# Presentation: 273312

## Particle Identification at Belle     ~ Present status and upgrade plan ~ Takahiro Matsumoto / Tokyo Metropolitan University

- Belle/KEKB plan
- Belle PID upgrade plan
- TOP counter
- Aerogel RICH counter
- Summary

- Takahiro Matsumoto

- 2005/01/11

## Introduction

*Introduction*

- Goal of B-factory project
- Explore variety of B decays
-  Establish CKM scheme of CP violation
- Discovery of New physics (if possible)
- Brief history
- 1999 : KEKB/Belle operation started
- 2001 : Establish CP violation in B decay
- 2003 : Hint of new physics in BKS?
- 2004 : Direct CP violation in BK

- Upgrade of detector is planned to continue exciting B physics race (Super-B project).                     Particle ID section is one of the most active area at Belle.

- Takahiro Matsumoto

- 2005/01/11

## International Collaboration: Belle

***International Collaboration: Belle***

**IHEP, Vienna**
**ITEP**
**Kanagawa U.**
**KEK**
**Korea U.**
**Krakow Inst. of Nucl. Phys.**
**Kyoto U. **
**Kyungpook Nat’l U. **
**EPF Lausanne **
**Jozef Stefan Inst. / U. of Ljubljana / U. of Maribor**
**U. of Melbourne**

**Aomori U.**
**BINP**
**Chiba U.**
**Chonnam Nat’l U.**
**U. of Cincinnati**
**Ewha Womans U.**
**Frankfurt U.**
**Gyeongsang Nat’l U.**
**U. of Hawaii**
**Hiroshima Tech.**
**IHEP, Beijing**
**IHEP, Moscow **

**Nagoya U.**
**Nara Women’s U.**
**National Central U.**
**Nat’l Kaoshiung Normal U.**
**National Taiwan U.**
**National United U.**
**Nihon Dental College**
**Niigata U.**
**Osaka U.**
**Osaka City U.**
**Panjab U.**
**Peking U.**
**U. of Pittsburgh**
**Princeton U.**
**Riken**
**Saga U.**
**USTC**

**Seoul National U.**
**Shinshu U.**
**Sungkyunkwan U.**
**U. of Sydney**
**Tata Institute**
**Toho U.**
**Tohoku U.**
**Tohuku Gakuin U.**
**U. of Tokyo**
**Tokyo Inst. of Tech.**
**Tokyo Metropolitan U.**
**Tokyo U. of Agri. and Tech.**
**Toyama Nat’l College**
**U. of Tsukuba**
**Utkal U.**
**VPI**
**Yonsei U.**

- Takahiro Matsumoto

- 2005/01/11

## Belle PID Group (for Upgrade)

- Tokyo Metropolitan U.  ( Aerogel RICH, electronics )
- T.Sumiyoshi, T.Matsumoto, T.Seki, S.Yamamoto, T.Nakagawa
- KEK ( TOP, Aerogel RICH )
- I. Adachi, S.Nishida, H.Ikeda, Y.Uchida
- Ljubliana Institute ( TOP, Aerogel RICH )
- P.Krizan, S.Korpar, M.Staric, A.Gorisek, R.Pestonik, S.Fratina
- Nagoya U. ( TOP, Aerogel RICH )
- T. Ohshima, T.Iijima, K.Inami, Y.Kozakai, T.Kubota, H.Nakano, K.Aoki, Y.Mazuka
- Chiba U. ( Aerogel RICH,  aerogel production)
- H.Kawai, Y.Unno, M.Konishi, T.Fukushima, M.Tabata
- Toho U. ( Aerogel RICH )
- S.Ogawa, S.Ohtake, M.Iwabuchi

- Takahiro Matsumoto

- 2005/01/11

## KEKB Collider

**8 GeV e****-**** x 3.5 GeV e****+**

** ****@ 1.2A x 1.6A**

**L****peak**** = 1.39 x 10****34 ****sec****-1****cm****-2 **

- 11mrad crossing

**~300 fb****-1**** on Y(4S)  (330 M BB)**
** ****~30 fb****-1**** below Y(4S)**

- Takahiro Matsumoto

- 2005/01/11

## Continuous Injection

- [CERN courier Jan/Feb 2004]

- No need to stop run
- Always at ~max. currents, luminosity

**~30% more ****** ***L dt***

- both KEKB & PEP-II

**HER current**

**LER current**

**continuous injection (new)**

- normal injection (old)

***Luminosity***

- 0

- 12

- 24

- Time

**~1 fb****-1****/day !**
** ****(~1x10****6 ****BB)**

**-**

- Takahiro Matsumoto

- 2005/01/11

## Slide 7

- Takahiro Matsumoto

- 2005/01/11

## Belle detector

******/ *****K******L***** detection**
-  14/15 lyr. RPC+Fe

**CsI(Tl)**
-    16*X**0*

**Si vtx. det.**
-    3(4) lyr. DSSD

**TOF conter**

**SC solenoid**
-    1.5T

**8 ****GeV**** *****e*******

**3.5 ****GeV**** *****e*******

-  **Aerogel Cherenkov cnt.**
-               n=1.015~1.030

**C****entral**** D****rift**** C****hamber**
-        small cell +He/C2H5

- Takahiro Matsumoto

- 2005/01/11

## Particle ID at Belle

*Particle ID at Belle*

- eff.(KK) ~90%

- fake(K)~10%

- Takahiro Matsumoto

- 2005/01/11

## Successful of PID (example)

- +- : 231.4
- K   :   83.3
- qq    : 168.3
- total : 483

- B0  +(140/fb)

- A	= 0.58 0.15(stat) 0.07(syst)
- S  	= 1.00 0.21(stat) 0.07(syst)

- BaBar

- Belle

- [to appear in PRL, hep-ex/0401029]

- Takahiro Matsumoto

- 2005/01/11

## Super-B factory ( 2008~ ? )

*Super-B factory ( 2008~ ? )*

- Aiming  **L = 2.5-5 x 10****35**** cm****-2****s****-2**
- 1st goal:** ∫*****L dt***** = 5 ab****-1****                   **(long term:** 50 ab****-1**** )**

- 8GeV e+
- 4.1 A

- 3.5GeV e
- 9.6 A

- Super-KEKB

- Super B Factory at KEK

- Takahiro Matsumoto

- 2005/01/11

## B physics Roadmap

- Discovery of CPV
-     in *B* decays

- Precise test of SM
- and search for NP

- Study of NP effect
-  in *B* and  decays

- Identification of SUSY
-  breaking mechanism

- time or
- integrated luminosity

- Yes!!

- sin21, CPV in *B*,
- 3, *V**ub*, *V**cb*, *b**s*,
*b**s**ll*, new states etc.

- Anomalous
- CPV in *b**sss*

- NP discovered
- at LHC (2010?)

- Now
- 300 fb-1

- if NP=SUSY

- Tevatron (m~100GeV)  LHC (m~1TeV)
- KEKB (1034)	          SuperKEKB (1035)
- 	Concurrent program

- Takahiro Matsumoto

- 2005/01/11

## Belle Detector Upgrade

- / *K**L* detection
- Scintillator strip/tile

- CsI(Tl) 16*X**0*

- Si vtx. det.

- SC solenoid
- 1.5T   lower?

*Belle Detector Upgrade*

- 2 pixel lyrs. + 3 lyr. DSSD

- pure CsI (endcap)

- PID
- “TOP” + RICH

- Tracking + *dE/dx*
-   small cell + longer arm

- Takahiro Matsumoto

- 2005/01/11

## Requirements for Particle ID

*Requirements for Particle ID*

- Further Improvement on K/ separation
- Currently, Slightly worse performance than BaBar
- Missing high momentum PID in the forward endcap
- Present endcap-ACC is used only for flavor tagging
- High momentum K/ sep.   Low momentum / sep.
- Also useful for study of AFB in BK(*) 

- Operational under very high bkg. ( x 20 )
- TOF may not survive
- ACC seems to be OK
- Reduction of radiation length
- 30% in total = 18% (ACC) + 12% (TOF)
- PMTs dominate for ACC

- Belle

- BaBar

- * under 10A total current

- Takahiro Matsumoto

- 2005/01/11

## PID upgrade 

*PID upgrade *

- Baseline
- Barrel  TOP Counter
- Endcap  Aerogel RICH

- Other option
- Focusing DIRC
- TOF w/ finer segmentation ( with Barrel-ACC )

- Takahiro Matsumoto

- 2005/01/11

## TOP Counter Concept

*TOP Counter Concept*

- Quartz-based RICH counter
- detect internally reflected Cherenkov light (like DIRC at BaBar)
- Reconstruct the image in (X,TOP) instead of (X,Y).
- 		“TOP” = Time Of Propagation
- Possible if TOP < 100ps for each arriving photon.

- NIM A453(2000)331

- TOF from IP to quartz bar is also used.

- C     : Cherenkov angle             : horizontal emission angle  L      : distance for light travel vg() : group velocity of light

- Takahiro Matsumoto

- 2005/01/11

## Proximity focusing in X measurement
Simplified structure and easier installation.
Loose requirement for X (~5mm)

Well polished quartz radiator

Photodetection by linear-anode PMT

Flipped images can be resolved by widening the bar width (>20cm). 

- Simplified structure and easier installation.
- Loose requirement for X (~5mm)
- Well polished quartz radiator
- Photodetection by linear-anode PMT
- Flipped images can be resolved by widening the bar width (>20cm).

*“**Bar TOP” Counter*

- Simulation
- 2GeV/c, =90 deg.

- -ray,
- had. int.

- K
- 

- Takahiro Matsumoto

- 2005/01/11

## TOP Counter Design

*TOP Counter Design*

- Quartz radiator: 40cm x 2cm x 255cm
- 	 18 segmentation in r-
- Photodetection: MCP-PMT
-     w/ linear anode  (5mm)
- Good time resolution: < 40ps/photon
- Single photon sensitive up to 1.5T
- Number of PMTs (channels)
- 15 pcs. (60ch) /module
- 270 pcs. (1080ch) / total
- 	for 1 read-out plane (LoI design)
- 810 pcs. (3240cn) / total
- 	for 3 read-out planes (present baseline)

- 16% x X0

- R=115~125cm
- Z=-72.5~182.5cm

- Takahiro Matsumoto

- 2005/01/11

## Beam Test w/ Prototype

*Beam Test w/ Prototype*

- Demonstration of principle w/
- 1m(L)x20cm(W)x2cm(T)
- R5900-00-L16

- @ KEK PS 2 line
-      3 GeV/c  beam
- in=in=90 degree

*Test counter*

-  Clear ring image
-  Reasonable
- 	time resolution
-  Enough bar quality

- Takahiro Matsumoto

- 2005/01/11

## Quartz Radiator

- time) measured w/ beam
- (“Butterfly TOP” w/ R5900-L16)

- Bar#1

- Bar#2

*Quartz Radiator*

- Synthetic fused silica
- Long transmission
- Good polishability
- Radiation hardness
- Shin-etsu, “SUPRASIL-P30”
- T~90% at  = 250nm
- Polishing accuracy at Okamoto Kogaku Co. (Yokohama)

- Takahiro Matsumoto

- 2005/01/11

## MCP-PMT (SL10)

- 1x4 linear-anode MCP-PMT newly developed for TOP readout.

| #MCP stage | 2 |
| --- | --- |
| Gain (HV) | 2x106 (-3.5KV) |
| MCP hole dia. | 10m |
| Geometrical collection eff. | 50% |
| #pixel /size | 1x4 / 5mmx22mm |
| Effective area/
Total area | 64% |

- Under Development

- Takahiro Matsumoto

- 2005/01/11

## R&D for Readout ASIC

- Time-to-Analog Converter  Time resolution <~20ps.
- Double overlap gates  Less dead time (~100ns).
- 0.35 CMOS process.
- 2nd batch TAC-IC was submitted to VDEC (U. Tokyo)

- 40MHz CLOCK

- “TAC-IC” Concept

- Takahiro Matsumoto

- 2005/01/11

## Performance of TOP

- Separation power

- Npe

- Single photon resolution

- Light propagation velocity

- Takahiro Matsumoto

- 2005/01/11

## Efficiency/fake (LoI)

-  Large drop around =70~80 degree, due to chromaticity.
-  Need to optimize TOP design (Bar length, width, ch. division, etc.)

- Takahiro Matsumoto

- 2005/01/11

## Segmented TOP

- Decreased (TOP) ,         but avoid chromatic effect
- 3 times more readout
- No need for gluing
- much easier construction
- Various version is tested.
- For example,

- Belle : (K) ~ 90%, fake() ~ 10%
- TOP : (K) ~ 98%, fake() ~2 %

- K/ separation @ 3 GeV/c

- Takahiro Matsumoto

- 2005/01/11

## Robustness against Beam BG

- Efficiency and fake rate for KID
- Bialkali photo-cathode option
- Estimated background rate
- Based on a simulation w/ spent
- 	electron generator
- Dominated by e+e conversion
-  hit rate = 44kHz/counter at L=1034
- 	6.8 photons/hit/counter
- ~900kHz-hit/counter at BG x 20
- ~80kHz/ch
- Stable performance even for 10 times more BG rate of our estimate

- Our estimate

- (/counter)

- Takahiro Matsumoto

- 2005/01/11

##  Aerogel RICH

- Proximity focusing RICH with an aerogel radiator
- Proximity focusing  Due to limited space
- Target : K/ sep. > 4  @ 0.7 ~ 4 GeV/c
- c()– c(K) ~ 23mrad (n=1.05)
- separation ifC(meas.)  ~14 mrad with Npe=6
- Key components
- High optical quality aerogel
-   with n = 1.05
- Photon detector
- Single photon
- Position sensitive
- Strong B field (1.5T)
-  HPD/HAPD
- Readout electronics
- Mechanical structure

- Takahiro Matsumoto

- 2005/01/11

## Aerogel radiator

- Used as Threshold counter at Belle
- K/ separtion with ON/OFF signal
-  Aerogel radiator, n = 1.01 ~ 1.03
- adequate for a few GeV range
- Hydrophobic aerogel by surface modification
- optical quality is improved
- But not devlopped for n=1.05 !
- Because both /K emits cherenkov photon...

- Takahiro Matsumoto

- 2005/01/11

## Aerogel production improvement

- R&D in cooperation with Matsushita
- Goal
- better optical quality for n~1.05 hydrophobic aeogel
- Method
- A new solvent(Di-Methyl-Formamide instead of Methyl-alcohol)
- Precursor(Mthyl-silicate-51) from a different supplyer
-  Considerable improvement

- Takahiro Matsumoto

- 2005/01/11

## Beam test with Flat-panel PMT

*Beam test with Flat-panel PMT*

- Demonstration of principle
- Various aerogel samples
- 4×4 array of H8500
- 85% effective area
- Analog memory readout
- 64 ch x 16 =1024 ch ADC  pipeline

- Takahiro Matsumoto

- 2005/01/11

## Results

- Chrenkov angle/#photon
- 0 ~ 14 mrad
- (em.) ~ 8.6 mrad
- (pix.) ~ 6.4 mrad
- * Trying to understand Rest component ~ 7 mrad,  (chromatic dispersion, aerogel uniformity, surface effects etc.).
- Npe ~6
- Naïve estimation of  / track
- 0/sqrt(Npe) ~ 5.7 mrad
- K/ separation @ 4 GeV
- ~ 4 is expected
- Demonstrated by Data!

- Takahiro Matsumoto

- 2005/01/11

## Photo detector

*Photo detector*

| Package | 72x72mm2 |  |
| --- | --- | --- |
| # of pixels | 12x12(6x6/chip) |  |
| Pixel size | 5x5mm2 |  |
| Effective area | 64% |  |
|  | PD | APD |
| Gain | 2000 | 20000 |
| Cd | 10pF | 80pF |
| I(leak) | 10nA | 30nA |

- Requirement on Photodetector
- Sensitive to Single photon
- Position sensitive
- Immune to Magnetic Field (1.5T)
- HPD and HAPD option is studied.
- Developed between HPK and Belle

- Takahiro Matsumoto

- 2005/01/11

## Performance of HAPD

- Very recently, we could start to test             12 x 12 HAPD
- Due to problem of out-gas etc.
- Modification on ceramic case was done
- However, 2 dead  out of 4 chips...
- Single photon can be observed.              Further studies (Uniformity, crosstalk,  incident angle dependence etc.) are underway.

- Delivered sample
- QE 11.3% at 420nm
- Max high voltage -8KV
- Max bias voltage 335V

- Single Photoelectron

- Muliti Photoelectron

- Takahiro Matsumoto

- 2005/01/11

**Notes:**
Multi Photoelectron

## Aerogel RICH readout
Total ~ 100k channel!
Readout scheme  pipeline
Only record hit information
Basic parameters for the ASIC 
CMOS-FET
Gain=10V/pc
Shaping time=0.15sec
VGA=1.25~20
18 channels/chip
Power consumption : 5 m W/channel
3rd batch was submitted to VDEC (More protection to noise was done )

- Total ~ 100k channel!
- Readout scheme  pipeline
- Only record hit information
- Basic parameters for the ASIC
- CMOS-FET
- Gain=10V/pc
- Shaping time=0.15sec
- VGA=1.25~20
- 18 channels/chip
- Power consumption : 5 m W/channel
- 3rd batch was submitted to VDEC (More protection to noise was done )

*Readout Electronics*

- □4.93[mm]

- Shaper

- Takahiro Matsumoto

- 2005/01/11

##  Mechanical design

-  Aerogel radiator
- Hexegonal tiling to minimize aerogel boundary
- side length, 125 mm
- Photo detector
- Total PD : 564, 6 sectors
- Cover 89.0% of area

- Aerogel

- Photo detector

- Takahiro Matsumoto

- 2005/01/11

## Aerogel RICH, performance

- Based on Simulation study, likelihood approach
- K/ efficiency by keeping fake rate = 5%
-  > ~ 95% up to 4 GeV/c

- Takahiro Matsumoto

- 2005/01/11

## Dual-(Multi-) radiator Scheme

- Focusing & defocusing schemes
- Solve a dilemma: thicker radiator for more Npe deteriorates an angle resolution
- Advantage from manageable refractive index

- 1.046

- 1.051

- 1.056

- 1.061

- 1.051

- 1.034

- 1.029

- 1.056

- Focusing type

- Defocusing type

- n1

- n2

- n1<n2

- n1>n2

- n1

- n2

- Takahiro Matsumoto

- 2005/01/11

## Beam test results(1)

- single photon resolution

- # of Npe

- A

- B

- C

- A

- B

- C

- A

- B

- C

- 1.056

- 40mm

- 1.046

- D

- D

- D

- conventional
- dual
- multiple

- ●

- ▲

- ■

- Improved !!

- Increased !!

- Takahiro Matsumoto

- 2005/01/11

## Beam test results(2)

- Separation power at 4GeV/c = 4.2 for K/

- A

- B

- C

- 5.2 mrad

- D

- Optimal values

|  | resolution | thickness |
| --- | --- | --- |
| conventional | 6.7 mrad | 20mm |
| dual | 6.2 mrad | 40mm |
| multiple | 5.2 mrad | 30mm |

- Comparison of angle resolution per track

- optimal

- Takahiro Matsumoto

- 2005/01/11

## Summary

- We are developing new types of RICH detector for the upgrade of the Belle detector.
- Barrel TOP counter
- 	Internally reflected Cherenkov light with (X,T) readout.
- Endcap  Aerogel RICH
- 	Proximity focusing with  aerogel radiator(s).
- Target performance: >4 K/ separation up to 4 GeV/c
- Target date : ~ 2008?
- Photo-detection is most key issue for the development.
- MCP-PMT for TOP
- Also trying to test GaAsP photocathode for the improvement.
- H(A)PD for Aerogel-RICH

- Takahiro Matsumoto

- 2005/01/11

## Backup slides

- Takahiro Matsumoto

- 2005/01/11

## dE/dx

- He : C2H6 = 50 : 50
- Low Z gas to avoid multiple scattering
- Keeping good dE/dx resolution
- With higher composition of hydro-carbons
- dE/dx resolution ~ 6%
- 80% truncated mean
- * 50 layers in total

- Takahiro Matsumoto

- 2005/01/11

## Time Of Flight Counter

- Measure  ( = L/t ), and obtain m with p from tracking
- t ~ 100ps with
- Fast scintillator, BC408
- Long att. Length ~ 4m
- Larger photon coverage with FM-PMT (R6680) (under 1.5T)

- _PID for P< 1.2 GeV/c_

- Takahiro Matsumoto

- 2005/01/11

## Aerogel Cherenkov Counter (1)

- Threshold counter
- K/ separtion with ON/OFF signal
-  Aerogel radiator, n = 1.01 ~ 1.03
- adequate for a few GeV range
- Hydrophobic aerogel by surface modification
- optical quality is improved

- Takahiro Matsumoto

- 2005/01/11

## Aerogel Cherenkov Counter (2)

**ACC :**** **
**K/******** in 1.5<p<3.5 GeV/c**
**Barrel : 960 modules **
**in 60 ********-segments**
**n = 1.010 ~ 1.028**
**FWD endcap : 228 modules **
**in 5 layers**
**n = 1.030**

- Npe = 10~ 20

- Takahiro Matsumoto

- 2005/01/11

## Combined performance

- Typical performance
- Eff (KK)   ~ 88%
- Fake (K) 8~10%
- up to 4 GeV/c

- Efficiency/fake rate for Barrel, prob > 0.6

- Takahiro Matsumoto

- 2005/01/11

## Segment TOP Performance

- Target: >4 K/ @ 4GeV/c over =35-135deg.

- ~2.5   @ 0.6GeV/c

**TOP performance (base design)**

**DIRC performance (from RICH2002)**** **

- Want improvement
- to achieve the target !

- Takahiro Matsumoto

- 2005/01/11