Belle upgrade:
Tracking and Vertexing
T.Kawasaki(Niigata-U)
Jan24-26, 2008
BNM2008
Atami, Japan
1
Introduction
• High luminosity B factory
– High precision measurement with high statistics to search
the new physics in B decays
B 0  K 0 ,K 0 , K S K S K S (tCPV)
(tCPV)
B 0  K S  0
B   ,  , D
  
Ks vertexing
Hermeticity
• Many modes which are sensitive to new physics need
– High Hermeticity
– Good efficiency on Low momentum & Ks daughter tracking,
Jan24-26, 2008
BNM2008
Atami, Japan
2
Requirements for sBelle Tracker
•
•
•
Robust against high beam background
• We assume ×20 BG @2×1035
• Occ ~8% @the first layer of Belle SVD(r=2cm)
• Fine segmentation
• Fast pulse shaping & time slice information
• High trigger rate
• Need high speed & deadtime free readout
More tracking efficiency
– Hermeticity
– Shallow angle tracking. Low momentum tracking
– Ks reconstruction
Belle SVD
Hit finding eff. vs. Occ.
15%
Occupancy
By Fujiyama(TIT)
Better Resolution (At least competitive performance as current SVD)
– Thin sensor (⇒refer the next talk for material effect)
– Small BP radius
Jan24-26, 2008
BNM2008
Atami, Japan
3
Super Belle detector (LoI ‘04)
SC solenoid
1.5T
CsI(Tl) 16X0
g pure CsI (endcap)
 / KL detection
14/15 lyr. RPC+Fe
g tile scintillator
Tracking + dE/dx
small cell + He/C2H6
gremove inner lyrs.
use fast gas
New readout
and
computing
systems
Jan24-26, 2008
Aerogel Cherenkov counter
+ TOF counter
g “TOP” + RICH
BNM2008
Si vtx. det.
4 lyr. DSSD
g 2 pixel/striplet
JapanDSSD
lyrs.Atami,
+ 4 lyr.
4
Super Belle Vertex Tracker(LoI ‘04)
Two thin pixel layer
(cm)
Aim 1cm radius beam pipe
r =150mm
6 sensor layers to make
low momentum tracking
Jan24-26, 2008
17°
Slanted layer to keep acceptance,
optimize incident angle and save detector size
BNM2008
Atami, Japan
5
(cm)
Upgrade Schedule
Along to the current upgrade schedule
Stop Belle
2007
2008
R&D
2009
2010
2011
KEKB&Belle upgrade
2012
Start sBelle
Stop Belle on the end of 2008 (JPY)
Start sBelle operation from the beginning of 2012
Reconstruction of detector takes 3 years
⇒ We have only 1 year for R&D work!!
We need REALISTIC upgrade plan for T=0 operation in 2012 ( with ~1035 )
Further upgrade can be done after getting higher luminosity
（1cm beampipe, Thin Monolithic Pixel sensor …… needs further R&D work）
Jan24-26, 2008
BNM2008
Atami, Japan
6
Central Drift Chamber
• Large cover area in radius
– 88~863 mm ⇒ 172~1118 mm
• Inner part replaced by Si Tracker
– 50 ⇒ 58 layers
CDC
• Small cell to reduce occupancy
– ⇒ 2.5mm
– 8k ⇒ 15k sense wires
• Same gas mixture :He + C2H6
• Fast FADC readout
•Occupancy esitimation
–Hit rate : ~100kHz  ~5kHz(current) x 20
–Maximum drift time : 80-300nsec  Shorter than the current one
–Occupancy : 1-3%  100kHz X 80-300nsec = 0.01-0.03
•Momentum resolution(SVD+CDC)
sPt/Pt = (0.11~0.19)Pt  0.30/b[%] :possible thanks to large cover in radius
Jan24-26, 2008
BNM2008
Atami, Japan
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Silicon Vertex Tracker
• Occupancy estimation
– Assuming Occ ∝ Tp, channel area, 1/r2
– Current SVD VA1(Tp=800ns): ~8%@ 1st layer
L =2×1035 ⇒ 8% × 20BG = 160%!
• Ex)APV25 (developed for CMS Si Tracker)
– Tp=50ns ⇒ Factor 16 reduction is possible
・160 pipeline FIFO
⇒ pulse shape scan with 40MHz Clk
• Further BG reduction is possible
Shaper
by Pulse shape and timing information
•32 step FIFO as event queues
•Deadtime free readout@ 10kHz trigger rate
0
Jan24-26, 2008
100
200
ns
BNM2008
⇒ Standard rectangle DSSD is OK
Atami, Japan
8
SVT upgrade Strategy
• T=0 option (2012) for L = ~1035
– Keep beampipe radius of 1.5cm same as current one
– Current SVD configuration + 2 outer layers = 6layers
• Improve Ks efficiency. Replace CDC inner layers
• Similar design DSSD can be used
– Fast Shaping(~50ns) + Timeslice on FE chip
• Further upgrade for L >1035
– Smaller beampipe radius (r =1cm or less)
– Innermost (thin) Pixel layers
• Improve impact parameter resolution
Jan24-26, 2008
BNM2008
Atami, Japan
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Study on Detector configuration
SVD
L1-L4 @ r = 2.0, 4.35, 7.0, 8.8 cm
CDC
r= 8.8 ~ 86.3cm
Belle
SVD
Add L5&L6 @ r = (13), 14cm
CDC
r=16.0 ~ 112.0cm
sBelle
CDC
CDC
Put 5&6 layer
SVD
SVD
Evaluate new detector configuration
with TRACKERR calculation &
GEANT3 full simulation
Jan24-26, 2008
BNM2008
Modify the current Belle simulator
Use L4 ladder structure as L5&6 layer
No sensor at forward region
Atami, Japan
10
Impact Parameter resolution
Calculated by TRACKERR
r- direction
[cm]
z direction
[cm]
0.02
0.03
LoI ‘04
sBelle
SVD2(now)
For 
0.2GeV
0.5GeV
1.0GeV
2.0GeV
0.01
0
1.4
sinq
Beampipe radius is important
Competitive performance as the current SVD
Jan24-26, 2008
BNM2008
Occupancy effects.
Degradation of intrinsic resolution
is included.
Atami, Japan Efficiency loss is NOT included
11
Momentum resolution
 resolution
[rad]
0.02
[/MeV]
0.3
k resolution
Calculated by TRACKERR
LoI ‘04
sBelle
SVD2(now)
For 
0.2GeV
0.5GeV
1.0GeV
2.0GeV
0.01
0.1
0
1.4
sinq
Competitive performance as the current SVD
More layer doesn’t worsen momentum resolution
Jan24-26, 2008
BNM2008
Atami, Japan
Refer the next talk
about a material effect
12
Ks reconstruction : 5th layer position
B 0  K * ( K S  0 )
GEANT3
Full simulation
by Shinomiya
(Osaka)
Ks Vtx resolution
Eff. Ks
Require SVD hits
on 2 layers
Move 5th layer to outer
sin 2
eff
1
More Ks but poor B vtx resolution
=0.68
B vertex:
Ks pseudo track
+ Beam profile
Ks
eJan24-26, 2008
BNM2008
Relative
luminosity to measure
Acp
Beam profile
Atami, Japan
e
+
13
Requirement on S/N ratio
・Assuming signal=MIP@300m Si
・Noise determined by
Sensor Leakage current
Detector Capacitance
3DSSDs are readouted via FLEX
⇒Chain readout makes
large detector capacitance
Noise performance depends on FE chip
Belle
sBelle
VA1 @ Tp = 1s
APV25 @ Tp = 50ns
enc [e-]= 180+ 7.5/Cd[pF]
enc [e-]= 246 + 36/Cd[pF]
⇒ Leakage current dominates
⇒Detector capacitance is crucial
3DSSDs:~60pF
⇒
630e-
2500e(calculate Cd component only)
Jan24-26, 2008
BNM2008
Atami, Japan
14
Effect of poor S/N ratio on the outer layers
M.E. (Matching Efficiency)
= Prob.(SVD hits are found on at least 2 SVD layers)
Increase noise
CDC
M.E.
M.E.
GEANT3
Full sim.
SVT
Only 5&6 Layers
All Layers
Noise
Kalman filtering
Extrapolate track from CDC
10
×Typ.
Noise
10
×Typ.
S/N degradation on the outer layer doesn’t affect to M.E. so much
But, In case of Ks daughter track…
Jan24-26, 2008
BNM2008
Atami, Japan
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Matching efficiency for Ks
Increase Noise on L5&L6 only
B  K S 
SVD Matched track
1.0
Matching efficiency
normal
L3 L4
GEANT3
Full sim
By Nakagawa
(Niigata)
L5
L3
L4
Noise x 2
L5
Noise x 4
normal
Noise x 4
0
0
10
20 [cm]
r of Ks decay vertex
0
10
20 [cm]
r of Ks decay vertex
M.E. for Ks daughters are affected by S/N degradation
Lose 20% (SVT) events with 4 times worse S/N
Jan24-26, 2008
BNM2008
Atami, Japan
16
BG effect on physics analysis
Total performance of CDC + SVD
J / (  ) K S (   )


B Eff
Ratio-1
Nominal
56.8 %
0.0 %
×5 BG
56.0 %
×20 BG
49.0 %
B Eff
Ratio-1
Nominal
6.48%
0.0 %
-1.5 %
×5 BG
5.69%
-12.2 %
-13.8 %
×20 BG
2.28%
-64.9 %
With 40% shorter shaping
×20 BG
51.4 %
D* D* ( D*  D s , D  K 3 )
-9.5 %
With 40% shorter shaping
×20 BG
3.86%
Preliminary
-40.5 %
By Ozaki
• Major loss comes from low tracking efficiency for slow particles
• Efficiency loss on high multiplicity event is serious
– Moreover a pulse shape information CDC by FADC readout can save efficiency
– Gain by SVD standalone tracker is not included
Jan24-26, 2008
BNM2008
Atami, Japan
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Key technology for upgrade
• Timeslice Information/Full Pipeline readout
– Pipeline in FE chip (APV25, VA-modified, own ASIC)
• Practical implementation scheme in a limited space
– Ladder assembling. Mechanical Support structure
– Cooling/Cabling scheme
No more HPK DSSD.
Micron? SINTEF?
New activities in India,
Korea
• Save S/N for outer layer.
– FLEX readout. Chip on sensor
– Sensor development
• Low noise & Large area sensor is desirable
• Thin (less material)  Thick (more signal)
• Pixel sensor (Option for future upgrade)
– Thin & Fast readout. Monolithic device?
Jan24-26, 2008
BNM2008
Atami, Japan
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Status of R&D Activity
• We have been working to prepare Pipeline readout sensor module
Hybrid card with 4 APV25 chips
Operated with 40MHz clock (Princeton)
FADC: 40MHz digitization
Online sparsification with FPGA
(Vienna)
Beamtest done in KEK in Nov 2007
in KEK Fuji testbeam line 3GeV electron
Confirm the capability of
online sparsification algorithm
The result will come soon
Jan24-26, 2008
BNM2008
Atami, Japan
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Chip on sensor with FLEX hybrid
Proposal by Vienna group
Readout each DSSD
by putting thinned FE chip on
sensor
Cooling with water
through carbon fiber tube
(low material and good thermal
conduction)
No Cooling
Jan24-26, 2008
BNM2008
Atami, Japan
Cooling with 13℃ water
20
Schedule for CDC/SVT upgrade
Start sBelle
Stop Belle
2007
CDC
SVT
2008
2009
2010
Design
Design
2011
2012
Test
Sensor Production
Test
NOT official one
Jan24-26, 2008
BNM2008
Atami, Japan
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Summary
• We have started activity for the practical detector design for
Belle upgrade
– CDC
• Same gas mixture as Belle
• Better resolution with larger coverage in radius
• Reduce BG Occ. with small cell and time digitization
– SVT
•
•
•
•
R=1.5cm Beampipe + 6 DSSD layers
Employ Standard DSSD with short shaping (=50ns) for T=0
Competitive resolution as the current SVD
R&D of Pixel sensor should continue for the further upgrade
• Please join!! Any contributions are welcome!
Jan24-26, 2008
BNM2008
Atami, Japan
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Pixel sensor R&D
Items to be achieved for High
luminosity B factory
1.
2.
3.
4.
Readout Speed
Radiation Hardness
Thin Detector
Full-sized detector
SOIPIX
KEK-OKI
2005
2.5mmx2.5mm
32x32 cells chip
2006
5mmx5mm
128x128 cells chip
・MAPS is the unique solution.
・Development of MAPS (Monolithic Active Pixel sensor)
is in world wide competition (ex:CAPS(Hawaii), SOIPIX (KEK))
・It looks promising but needs more R&D for a few years
Progresses in the coming a few years are very important.
Jan24-26, 2008
BNM2008
Atami, Japan
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Backups
Jan24-26, 2008
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Atami, Japan
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Bkg & TRG rate in future
x20 Bkg
KEKB SuperB
Luminosity
~1
80
HER curr. (A)
LER curr. (A)
vacuum (10-7Pa)
1.2
1.6
~1.5
4.1
9.4
5
Bkg increase
-
x 20
TRG rate (kHz)
0.4
14
phys. origin
Bkg origin
0.2
0.2
10
4
(1034cm-2sec-1)
x10 Bkg
KEKB
Bkg
SVD
CDC PID / ECL KLM
Synchrotron radiation
Beam-gas scattering (inc. intra-beam scattering)
Jan24-26, 2008
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Atami, Japan
Radiative Bhabha
25
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Hit rate
Apr.-5th ,2005
IHER = 1.24A
ILER = 1.7A
Lpeak = 1.5x1034cm-2sec-1
ICDC = 1mA
Small cell
Inner
Main
10KHz
Jan24-26, 2008
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Atami, Japan
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Simulation Study for Higher Beam Background
by K.Senyo.
MC +BGx1
Jan24-26, 2008
BNM2008
MC+BGx20
Atami, Japan
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Dec.,2003
Hit rate at layer 35
410I**2 + 1400*I + 80
740I**2 + 470*I + 80
3000
1600
HER
1400
H it Rate(Hz)
1200
H it rate(Hz)
LER
2500
1000
800
600
2000
1500
1000
400
500
200
0
0
0
0.2
0.4
0.6
0.8
HER Beam Current(A)
1
0
0.5
1
1.5
LER Beam Current(A)
IHER = 4.1A Hit rate = 13kHz
Dec., 2003 : ~5kHz
ILER = 9.4A Hit rate = 70kHz
Now
: ~4kHz
In
total
83kHz
Jan24-26, 2008
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Atami, Japan
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2
CDC : Main parameters
Radius of inner boundary (mm)
Radius of outer boundary (mm)
Radius of inner most sense wire (mm)
Radius of outer most sense wire (mm)
Number of layers
Number of total sense wires
Effective radius of dE/dx measurement (mm)
Gas
Diameter of sense wire (m)
Jan24-26, 2008
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Atami, Japan
Present
77
Future
160
880
88
863
1140
172
1120
50
8400
752
58
15104
978
He-C2H6
30
He-C2H6
30
30
Intrinsic Resolution vs. Occupancy
Intrinsic Resolution
occupancy < 0.04
occupancy  0.3
residual
residual
At high occupancy,
g cluster shape is 'distorted'
g reconstructed cluster energy to be off
g the residual distribution to be widened
S.Fratina
g Occupancy
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Atami, Japan
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Hit Efficiency vs. Occupancy
Efficiency
Layer No.
hit or not?
1
Layer1
2
Layer2
1.0
Higher Occupancy
~ Lower Hit Efficiency
h
• Signal + background hits
g wider 'distorted' cluster
0.6
Layer3
3
Layer4
4
0%
g
30%
Occupancy
Jan24-26, 2008
BNM2008
• Wrongly associated
background cluster
Atami, Japan
Y.Fujiyama
32
Occupancy problem at innermost layer
• Estimate occupancy at Super B
–
L=1035/cm2/s
1000
Occupancy at SVD2
• At most, 10% in r =20mm for 1034/cm2/s
Occupancy (%)
– Assuming Occ. = luminosity/r2
SVD1(1usec)
SVD2(800nsec)
SVD2(500nsec)
• r =15mm for 1035/cm2/s
a occupancy = 200%
Factor 40 of reduction is needed!!
100
• How can we reduce Occ.?
– Assuming Occ.
= sensitive area* shaping time
– Short shaping time
• Tp=100ns is possible (Factor 8)
10
5%
Radius (cm)
(SVD2:VA1TA, Tp=800ns)
– Strip area should be small.
• Area=pitch*length a short strip
• How to shorten a strip length by 1/5?
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BNM2008
1
0
Atami, Japan
2
6
4
33
Striplet design
•
To shorten strip length, we propose new
type of DSSD
– Arrange strips in 45 degrees. Strip
length is shortened
– Small triangle dead region exists.
• About 7 % in Layer1
1000
Occupancy (%)
100
Tp=50ns
10
– Striplet can survive up to
2×1035/cm2/s
(1036 needs pixel type sensor!)
5%
Striplet
Radius (cm)
1
0
Z
SVD1(1usec)
SVD2(500nsec)
SVD2(800nsec)
S-VTX(50nsec)
S-VTX(100nsec)
With striplet
2
4
6
Dead region
U
rφ
10mm
14mm
70mm
Jan24-26, 2008
BNM2008
Atami, Japan
V
34
Prototype Striplet Sensor (HPK)
74.1mm
•
•
2.75mm
71.0 mm
– P and N strips on N-bulk
– Incline strip by 45 degree.
– 1024 strips on each side
8.5mm
•
10.5mm
Thickness:300m
Double sided
Strip pitch = 51m in U-V
direction.
(Pad spacing is 72m along
sensor edge)
•
•
•
Jan24-26, 2008
BNM2008
Atami, Japan
Since sensor size is small,
inactive region can’t be
ignored
How to reduce dead region
Check behavior near inactive
region carefully.
35
Scan strips with IR laser
• Results
– Striplet detector is functional.
– No signal on the triangle part
scan
End of active region
Signal (normalized)
Signal (normalized)
• The edge of active region is so
sharp.
P-side
sum
N-side
Laser position[m]
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Atami, Japan
sum
Laser position[m]
36
全層のS/Nを悪くしたとき
Matching efficiency
Normal S/N
Noise x 4
Noise x 5
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Ks vertexの分布
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KsイベントでのMatching efficiency の変化
normal
Noise x 2
Noise x 4
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BNM2008
r of
Ks vertex
Atami, Japan
39
normal
Jan24-26, 2008
Noise x 2
BNM2008
Noise x 4
Atami, Japan
Noise x 10
40
Mis-alignment effect
• Large VTX tracker makes difficulty on alignment.
Red: Perfectly aligned
Blue: 10um, 0.1mrad
Green: 20um, 0.2mrad
Pink: 30um, 0.3mrad
Ks VTX
Resolution
Ks eff.
Mis-alignment doesn’t affect to efficiency
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FLEX hybrid/Chip on sensor
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Sensor Configuration
(SVD1→SVD2)
45cm
22cm
Jan24-26, 2008
Z view
46cm
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SVD2: Ladder Structure
Rib
Bridge
FLEX
Lyr
Hybrid
DSSD
VA1TA chip
•
•
•
•
4 VA1TAs on a hybrid
4analog signals read
out in parallel
128 channels/chip
4 mW/channel
# in 
# in z
BW
FW
1
1
1
6
2
2
1
12
3
3
2
18
4
3
3
18
Jan24-26, 2008
•
BNM2008
Number of channel:
128ch × 4 chips
×2 hybrid(/z)×2 hybrids(F/B)
×(6+12+18+18) Ladders
= 110,592 Analog signals
Atami, Japan
44
Readout with APV25 ASIC
• APV25 is chosen
–Originally developed for CMS Silicon tracker
• Operated with 40MHz clock
–192 stage pipeline (~4 µsec trigger latency)
–Up to 32 readout queues
–128 ch analog multiplexing (3 µsec@40 MHz)
–Dead time: negligible at expected trigger rate of 10
kHz
Noise= (246 + 36/pF) @50nsec
Trigger
Analog
output
192 stageAnalog
128 channel
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Japan
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Shaper
Pipeline (4 µsec)
preamp
(3 µsec)
Inverter
The
silicon tracker development at KEK, Toru TSuboyama (KEK), 19 Dec. 2007Multiplexer
SILC meeting at Torino,
Italy
45
•
Hit timing reconstruction
B-Factory --> 2 nsec bunch crossing
– APV25 deconvolution filter can not be used.
•
Hit time reconstruction
– Proposed by Vienna group
– Read out 3, 6 … slices in the pipeline for one trigger.
– Extract the hit timing information from wave form.
Trigger
•
•
Shaper
Proven in beam tests: Resolution ~ 2 nsec.
Reconstruction done in the FPGA chips in FADC board.
Jan24-26, 2008
BNM2008
Atami, Japan
(HEPHY Vienna)
46
The silicon tracker development at KEK, Toru TSuboyama (KEK), 19 Dec. 2007 SILC meeting at Torino, Italy
46
Occupancy estimation
Assuming x15BG@2x10^35 , x30BG@10^36
SVD3
x15BG
2x10^3
5
SVD3mod
SuperB
SVD3
x30BG
10^36
SVD3mod
SuperB
L1
10(%)
10
<1
20
20
<1
L2
3
3
<1
6
6
<1
L3
15
1
3
30
2
6
L4
15
1
1
30
2
2
L5
<1
<1
<1
1
L6
<1
<1
<1
1
• Int res= x1.5(1.2) for 30%(10%) occupancy
• Occupancy ∝ 1/r2 × sensor aread
• Hit efficiency loss is not considered. (-10% for 30% Occ)
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Assuming
factor 3 for safety
margin, in order
to calculate helix resolution.
dr resolution
dr resolutoin
dr
SuperB
SVD3mod
SVD3
For 
0.2GeV
0.5GeV
1.0GeV
2.0GeV
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New CDC conf.
TRACKERR V2.18
dz resolution
dz resolutoin
dz
SuperB
SVD3mod
SVD3
For 
0.2GeV
0.5GeV
1.0GeV
2.0GeV
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 resolution
phi resolutoin

SuperB
SVD3mod
SVD3
For 
0.2GeV
0.5GeV
1.0GeV
2.0GeV
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tanl resolution
tanl resolutoin
tanl
SuperB
SVD3mod
SVD3
For 
0.2GeV
0.5GeV
1.0GeV
2.0GeV
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k resolution
kappa resolutoin
k
SuperB
SVD3mod
SVD3
For
0.2GeV
0.5GeV
1.0GeV
2.0GeV
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