Detector Upgrade from Belle to Belle II

Workshop on Synergy between High Energy and High Luminosity Frontiers. January 10-12, 2011Tata Institute of Fundamental Research, Mumbai, India

Detector Upgrade from Belle to Belle II

Toru Tsuboyama (KEK) 12 Jan. 2011

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The purpose of the B factories Explore the CP violation of B meson decay through the

particular decay chain e+ e– ϒ(4S) Bo Bo (CP mode decay) + (tag mode decay) ϒ(4S) decays into a coherent Bo Bo pair. Only the vertices of Bo and Bo can be measured.

No particles from the decay vertex of ϒ(4S). The tasks of a B factory detector:

Record the B meson decay reactions as efficient as possible. Identify the B and B in the final state. Measure the decay position of B and B mesons. Combining these information, investigate the difference of

particles and antiparticles.

SEL 2011 meeting at Mumbai T.Tsuboyama

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Method of CP violation measurement

S: mixing induced CP parameterSEL 2011 meeting at Mumbai T.Tsuboyama

electron(8GeV)

electron(3.5GeV)

ϒ(4S)resonance B1

B0

CP mode decay

B2

B0

t2 t1 m+

m -

D0 p+

p+

K–

m-

bg = 0.425DZ~200mm

n Tag mode decay

)sin())(())((

))(())((00

00

tmSA dftBftB

ftBftBCP

CPCP

CPCP DDD+D

D-D

Ks

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m / KL detector 14/15 lyr. RPC+Fe

Central Drift Chamber small cell +He/C2H6

CsI(Tl) 16X0

Aerogel Cherenkov Counter n=1.015~1.030

Silicon Vertex detector 4 layer silicon strip sensors

TOF conter

Super conducting solenoid 1.5T

8 GeV e-

3.5 GeV e+

Belle Detector

st = 95 ps

s/E=1.8%@1 GeVEid eff=30 % (0.1% fake)

Kid eff = 90 % (6% fake)

(spt/pt)2 [%2] = (0.19 pt)2+(0.34)2

Muon ID eff>90 % (2% fake) s(Dz) = 100 mmSEL 2011 meeting at Mumbai T.Tsuboyama

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Belle Detector

Tasks SVD CDC TO

F ACC CsI KLMTRGDAQ

CMP

Record the B meson Events Efficiently ✔

Full reconstruction of B meson

Tracking ✔ ✔Calorimetry ✔Particle ID ✔ ✔ ✔ ✔ ✔

Measure the decay vertex position of B mesons ✔ ✔

B flavor Tagging (Particle ID) ✔ ✔ ✔ ✔ ✔

High performance data processing: ✔


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The adopted technology Full reconstruction of B meson

Tracking: Central Drift Chamber and Uniform Solenoid field.

Calorimetry: CsI(Tl) for good energy resolution. Particle Identification: dE/dx in CDC, TOF, Aerogel

Cerenkov counters (Barrel/Forward), KL/MU detector in the return yoke.

B flavor tagging bc + lepton: Lepton identifications by E/p, dE/dx,

KL/MU: bcs: Kaon identifications by ACC/TOF and BD* X, D* pD: Slow pions reconstruction by CDC.


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The adopted technology Measurement of the positions of two B decay

vertices. Asymmetric Energy e+e– collider.

The B mesons travel significant distance in the laboratory frame before decay.

The decay time of B can be measured by the respective decay position.

Silicon vertex detector The sensors are placed at 18 mm from the beam

collision point. The intrinsic position resolution is 5-10 mm. B meson decay vertices are reconstructed with enough

position resolution.SEL 2011 meeting at Mumbai T.Tsuboyama

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More physics channels

As the B factory detector is general purpose, we can explore following modes with high precision and high statistics. Other important channels

B tn, B KsKsKs, BKsp0g … B+/B–, charmed mesons, baryons Leptons especially t. Two photon processes. New baryon/meson states


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Why Belle should be upgraded? To accommodate 8x1035 /cm2/sec luminosity.

Belle was designed for 1x1035 /cm2/sec. Physics rate amounts to 10 kHz Beam background increases accordingly. Beam energy asymmetry 8+3.5 GeV 7+4GeV

To Improve the detector performances Better Tracking:

Beam pipe radius: 1.5cm 1.0 cm Inner radius of vertex detector: 1.8 cm 1.3 cm Outer radius of CDC 863 cm 1111 cm

Better PID performance Threshold Cherenkov Ring image Cherenkov


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The Belle detector upgrade


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IR (Interaction Region)


SC Quads

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Beam Pipe The nano-beam option

The beam is squeezed to 60 nm thick at the collision point. Beam current: 1.2 A 2.6 A(HER), 1.6 A 3.6 A(LER) The beam pipe radius is reduced from 1.5 cm to 1 cm. The e+ and e– beams collide with crossing angle, 83 mrad.

The two beams are separated significantly at 50 cm from the collision point. The beam pipe will have a crotch.


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Silicon Vertex detector


Belle Belle2Beam pipe Radius (cm)

1.5 1.0

Vertex detector Radius (cm)

1.8 < R < 9.6

1.4 < R < 14,0

Layers 4 layer DSSD 2 Layer Pixel + 4 layer DSSD

Background hit occupancy reduction APV25 ASIC with faster shaping time. Pixel detector in the first 2 layers Smaller

sensitive area per readout. Improve physics performance

Vertex reconstruction and resolution Recover the smaller energy asymmetry. Sensor at smaller radius. Lager acceptance for Ks vertexing.

larger radius.

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DEPFET pixel detector 2 layer DEPFET pixel detector Located at R=14 mm and 22 mm. The sensor are thinned to 50 mm

thick, in contrast to the hybrid pixel sensors (>500 mm thick, including sensor, readout chip, cables and cooling).


• The DEPFET group originally started the R&D for the ILC vertex detector.

• Converting from ILC design to Belle2 design is a challenge.

Synergy

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DEPFET pixel detector The charge collected in each

pixel is scanned by external clocks and sent to subsequent signal processing ASICs.

Reduction of huge data size due to background hits is a big challenge.


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Silicon strip vertex detector 4 layer with double-

sided silicon strip detectors.

3.8 cm < R < 14.0 cm


Layer R (mm) Ladders

Sensors

RO chips

3 38 8 16 850

4 80 10 30 560

5 115 14 56 300

6 140 17 85 192

Sum 49 187 1902

SEL 2011 meeting at Mumbai T.Tsuboyama17

Silicon strip vertex detector 3 types of DSSD sensors are

used. Made from 6” (15 cm) diameter

wafers, that became popular in the constructions of silicon trackers for Atlas, CMS, LHCb.

DSSD Large Wedge Small

Dimension (mm2)

124.88x59.6 125.58x(41.0-60.63)

124.88x40.4

# strips (p) 768/1535 768/1535 768/1535

# strips (n) 511/1023 511/1023 768/1535

Strip pitch (p) 75 50-75 50

Strip pitch (n) 240 240 160

Synergy

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Working with a foundry in Bangalore. Double sided detector prototypes have been produced. For the first time truly Microstrip Detector developed in India.

Activity at Tata Institute

On 300 mm thin n-type bulk silicon wafer of 4-inch diameterA clean room in Tata institute

for the sensor characterization


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Fourth Batch : <111>, 2 to 4 kΩ-cm Single sided Microstrip Detectors, 1024 Strips Two different processing cycles Delivered : March 2009 < 1 nAm per strip (Meets the specification)

0

0.5

1

1.5

2

2.5

3

3.5

4

0 100 200 300 400

curre

nt ( µ

amps

)

Reverse voltage ( volts )

I - V characteristics of SSD

8004-5*8018-1*8018-2*8018-38004-78004-8

Better Photolithography

Double Level

Single Level

Two class of processings

Performance (I)


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P – side response N – side response

Rise-time 5ns

Performance (II) Response to 1064nm pulsed laser Directly observed with an oscilloscope Expected responses are observed.


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Silicon strip vertex detector Readout chip: APV25 developed for

the CMS Silicon tracker. Its 192 stage pipeline and dead-time

free readout fits the Belle2 DAQ scheme.

Belle2 group utilizes the analog data in the pipe line for a wave form fit. A 100 times background rejection compared with Belle SVD is expected.


Synergy

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Central Drift Chamber Small cell structure and improved

readout electronics for immunity against high background rate.

Longer lever arm for better track momentum resolution, thanks to thinner Particle ID device.

14,336 sense wires and 42,240 field wires.


Belle Belle2

Radius of Inner Cylinder (mm)

77 160

Radius of Outer Cylinder (mm)

880 1130

Radius of innermost wire (mm)

88 168

Radius of outer most wire (mm)

863 1111

Number of Layers 50 56Number of sense wires 8,400 14,33

6

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Central Drift chamber The new electronics has been designed and

tested. The drift time is measured with a TDC built-in in

an FPGA. A slow FADC (around 30MHz) measures the

signal charge.


s~100mm

HV (kV)

X-T relation

Residual distribution

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Particle ID


Belle/Belle2 has the CsI calorimeter for full acceptance 15<q<150o. In order to keep its hermeticity, Belle adopted Threshold Aerogel Cherenkov counter for K/p separation. Thanks to recent developments of new type photo tubes, ring image Cherenkov Counters can be installed to Belle2. Significant improvement of K/p separation is

expected.

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TOP: Barrel Cherenkov counter Time of Propagation Counter:

The Cherenkov angle of radiated photons is measured with position (X, Y) and detection timing T.


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TOP: Barrel Cherenkov counter The Cherenkov angle

of radiated photons is measured with position (X, Y) and detection timing T.

Prototype quartz bar


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TOP: Barrel Cherenkov counter Square-shape multi-anode MCP-PMT

Multi-alkali photo-cathode Single photon detection Fast raise time: ~400ps Gain=1.5x106 (B=1.5T) T.T.S. (single photon): ~35ps (B=1.5T) Position resolution: <5mm


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ARICH: Forward Ring Image Cherenkov counter

Proximity focusing Cerenkov counter with: 2 layer Aerogel photon

radiators Readout with Pixilated HADP


Package size

72x72x30 mm3

Pixels 12x12Pixel size 4.9x4.9 mm2

Effective are

67 %

QE (typical) 25 %Gain ~ 105

Mass 220 g

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CsI Calorimeter Extrapolation of

background of Belle Present status: Energy

deposit in random event: 0.5 MeV/Crystal or 3 GeV/ECL.

“Probably” proportional to Beam current

3–10x background in Super KEKB.

Fine segment in time will be necessary


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CsI Calorimeter Upgrade Plan:

The CsI (Tl) of present Belle is used again. Shorten shaping time from 1μs to 0.5μs Waveform sampling (18 bit, 2 MHz) On board waveform fitting with FPGA.


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CsI Calorimeter Physics simulations show the performance is close to

that of the ultimate upgrade with pure CsI crystals readout with PMT. Cases Efficiency

Current Belle 12.4 ± 0.2 %

Current Belle with 10x BG

7.8 ± 0.2 %

DAQ upgrade 12.0 ± 0.2 %

(Pure CsI + PMT readout )

12.3 ± 0.2 %

# BKG hits in B tn

+ DAQ upgrade+ Pure CsI + PMT Eth (MeV)

B J/ΨKs, Ks p0p0 has two p0 reconstructed. CsI performance is essential. B tn requires no activities in CsI except for t decay particles. Sensitive to beam background.


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KLM: KL and m detector Belle RPC (resistive plate

chamber): hit rate < 1Hz/cm2

Endcap part will be replaced with Scintiilator + MPPC (SiPM)

Layer

Barrel

Forward

Backward

0 3.6 2.4 3.41 2.3 2.4 2.92 1.6 2.4 2,83 1.1 2.0 2.84 0.67 2.2 2.85 0.60 2.7 2.96 0.63 2.7 1.57 0.43 3.3 2.68 0.73 3.1 3.09 0.47 3.9 2.810 0.29 4.7 3.511 0.39 5.3 3.012 0.44 3.7 NA13 0.42 NA NA14 0.48 NA NA

Hit rate (Hz/cm2) expected of KLM at SuperKEKB

R3150

R1305

Longest strip

2820 mmSEL 2011 meeting at Mumbai T.Tsuboyama

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KLMHPK 1.3×1.3 mm 667 pixels

Vladimir (Russia)(used in T2K ND)

Kuraray Y11 MCNo other competative option High efficiency; long atten. length


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Trigger The collision luminosity will

be 40 times larger than the present Belle experiment.

Physics event rate will be 10 kHz at 8x1035/cm2/s.

The trigger system should be tunable to accommodate the physics rate for given DAQ and computing performances.


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DAQ At the full luminosity, the data rate amounts

to 600 MB/sec. A high performance DAQ system is

designed.

Belle Belle2

Level 1 Trigger

Trigger rate (kHz)

0.3-0.5 20-30

Event size (k Byte) 40 300

Data rate (MB/s) 20 6000

High Level Trigger

Reduction 1/ 2 1/10Storage Band Width (MB/s)

20 600 SEL 2011 meeting at Mumbai T.Tsuboyama

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Computing Belle computing resource is concentrated to

KEK. Belle2 50-100x larger computation power

and storage is necessary Highly distributed computing environment: GRID with help of CLOUD is necessary. GRID technology established by LHC computing

will be utilized.


Synergy

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Computing Belle computing resource is concentrated to

KEK. Belle2 50-100x larger computation power

and storage is necessary Highly distributed computing environment: GRID

with help of CLOUD is necessary.


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Belle2 detectorPID: New Cherenkov DetectorsBarrel: Time of Projection counterForward: Aerogel RICH counter

Vertex detector:2 layer DEPFET pixel detector4 layer Si vertex detector

Central Drift ChamberSmall cell layout

KL/m detector: Barrel: RPCEnd cap: Scintillator readout with MPPC

CsI(Tl) with wave sampling readout

COMP: High performance computer systems

TRG/DAQ: New Dead time free readout

(s/E)2 = (0.2/E)2+(1.6/√E)2 +(1.2)2 %2 Eid eff=30 % (0.1% fake)

TOP: Kid eff = 99 % (1 % fake)ARICH: Kid eff = 96 % (1 % fake)

(spt/pt)2 = (0.1 pt)2+(0.3)2 %2

(with SVD)

Muon ID eff>90 % (2% fake)

Impact parameter resolution sz = 20 mmSEL 2011 meeting at Mumbai T.Tsuboyama

Belle II Collaboration http://belle2.kek.jp

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13 countries/regions, 53 institutesSEL 2011 meeting at Mumbai T.Tsuboyama

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Summary The Super KEKB is approved. Improve the detector performances

Capability for data acquisition of 8x1035 luminosity. Immunity to expected 30x beam background Beam pipe radius: 1.5 cm 1.0 cm Vertex detector: 4Layer DSSD 4Layer DSSD + 2layer

DEPFET Lever arm of Vertex Detector + CDC: 210 cm 250 cm PID: Threshold Cherenkov Ring image Cherenkov. KID

efficiency (Barrel): 90 % 99 %. Disintegration of Belle2 has started Oct. 2010 Commissioning of Belle2: 1 October 2014.


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Belle upgrade started Dismantling of Belle detector components Central Drift chamber on 6 Jan 2011


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And more …. We still need more human resources or

collaborating institutes to construct our detector and stable operations.

We welcome new group to join Belle 2. Please contact our spokes persons if you are

interested.

Thank you for attention!


Detector Upgrade from Belle to Belle II

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