window of PMT
track ~10ps possible (from the TOF R&D @ Nagoya).
AerogelPMT
IP
TOF1(K-)
D ~ 0.2m
TOP
L ~ 1.8m
Ring HitTOF1 + TOP
Window HitTOF2 w/ L+D
TOF in Aerogel-RICHL = 1.8m, D=0.2m, Normal incidence
- 0.05000
0.00000
0.05000
0.10000
0.15000
0.20000
1.0 2.0 3.0 4.0 5.0
Momentum (GeV/ c)
DTIM
E/D
TO
F(ns
)
DTOF1(K- pi)DTOP(K- pi)DTIME(K- pi)DTOF2(K- pi)
TOF2(K- ) with "Particle Hit"
TIME(K- ) with "Ring Hit" = TOF1+TOP
TOF1(K- )
TOP(K- )
Worth for studying !
1.5GeV/c
2GeV/c 4GeV/c
Ring Hit -- 147ps 37ps
Window Hit
323ps 184ps 47ps
Beam Test Setup BURLE 85011-501 to measure
the ring and window photons. 13 channels are 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 (pre
calibrated using two identical sets.)
December 2005 @ KEK-PS T2
Burle MCP-PMT (85011-501) 8x8 multi-anode.
Pitch = 6.45mm / gap=0.5mm
Bialkali photocathode 2MCP steps Gain ~ 0.6x106
25m pores
Bench test w/ pulse laser(HPK PLP-02)
Single photon irradiation <Npe> dependence
Time Resolution for Window Hits Optimization of discriminator threshold and HV. Time walk correction applied.
Threshold scan @ HV=2.4kV
Tim
e re
solu
tio
n(p
sec)
Threshold(mV)1 photon
Eve
nt
TDC count(/25psec)
TDCBURLE-TDCSTART COUNTER
(Time walk corrected)
1- pixel result
Operation point = 34.3±1.1ps
Time Resolution for Window Hits (cont’d) Signals are observed also in the neighboring channels. Time resolution can be improved by combing hits.
Hit distribution<ADC> for each ch.
Result using average over 5 pixels
55
1I
ITDC
= 28.1±1.5ps
pixel hit by beam
Possible sources Photon reflections
1. in window2. betw. PC and
MCP Electrons ‘
3. reflection at MCP
4. spread @ MCP-> anode.
5. spread @ PC->MCP
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
TOF Tests w/ pions and protons TOF tests using 2, 2.4, 3.4 GeV/c beam of pions + protons. Distance (start counter - MCP-PMT) = 65cm
p
TOFp-
TDCBURLE-TDCSTART COUNTER @ 2 GeV/c
= 36.2±1.3ps
1- pixel result
TOF Tests w/ pions and protons TOF tests using 2, 2.4, 3.4 GeV/c beam of pions + protons. Distance (start counter - MCP-PMT) = 65cm
p
TOFp-
TDCBURLE-TDCSTART COUNTER @ 2 GeV/c
= 36.2±1.3ps (1-pixel)
5- pixel result
TOFp-
= 33.4±2.2ps (5-pixel)
Remarks TOF supplement the RICH
Very good /K separation in the low mom. region, also good K/p. positive ID of kaons, below the K threshold. Redundant and robust PID system against background.
In case of the MCP-PMT option, TOF should be used, taking full advantage of the sensor resolution. It helpd to recover the performance loss due to ~60% collection
efficiency.
It is also interesting to see the resolution with HAPD or G-APD options.
For the “Window hit”, we need precise time recording only for each sensor unit, not for each pixel (high threshold for analog sum).
Summary We are developing a proximity focusing RICH with aerogel
radiator to upgrade the forward endcap PID of the Belle detector.
The idea of using multiple aerogel layers with varying refractive index enables us to increase Npe without deteriorating the angle resolution. K/ separation close to 5 @ 4 GeV/c Design optimization based on the focusing config. being
finalized.
The detector can be used also as a TOF counter. Beam tests w/ BURLE 85011-501 MCP-PMT demonstrate TOF
~30ps for “window hits”. Extend PID capability into the low momentum region. More robust PID system can be constructed.
Gear up to the construction! The major remaining issue is the photosensor.
Stay tuned !Stay tuned !
Backup slides
Toru Iijima, RICH2007 @ Trieste 262007/10/18
Particle ID in Belle
fake(K)<10%
eff.(KK) >90%
Calibratiopn byD*+D0+, D0K-+
Toru Iijima, RICH2007 @ Trieste 272007/10/18
Beam Test Results ofMulti-Radiator Aerogel-RICH