Belle SVD status & upgrade plans O. Tajima (KEK) Belle SVD group

KEKB : the highest luminosity in the world 3.5 GeV e +  8.0 GeV e  e + e    (4S) with  = mrad crossing angle Located in Tsukuba, Japan L peak = (1.65  )/cm 2 /sec  ~ 1M BB pairs/day integrated luminosity = 0.63 /ab _ Belle detector

Belle Detector K L  detector 14/15 layer RPC+Fe Electromagnetic Calorimeter CsI(Tl) 16X 0 Aerogel Cherenkov Counter n = 1.015~1.030 TOF counter 3.5 GeV e + Central Drift Chamber momentum, dE/dx 50-layers + He/C 2 H 6 charged particle tracking K/  separation Si Vertex Detector ( SVD ) 4-layer DSSD B vertex Muon / K L identification ,  0 reconstruction e +-, K L identification 8.0 GeV e -

SVD Group Frankfurt 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 Present SVD2 (Oct 2003 ～ ) SVD1 (1999 ~ 2003 ) Unresolved issues Rad. Hardness Small acceptance 3 layers 23 o <  < 139 o r min = 3.0 cm 2 kGy (2M Rad) 4 layers 17 o <  < 150 o r min = 2.0 cm 200 kGy (20M Rad)

SVD1  SVD2 : Larger Acceptance Coverage 84  91 % B 0  J/  K S 14.4  15.8 events/fb % Higher Efficiency Achieved !

SVD1  SVD2 : Smaller Radius ~30% improvement for z-Vertex Resolution

SVD1  SVD2 : Radiation Tolerance Layer 3 Layer 2 (1.2  m) Layer 1 Relative Gain SVD1 Readout VA1 (0.8  m) Rad. Tole. 2kGy SVD2 Readout VA1TA (0.35  m) Rad. Tole. 200kGy No longer afraid of Radiation Damage No replacement for SVD2 (>3 years) Gain of operation time is priceless Belle IR dose 0.2kGy/year Layer 1 Layer 3 Layer 4 Layer 2

SVD Past and Present SVD2 (Oct 2003 ～ ) SVD1 (1999 ~ 2003 ) Unresolved issues Rad. Hardness Small acceptance 3 layers 23 o <  < 139 o r min = 3.0 cm 2 kGy (2M Rad) 4 layers 17 o <  < 150 o r min = 2.0 cm 200 kGy (20M Rad) Higher efficiency Better resolution Stable operation  efficiency Unresolved issues z trigger  terminated Beam BG (non-phys) event suppression Performance in higher Beam BG

Future prospects of Beam-BG Peak Luminosity (/nb/sec) Beam currents (A) Higher Luminosity is provided by Higher Beam current Higher Luminosity will be provided by the Higher beam currents Beam BG  I 2 Beam BG may increase x(2~3) in 2008

SVD Past and Present SVD2 (Oct 2003 ～ ) SVD1 (1999 ~ 2003 ) Unresolved issues Rad. Hardness Small acceptance 3 layers 23 o <  < 139 o r min = 3.0 cm 2 kGy (2M Rad) 4 layers 17 o <  < 150 o r min = 2.0 cm 200 kGy (20M Rad) Higher efficiency Better resolution Stable operation  efficiency Unresolved issues z trigger  terminated Beam BG (non-phys) event suppression Performance in higher Beam BG

Layer1 Layer2 Layer3 Layer4 Occupancy Hit-finding Efficiency High occupancy  Fake hits  Cluster shape distortion Current BG level Future BG level ? Degradation of Hit-finding Efficiency Is there hit or not?

Degradation of Resolution Occupancy (%) Intrinsic resolution (  m) BG overlay MC B 0  J/  K S Intrinsic Resolution BGx3 residual (  m)

SVD Past, Present and Future SVD2 (Oct 2003 ～ ) SVD1 (1999 ~ 2003 ) Unresolved issues Rad. Hardness Small acceptance 3 layers 23 o <  < 139 o r min = 3.0 cm 2 kGy (2M Rad) 4 layers 17 o <  < 150 o r min = 2.0 cm 200 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 SVD3 from ’07

Threshold Shorter shaping time gives less occupancy Occupancy Reduction in SVD3 ~2000ns VA1TA Tp~800ns Threshold ~160ns APV25 Tp~50ns APV25 x 4chip VA1TA x 4chip Occupancy shaping time of readout chip Occupancy ~ 1/13 Performance degradation is not serious for outer layers Quick upgrade is necessary (~2007)  Replace only for Layer 1 & 2  Layer 3 & 4 are same as SVD2

APV25 VA1TAAPV25 Peaking time [ns]80040~200 Pulse width [ns]~2000~160 Pipeline memory---192depths Clock [MHz]540 Sensor Preamp + CRRC Shaper Multiplexing Pipeline memory FADC Developed for CMS Si Tracker waveform sampling Time window ~20ns Further BG reduction

DSSD should be optimized for APV25 Capacitive noise will be serious because of short T p 800ns  50ns (C : detector capacitance) Reduction of Capacitance is Essential VA1TA (T p =800ns) APV25 (T p =50ns) Noise (enc) Detector Capacitance (pF) Capacitance of SVD2 DSSD(r-  )

DSSD optimization for APV25 SVD2 DSSDSVD3 DSSD z (p) r-  (n) z (n) r-  (p) strip length (mm) strip/readout pitch (  m) 75/15050/5076/ /51 implant width (  m) capacitance (pF) S/N (VA1TA) S/N (APV25) 1 st layer S/N (APV25) 2 nd layer Floating Strips for r-  side (flip p  n strip) Reduction of strip width Test sensors by HPK: DSSD x20 (2006), SSD(n-strip) (2005)

Beam Test (4GeV/c   ) with APV25 + VA1TA system APV25+SSD(n-side) Dec, 2005 SVD2 spare ladders x3

SVD2 ladder APV25 ladder Simultaneous operation succeeded for APV25 system with SVD2 system

S/N of SSD towards SVD3 S/N=34 Readout strip Floating strip Charge Collection Eff. = 81% Beam test results 28.4mm (  DSSD 26.1mm)

Laser Scan test for SVD3 DSSD Laser 980nm Sep, 2006 Double sided assembly Poor bonding due to Kapton flex in R&D z (n strip) r-  (p strip)

Laser scan results (n-strip) SSD DSSD for SVD3 Charge Collection Eff. = 85% Sep, 2006

Laser Scan results (p-strip) Sep, 2006 Due to poor bonding

Test in High BG area Plan to start from Oct, 2006 Operation with SVD2 spare ladder Check performances Occupancy reduction, etc.

SVD3 mockup test Sufficient clearance is confirmed for the larger Hybrid

NovOct Schedule DSSD Hybrid SepAugJulJunMayAprMarFebJanDec full production Production / test Assembly Jig prod. / test Layer 1Layer 2mount Repeater prod. / test Test w/ ladders SYSTEM TEST INSTALLATION FADC Prod. / test DAQ Prod. / test Design Finalized soon

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

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SVD3 mechanical issues connector APV Modifications are necessary because APV25 chip is wider than VA1TA

 = Requirements from Physics High Efficiency ( ~90% ) Good Resolution (  z ~ 100  m ) electron (8GeV) positron (3.5GeV)  (4S) resonance ++ -- K+K+ --  ++ -- K S/L J/   z ~ 200  m B0B0 B0B0 _ B 0 tag _ Asym. = -  CP sin2  1 sin  m  t