jan24-26, 2008bnm2008 atami, japan1 belle upgrade: tracking and vertexing t.kawasaki(niigata-u)
TRANSCRIPT
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Jan24-26, 2008 BNM2008 Atami, Japan 1
Belle upgrade:Tracking and Vertexing
T.Kawasaki(Niigata-U)
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Jan24-26, 2008 BNM2008 Atami, Japan 2
Introduction• High luminosity B factory
– High precision measurement with high statistics to search the new physics in B decays
• Many modes which are sensitive to new physics need– High Hermeticity – Good efficiency on Low momentum & Ks daughter tracking,
DB
KB
KKKKKB
S
SSS
,,
,,00
000 (tCPV)(tCPV)
Ks vertexing
Hermeticity
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Jan24-26, 2008 BNM2008 Atami, Japan 3
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
• Better Resolution (At least competitive performance as current SVD)– Thin sensor ( refer the next talk for material effect)⇒– Small BP radius
Belle SVD Hit finding eff. vs. Occ.
Occupancy
15%
By Fujiyama(TIT)
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Jan24-26, 2008 BNM2008 Atami, Japan 4
Super Belle detector (LoI ‘04)
SC solenoid1.5T
New readout and computing systems
Aerogel Cherenkov counter + TOF counter
/ KL detection 14/15 lyr. RPC+Fe tile scintillator
CsI(Tl) 16X0 pure CsI (endcap)
“TOP” + RICH
Tracking + dE/dx small cell + He/C2H6remove inner lyrs.
use fast gas
Si vtx. det. 4 lyr. DSSD 2 pixel/striplet lyrs. + 4 lyr. DSSD
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Jan24-26, 2008 BNM2008 Atami, Japan 5
Super Belle Vertex Tracker(LoI ‘04)
(cm)
r =150mm
Aim 1cm radius beam pipe
(cm
)
Two thin pixel layer
Slanted layer to keep acceptance, optimize incident angle and save detector size
6 sensor layers to make low momentum tracking
17°
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Upgrade Schedule
Stop Belle on the end of 2008 (JPY)
Start sBelle operation from the beginning of 2012
Along to the current upgrade schedule
We need REALISTIC upgrade plan for T=0 operation in 2012 ( with ~1035 )Further upgrade can be done after getting higher luminosity
2007 2008 2009 2010 2011 2012Stop Belle
Start sBelle
Reconstruction of detector takes 3 years⇒ We have only 1 year for R&D work!!
KEKB&Belle upgradeR&D
( 1cm beampipe, Thin Monolithic Pixel sensor …… needs further R&D work )
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Central Drift Chamber• Large cover area in radius
– 88~863 mm ⇒ 172~1118 mm• Inner part replaced by Si Tracker
– 50 58 layers⇒• Small cell to reduce occupancy
– ⇒ 2.5mm– 8k ⇒ 15k sense wires
• Same gas mixture :He + C2H6
• Fast FADC readout
CDC
•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)
Pt/Pt = (0.11~0.19)Pt 0.30/[%] :possible thanks to large cover in radius
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Silicon Vertex Tracker• Occupancy estimation
– Assuming Occ Tp, channel area, 1/r∝ 2
– 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
Shaper
・ 160 pipeline FIFO
⇒ pulse shape scan with 40MHz Clk
• Further BG reduction is possible
by Pulse shape and timing information
•32 step FIFO as event queues
•Deadtime free readout@ 10kHz trigger rate
0 100 200 ns ⇒ Standard rectangle DSSD is OK
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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
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Study on Detector configuration
CDC
SVDSVD
CDC
SVDSVD
SVD L1-L4 @ r = 2.0, 4.35, 7.0, 8.8 cmCDC r= 8.8 ~ 86.3cm
SVD Add L5&L6 @ r = (13), 14cmCDC r=16.0 ~ 112.0cm
Put 5&6 layer
Modify the current Belle simulator Use L4 ladder structure as L5&6 layer No sensor at forward region
Belle sBelle
Evaluate new detector configurationwith TRACKERR calculation & GEANT3 full simulation
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Impact Parameter resolution
r-direction z directionCalculated by TRACKERR
Occupancy effects. Degradation of intrinsic resolution is included. Efficiency loss is NOT included
Beampipe radius is importantCompetitive performance as the current SVD
LoI ‘04sBelleSVD2(now)
For
0.2GeV 0.5GeV 1.0GeV 2.0GeV
sin0 1.4
0.02
0.01
[cm]
0.03[cm]
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Jan24-26, 2008 BNM2008 Atami, Japan 12
Momentum resolution
resolution resolutionCalculated by TRACKERR
Competitive performance as the current SVDMore layer doesn’t worsen momentum resolution
LoI ‘04sBelleSVD2(now)
For
0.2GeV 0.5GeV 1.0GeV 2.0GeV
sin0 1.4
0.02
0.01
[rad][/MeV]
0.3
0.1
Refer the next talk about a material effect
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Ks reconstruction : 5th layer position
=0.68
Move 5th layer to outer
More Ks but poor B vtx resolution
Eff. Ks Ks Vtx resolution
)K(KB S* 00 GEANT3
Full simulationby Shinomiya(Osaka)
eff12sin
Ks
e- e+Beam profile
B vertex: Ks pseudo track+ Beam profile
Relative luminosity to measure Acp
Require SVD hitson 2 layers
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Requirement on S/N ratio
Noise performance depends on FE chip
VA1 @ Tp = 1s
enc [e-]= 180+ 7.5/Cd[pF]
⇒ Leakage current dominates
APV25 @ Tp = 50ns
enc [e-]= 246 + 36/Cd[pF]
⇒Detector capacitance is crucial
・ Assuming signal=MIP@300m Si・ Noise determined by Sensor Leakage current Detector Capacitance
3DSSDs are readouted via FLEX ⇒Chain readout makes large detector capacitance
3DSSDs:~60pF 630e- ⇒ 2500e-
sBelleBelle
(calculate Cd component only)
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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)
Noise
M.E.
All Layers Only 5&6 Layers
S/N degradation on the outer layer doesn’t affect to M.E. so much
CDCM.E.
SVT
Kalman filteringExtrapolate track from CDC
Noise 10 ×Typ.
10 ×Typ.
But, In case of Ks daughter track…
GEANT3Full sim.
Increase noise
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Jan24-26, 2008 BNM2008 Atami, Japan 16
r of Ks decay vertex
Matching efficiency for KsM
atch
ing
effi
cien
cy
Noise x 2
Noise x 4
normal
0
1.0
0 10 20 [cm]
SVD Matched track
r of Ks decay vertex
0 10 20 [cm]
SKB
M.E. for Ks daughters are affected by S/N degradationLose 20% (SVT) events with 4 times worse S/N
L3L4
L5
L3 L4 L5
Noise x 4normal
GEANT3Full simBy Nakagawa(Niigata)
Increase Noise on L5&L6 only
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Jan24-26, 2008 BNM2008 Atami, Japan 17
BG effect on physics analysis
• 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
B Eff Ratio-1
Nominal 56.8 % 0.0 %
×5 BG 56.0 % -1.5 %
×20 BG 49.0 % -13.8 %
With 40% shorter shaping
×20 BG 51.4 % -9.5 %
)()(/ SKJ )( 3KD,DDDD s***
B Eff Ratio-1
Nominal 6.48% 0.0 %
×5 BG 5.69% -12.2 %
×20 BG 2.28% -64.9 %
With 40% shorter shaping
×20 BG 3.86% -40.5 %
By Ozaki Preliminary
Total performance of CDC + SVD
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Jan24-26, 2008 BNM2008 Atami, Japan 18
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
• 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?
No more HPK DSSD. Micron? SINTEF? New activities in India, Korea
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Jan24-26, 2008 BNM2008 Atami, Japan 19
Status of R&D Activity • We have been working to prepare Pipeline readout sensor module
Hybrid card with 4 APV25 chipsOperated with 40MHz clock (Princeton)
FADC: 40MHz digitizationOnline sparsification with FPGA
Confirm the capability of online sparsification algorithmThe result will come soon
Beamtest done in KEK in Nov 2007in KEK Fuji testbeam line 3GeV electron
(Vienna)
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Chip on sensor with FLEX hybrid
Proposal by Vienna group
No Cooling Cooling with 13 water℃
Readout each DSSDby putting thinned FE chip on sensor
Cooling with water through carbon fiber tube (low material and good thermal
conduction)
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Jan24-26, 2008 BNM2008 Atami, Japan 21
Schedule for CDC/SVT upgrade
2007 2008 2009 2010 2011 2012Stop Belle Start sBelle
Design
NOT official one
CDC
SVT
Test
End Plate
Machining
Wire
strin
ging
Cosmic
Test
Installa
tion
&Final Test
Cablin
g/Tubing
Sensor ProductionDesign Test
Assemblin
g
Final Test
Installa
tion
R&D
R&D
Endring
&Beampipe
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Jan24-26, 2008 BNM2008 Atami, Japan 22
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!
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Jan24-26, 2008 BNM2008 Atami, Japan 23
Pixel sensor R&DItems to be achieved for High
luminosity B factory
1. Readout Speed2. Radiation Hardness3. Thin Detector4. Full-sized detector
・ 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.
20052.5mmx2.5mm 32x32 cells chip
2006 5mmx5mm 128x128 cells chip
SOIPIXKEK-OKI
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Jan24-26, 2008 BNM2008 Atami, Japan 24
Backups
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Jan24-26, 2008 BNM2008 Atami, Japan 25
Bkg & TRG rate in future
KEKB SuperB
Luminosity(1034cm-2sec-1)
~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)phys. origin
Bkg origin
0.40.2
0.2
1410
4Synchrotron radiationBeam-gas scattering (inc. intra-beam scattering)Radiative Bhabha
SVD CDC PID / ECL KLM
KEKBBkg
x10 Bkg
x20 Bkg
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Jan24-26, 2008 BNM2008 Atami, Japan 27
Hit rate
10KHz
Apr.-5th ,2005IHER = 1.24AILER = 1.7ALpeak = 1.5x1034cm-2sec-1
ICDC = 1mA
Main
Inner
Small cell
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Simulation Study for Higher Beam Background
by K.Senyo.
MC +BGx1 MC+BGx20
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Hit rate at layer 35 410I**2 + 1400*I + 80
0
200
400
600
800
1000
1200
1400
1600
0 0.2 0.4 0.6 0.8 1
HER Beam Current(A)
Hit
rat
e(H
z)
740I**2 + 470*I + 80
0
500
1000
1500
2000
2500
3000
0 0.5 1 1.5 2
LER Beam Current(A)H
it R
ate
(Hz)
IHER = 4.1A Hit rate = 13kHzILER = 9.4A Hit rate = 70kHz
Dec., 2003 : ~5kHzNow : ~4kHz
Dec.,2003
In total 83kHz
HER LER
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CDC : Main parameters
Present FutureRadius of inner boundary (mm) 77 160Radius of outer boundary (mm) 880 1140Radius of inner most sense wire (mm) 88 172Radius of outer most sense wire (mm) 863 1120Number of layers 50 58Number of total sense wires 8400 15104Effective radius of dE/dx measurement (mm) 752 978Gas He-C2H6 He-C2H6
Diameter of sense wire (m) 30 30
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Intrinsic Resolution vs. Occupancy
Intrinsic Resolution
Occupancy
residual residual
occupancy < 0.04 occupancy 0.3
At high occupancy,
cluster shape is 'distorted'
reconstructed cluster energy to be off
the residual distribution to be widened
S.Fratina
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Hit Efficiency vs. Occupancy
Layer1 Layer2
Layer3 Layer4
hit or not?
21
3 4
Layer No.
0% 30%Occupancy
1.0
0.6
Efficiency
Higher Occupancy ~ Lower Hit Efficiency
• Signal + background hitswider 'distorted' cluster
• Wrongly associated background cluster
Y.Fujiyama
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Occupancy (%)
1
10
100
1000
0 2 4 6
Radius (cm)
SVD1(1usec)SVD2(500nsec)
Occupancy problem at innermost layer• Estimate occupancy at Super B
– Occupancy at SVD2• At most, 10% in r =20mm for 1034/cm2/s
– Assuming Occ. = luminosity/r2
• r =15mm for 1035/cm2/s occupancy = 200%
Factor 40 of reduction is needed!!
• How can we reduce Occ.?– Assuming Occ. = sensitive area* shaping time – Short shaping time
• Tp=100ns is possible (Factor 8) (SVD2:VA1TA, Tp=800ns)
– Strip area should be small.• Area=pitch*length short strip• How to shorten a strip length by 1/5?
5%
L=1035/cm2/s
SVD2(800nsec)
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Jan24-26, 2008 BNM2008 Atami, Japan 3470mm
Striplet design• To shorten strip length, we propose new
type of DSSD– Arrange strips in 45 degrees. Strip le
ngth is shortened– Small triangle dead region exists.
• About 7 % in Layer1
– Striplet can survive up to 2×1035/cm2
/s (1036 needs pixel type sensor!)
ZZ
rφrφ
Tp=50ns
Striplet
5%
Dead region
14mm
10mm
SVD2(800nsec)S-VTX(100nsec)
U
V
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Prototype Striplet Sensor (HPK)2.
75m
m74.1mm
10.5
mm
8.5m
m
71.0 mm• Thickness:300m• Double sided
– P and N strips on N-bulk
– Incline strip by 45 degree.
– 1024 strips on each side
• Strip pitch = 51m in U-V direction.
(Pad spacing is 72m along sensor edge)
• Since sensor size is small, inactive region can’t be ignored
• How to reduce dead region• Check behavior near inactive
region carefully.
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Scan strips with IR laser
Laser position[m]
Sig
nal
(n
orm
aliz
ed)
sum
Laser position[m]
Sig
nal
(n
orm
aliz
ed)
sum
scan
P-side N-side
• Results– Striplet detector is functional.
– No signal on the triangle part• The edge of active region is so s
harp.
End of active region
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Matching efficiency Normal S/N
全層の S/Nを悪くしたとき
Noise x 5
Noise x 4
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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
Noise x 2
Noise x 4
normal
r of Ks vertex
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normal Noise x 2 Noise x 4 Noise x 10
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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 VTXResolution
Ks eff.
Mis-alignment doesn’t affect to efficiency
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FLEX hybrid/Chip on sensor
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22cm
46cm
Sensor Configuration Sensor Configuration (SVD1→SVD2)(SVD1→SVD2)
Z view
45cm
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SVD2: Ladder StructureSVD2: Ladder Structure
DSSDFLEX
Hybrid
Rib
Bridge
Lyr # in z # in BW FW
1 1 1 6
2 2 1 12
3 3 2 18
4 3 3 18
• VA1TA chip• 4 VA1TAs on a hybrid • 4analog signals read out i
n parallel• 128 channels/chip• 4 mW/channel
Number of channel: 128ch × 4 chips ×2 hybrid(/z)×2 hybrids(F/B) ×(6+12+18+18) Ladders = 110,592 Analog signals
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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
45ShaperInverterpreamp
192 stageAnalog Pipeline (4 µsec)
Analog output
Trigger
128 channel Multiplexer (3 µsec)
Noise= (246 + 36/pF) @50nsec
The silicon tracker development at KEK, Toru TSuboyama (KEK), 19 Dec. 2007 SILC meeting at Torino, Italy
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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.
• Proven in beam tests: Resolution ~ 2 nsec.• Reconstruction done in the FPGA chips in FADC board.
46
(HEPHY Vienna)
ShaperTrigger
The silicon tracker development at KEK, Toru TSuboyama (KEK), 19 Dec. 2007 SILC meeting at Torino, Italy
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Occupancy estimation
• 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)
L1 L2 L3 L4 L5 L6
x15BG
2x10^35
SVD310(%) 3 15 15 - -
SVD3mod10 3 1 1 <1 <1
SuperB<1 <1 3 1 <1 <1
x30BG
10^36
SVD320 6 30 30 - -
SVD3mod20 6 2 2 <1 <1
SuperB<1 <1 6 2 1 1
Assuming factor 3 for safety margin, in order to calculate helix resolution.
Assuming x15BG@2x10^35 , x30BG@10^36
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dr resolution
New CDC conf.TRACKERR V2.18
dr resolutoin
SuperBSVD3modSVD3
For 0.2GeV 0.5GeV 1.0GeV 2.0GeV
dr
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dz resolution
dz resolutoin
SuperBSVD3modSVD3
For 0.2GeV 0.5GeV 1.0GeV 2.0GeV
dz
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resolution
phi resolutoin
SuperBSVD3modSVD3
For 0.2GeV 0.5GeV 1.0GeV 2.0GeV
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tan resolution
tanl resolutoin
SuperBSVD3modSVD3
For 0.2GeV 0.5GeV 1.0GeV 2.0GeV
tan
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resolution
kappa resolutoin
SuperBSVD3modSVD3
For 0.2GeV 0.5GeV 1.0GeV 2.0GeV
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