Belle SVD status & upgrade plans

O. Tajima (KEK)

Belle SVD group

KEKB KEKB : the highest luminosity in the world: the highest luminosity in the world

3.5 GeV e+ 8.0 GeV e

ee (4S)

with = 0.425

22 mrad crossing angle

Located in Tsukuba, Japan

Lpeak = (1.651034)/cm2/sec ~ 1M BB pairs/day

integrated luminosity = 0.63 /ab

_

Belle detector

Belle DetectorBelle Detector

KL detector14/15 layer RPC+Fe

Electromagnetic CalorimeterCsI(Tl) 16X0

Aerogel Cherenkov Counter n = 1.015~1.030

TOF counter

3.5 GeV e+

Central Drift Chamber momentum, dE/dx 50-layers + He/C2H6

charged particle tracking

K/ separation

K/ separation

Si Vertex Detector( SVD )

4-layer DSSD

B vertex Muon / KL identification

, 0 reconstructione+-, KL identification

8.0 GeV e-

SVD GroupFrankfurt U., U. Hawaii, Jozef Stefan Inst.,

Kanagawa U., KEK,Krakow INP, U. Melbourne,

National Taiwan U., Niigata U., Nihon Dental U., Nova Gorica U.,

Osaka U., Princeton U., U. Sydney,Tohoku U., U. Tokyo,

Tokyo Inst. Tech., Tokyo Metropolitan U., Toyama NCMT, Vienna IHEP

The Belle SVD Group

~100 people

SVD Past and PresentSVD2 (Oct 2003 ～

)SVD1 (1999 ~ 2003 )

Unresolved issues• Rad. Hardness• Small acceptance

3 layers23o < < 139o

rmin = 3.0 cm2 kGy (2M Rad)

4 layers17o < < 150o

rmin = 2.0 cm200 kGy (20M Rad)

SVD1 SVD2 : Larger Acceptance

Coverage 84 91 %B0J/KS 14.4 15.8 events/fb-1

+10 % Higher Efficiency Achieved !

SVD1 SVD2 : Smaller Radius

~30% improvement for z-Vertex Resolution

SVD1 SVD2 : Radiation Tolerance

Layer 3

Layer 2

Layer 2(1.2m)Layer 1R

elat

ive

Gai

n

SVD1 ReadoutVA1 (0.8m)Rad. Tole. 2kGy

SVD2 Readout VA1TA (0.35m)Rad. Tole. 200kGy

No longer afraid of Radiation DamageNo replacement for SVD2 (>3 years)Gain of operation time is priceless

Belle IR dose0.2kGy/year

Layer 1

Layer 3

Layer 4

Layer 2

SVD Past and PresentSVD2 (Oct 2003 ～

)SVD1 (1999 ~ 2003 )

Unresolved issues• Rad. Hardness• Small acceptance

3 layers23o < < 139o

rmin = 3.0 cm2 kGy (2M Rad)

4 layers17o < < 150o

rmin = 2.0 cm200 kGy (20M Rad)

Higher efficiencyBetter resolutionStable operation efficiency

Unresolved issues• z trigger terminated

Beam BG (non-phys) event suppression

• Performance in higher Beam BG

Future prospects of Beam-BG

2000 2002 2004 2006

Peak Luminosity (/nb/sec)

Beam currents (A)

Higher Luminosity is providedby Higher Beam current

Higher Luminositywill be providedby the Higherbeam currents

Beam BG I2

Beam BG mayincrease x(2~3)

in 2008

SVD Past and PresentSVD2 (Oct 2003 ～

)SVD1 (1999 ~ 2003 )

Unresolved issues• Rad. Hardness• Small acceptance

3 layers23o < < 139o

rmin = 3.0 cm2 kGy (2M Rad)

4 layers17o < < 150o

rmin = 2.0 cm200 kGy (20M Rad)

Higher efficiencyBetter resolutionStable operation efficiency

Unresolved issues• z trigger terminated

Beam BG (non-phys) event suppression

• Performance in higher Beam BG

Layer1 Layer2

Layer3 Layer4

Occupancy

Hit

-fin

din

g E

fficie

ncy

High occupancyFake hitsCluster shape distortion

Current BG level Future BG level ?Degradation of Hit-finding Efficiency

Is there hitor not?

Degradation of Resolution

Occupancy (%)

Intr

insic

resolu

tion

(m

)

BG overlay MCB0J/KS

Intrinsic Resolution

BGx3residual (m)

residual (m)

SVD Past, Present and FutureSVD2 (Oct 2003 ～

)SVD1 (1999 ~ 2003 )

Unresolved issues• Rad. Hardness• Small acceptance

3 layers23o < < 139o

rmin = 3.0 cm2 kGy (2M Rad)

4 layers17o < < 150o

rmin = 2.0 cm200 kGy (20M Rad)

Software Efforts

in progress

Almost saturated

Unresolved issues• z trigger terminated

Beam BG (non-phys) event suppression

• Performance in higher Beam BG

SVD3from ’07

ThresholdShorter shaping timegives less occupancy

Occupancy Reduction in SVD3

~2000ns

VA1TATp~800ns

Threshold

~160ns

APV25Tp~50ns APV25 x4chip

VA1TA x4chip

Occupancy

shaping time ofreadout chip

Occupancy

~ 1/13

• Performance degradation is not serious for outer layers• Quick upgrade is necessary (~2007)Replace only for Layer 1 & 2Layer 3 & 4 are same as SVD2

APV25

VA1TA APV25Peaking time [ns] 800 40~200

Pulse width [ns] ~2000 ~160

Pipeline memory --- 192depths

Clock [MHz] 5 40

Sensor

Preamp + CRRC Shaper Multiplexing 　

Pipeline memory

FADC

Developed for CMS Si Tracker

waveform samplingTime window ~20ns

Further BG reduction

DSSD should be optimized for APV25

pTCNoise

Capacitive noise will be serious because of short Tp 800ns 50ns

(C : detector capacitance)

Reduction of Capacitance is Essential

VA1TA (Tp=800ns)

APV25 (Tp=50ns)

Nois

e (

en

c)

Detector Capacitance (pF)20 3010

500

1500

1000

Capacitance of SVD2 DSSD(r-)

DSSD optimization for APV25

SVD2 DSSD SVD3 DSSDz (p) r- (n) z (n) r- (p)

strip length (mm) 25.6 76.8 26.1 77.7strip/readout pitch (m) 75/150 50/50 76/152 25.5/51implant width (m) 50 24 24 10capacitance (pF) 3.8 22.5 4.7 9.4

S/N (VA1TA) 102 56 100 83S/N (APV25) 1st layer 52 17 48 33

S/N (APV25) 2nd layer 38 10 34 21

Floating Strips for r- side (flip pn strip)Reduction of strip width

Test sensors by HPK: DSSD x20 (2006), SSD(n-strip) (2005)

Beam Test (4GeV/c ) withAPV25 + VA1TA system

APV25+SSD(n-side)

Dec, 2005

SVD2 spare ladders x3

SVD2 ladder

SVD2 ladder

SVD2 ladder

APV25 ladder

Simultaneous operation succeededfor

APV25 system with SVD2 system

S/N of SSDtowards SVD3

S/N=34

Readout strip

Floating stripCharge Collection

Eff. = 81%

Beam test results 28.4mm( DSSD 26.1mm)

Laser Scan test for SVD3 DSSD

Laser 980nm

Sep, 2006

Double sided assemblyPoor bonding due to Kapton flex in R&D

z (n strip)

r- (p strip)

Laser scanresults (n-strip)

SSD

DSSD for SVD3

Charge CollectionEff. = 85%

Sep, 2006

Laser Scan results (p-strip)Sep, 2006

Due to poor bonding

Test in High BG area

Plan to start from Oct, 2006Operation with SVD2 spare ladderCheck performances Occupancy reduction, etc.

SVD3 mockup testSufficient clearance

is confirmed forthe larger Hybrid

NovOct

Schedule

DSSD

Hybrid

SepAugJulJunMayAprMarFebJanDec

2006 2007

full production

Production / test

Assembly

Jig prod. / test Layer 1 Layer 2 mount

Repeater

prod. / test Test w/ ladders

SY

STEM

TES

TIN

STALLATION

FADC Prod. / test

DAQ Prod. / testDesign

Finalizedsoon

Summary• The Belle SVD operated smoothly for the past

year• Degradation of performance due to high BG

Hit finding Efficiency (layer 1 & 2), Vertex Resolution Might be serious ~2008

• Upgrade plan (SVD3) to replace readout chip VA1TA APV25 (occupancy < 1/10) Replace only in Layer 1 and 2 (Layer 3 & 4 will be kept)

• DSSD is optimized for APV25 Short strip width to reduce capacitance noise Test sensors (DSSD & SSD) Beam test for SSD S/N~34 Simultaneous operation of APV25 system with SVD2 system Laser test full production was ordered from HPK

• We would like to upgrade SVD3 next year

backup

SVD3 mechanical issues

con

necto

rAPV25

65.3

31.0

3.0

4.0

Modifications are necessary because APV25 chip is wider than VA1TA

= 0.425

Requirements from PhysicsRequirements from Physics

t z c

High Efficiency ( ~90% )Good Resolution ( z ~ 100m )

electron(8GeV)

positron(3.5GeV)

(4S)resonance

+

-K+

-

0D

+

-

KS/L

J/

z ~ 200m

B0

B0_

B0 tag_B

0 tag

Asym. = -CPsin21sinmt