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