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Silicon Vertex Detector at PHENIX

Atsushi TaketaniRIKEN / RBRC

1. Physics Goal

2. Detector Concept

3. Structure

4. Pixel detector

5. Strip detector

6. Summary

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Physics with Silicon Vertex TrackerPhysics with Silicon Vertex Tracker QCD at high temperature• Detail investigation of the hot and dense strongly interacting matter

– Energy loss of heavy quarks in the dense– Elliptic flow of heavy quarks– Open beauty production.– Accurate charm reference for quarkonium.– Determine QQ background of Thermal dilepton continuum – Improve Upsilon e+e- measurement

Spin structure of nucleon• Gluon spin structure of the nucleon

– Gluon polarization G/G with charm, beauty. – x dependence of G /G with -jet correlations. 

QCD in cold nuclei• Nuclear structure in nuclei

– Nuclear dependence of PDFs.

– Saturation physics:

– Gluon shadowing over broad x-rangeKey

wor

d = H

eavy

Qua

rk p

rodu

ction

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charm and bottom identification by displaced vertex

Jet identification with larger acceptance

PhysicsPhysics Goals: Gluon polarization Goals: Gluon polarization G(x)G(x)G

luon

Pol

ariz

atio

n

Gluon polarization can be measured by doule-spin asymmetry A_LL of direct photon and heavy quark production in polarized pp collisions

Jet + direct constraint on xg

Polarized p+p collisions

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Expected Performance

Layer radius Sensor Occupancy

Layer 1 2.5 cm Pixel 0.53 %

Layer 2 5.0 cm Pixel 0.16%

Layer 3 10.0 cm Strip 4.5 % (x-strip)

4.7 % (u-strip)

Layer 4 14.0 cm Strip 2.5 % (x-strip)

2.7 % (u-strip)

Expected occupancy at Au-Au 200GeV most central event Distance to the Closest Approach [cm]

D0 decay

Collision Vertex

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Gamma+jets

Q_ – jet_

dpT = 15 ⊕ 5.9pT % ))exp()(exp(

)),exp()(exp(

2

1

jetT

jetT

s

px

s

px

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What is Silicon Detector

electrode

electrode

P type

N type

Diode Sensor

Depletion Layer

Charged particle

+-

+

+

++

--

-

-

electron

ee e e e

h h h h h

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Feature of Silicon Detector

• High dE/dx ( ~ 2MeV /(g/cm^2) )– Solid state detector comparing to gas chambe

r -> thin detector

• Low e-h pair creation energy– 3.6 eV instead of 13.6 eV for gas chamber

• Available Technology by industry– Compact, fine pitch and precise– Huge number of read out channel – Cost performance per readout channel

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Details of sensor

Cross section

•Relatively small readout channel

#ch ~ (Surface area)^1/2

•1+1 dimensional readout

ghost hits on high occupancy

Strip

•Huge readout channel

#ch ~ Surface area•True 2 dimensional read out no ghost at all

Pixel

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Identifying long-lived particle

Polarized ProtonPolarized Proton

Charmed or Bottomed messon

Charmed meson 　 ~ 100m

Bottomed meson　 ~ 300m

Silicon detector

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Requirements for Vertex Tracker

• High precision tracking for displaced vertex measurement. 40m displaced vertex resolution, c ~ 100m(D), ~400m(B)

• Large coverage tracking capability with momentum resolution (||<1.2 , and full azimuthally with /P ~ 6%P)

• High charged particle density ‘dN/d’ ~ 700 @=0• High Radiation Dose ~3.3E12 Neutron/cm^2@10Years• High Luminosity @PP -> High rate readout• Low Material Budget <- avoid multiple scattering and photon c

onversion for electron measurement by outer detectors.

1232102 scm

Physics side

Environment side

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endcap VTX 1.2 < < 2.7

barrel VTX | < 1.2

NCC 0.9 < < 3.0

Provides displaced vertex & jet measurement over 2

HBD

NCC

VTX

Displaced vertex:VTX: silicon trackerFVTX: forward Si

Jet measurement:NCC: nose cone calorimeter Other detectors:HBD: hadron blind detectorMuon triggerPID in west arm

MuonTrig MuonTrig

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The PHENIX VTX groupThe PHENIX VTX group

• 92 people from 20 institutions as of 2006 May

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Structure Barrel region

• ||<1.2, almost 2 in

• Pixel sensor at inner 2 layers

• Strip sensors at outer 2 layers

Forward region

• 1.2<||<2.7, 2p in

• 4 layers of mini strip

(50 x 2000 to 11000 m)

• Trigger capable

Pixel

Strip

R=2.5 and 5cm

R=10 and 14cm

VTX Layer R1 R2 R3 R4

Geometrical dimensions

R (cm) 2.5 5 10 14

z (cm) 21.8 21.8 31.8 38.2

Area (cm2) 280 560 1960 3400

Channel count Sensor sizeR z (cm2)

1.28 1.36(256 × 32 pixels)

3.43 × 6.36(384 × 2 strips)

Channel size 50 425 m2 80 m 3 cm(effective 80 1000 m2)

Sensors/ladder 4 4 5 6

Ladders 10 20 18 26

Sensors 160 320 90 156

Readout chips 160 320 1080 1872

Readout channels 1,310,720 2,621,440 138,240 239,616

Radiation length(X/X0)

Sensor 0.22% 0.67 %

Readout 0.16% 0.64 %

Bus 0.28%

Ladder & cooling 0.78% 0.78 %

Total 1.44% 2.1 %

Pixel detector Strip detector

VTX parametersVTX parameters

BEAM

Strip

Pixel

Layer radius Detector Occupancy in Central Au+Au collision

1 2.5cm Pixel 0.53 %

2 5.0cm Pixel 0.16%

3 10.0cm Strip 4.5 % (x-strip) 4.7 % (u-strip)

4 14.0 cm Strip 2.5 % (x-strip) 2.7 % (u-strip)

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PIXEL (Sensor and Readout)

Pixel size( x z ） 　 50 µm x 425 µmSensor Thickness 200umr = 1.28cm, z = 1.36 cm (Active area)256 x 32 = 8192 channel / sensor4 sensor/ chip4 chip / stave

Readout by ALICE_LHCB1 chip

• Amp + Discriminator / channel

•Bump bonded( 2 dim. Soldering) to each pixel

•Running 10MHz clock ( RHIC 106nsec )

•Digital buffer for each channel > 4usec depth

•Trigger capability > FAST OR logic for each crossing

•4 event buffer after L1 trigger

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Pixel detector module• Sensor module consists of 4 ALICE Pixel readout chips

Bump-bonded to silicon sensor

Sensor

• Half stave is mounted on the support structure

Support structure + cooling

• Pixel BUS to bring data out and send control signal into the readout chip is mounted on the half stave

• Each detector module is built of two half staves,read out on the barrel ends

Half stavePixel BUS

Data

• One readout unit, half stave, made from two sensor modules

Full stave

22cm

1.4cm

ALICE LHCB1 chip

SensorSensor Module

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Pixel Readout Overview

Half stave

11cm45cm

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Bus structure

Power 50 m Al

GND 50 m Al

• 5 layers structure• GND, Power and 3 signal lines

Signal 2; (Vertical line)line connected withpixel chip with wire bonding

Signal 3; (Horizontal line) send signal to Pilot Module connected with vertical line with through hole

Signal-3 3 m Cu

Signal-2 3 m Cu

Signal-1 3 m Cu

Signal 1; (for Surface Mount Device)Signal-1, Signal-2, and signal-3 are connected with through hole

Line spacing; 70 m pitchMaterial Budget; Total ~ 0.26 %

< 240 µm

200 µm

(13 µm)

150 µm

Wire bonding

Final configuration sensor

Readout chip

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Pixel Ladder SPIROFEM

Readout pictures

Extender

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2. Set-up of the telescope• Three half staves

• Three SPIROs

• One FEM

• Two trigger scintillator

• Analysis software– DAQ– Data converter– Tracking code– Event display

Set-up of three layers

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Layer 1

Layer 2

Layer 3

chip 1 chip 2 chip 3 chip 4

chip 5 chip 6 chip 7 chip 8

chip 9 chip 10 chip 11 chip 12

Event# 200

columnrow

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Silicon Sensor Stripixel Concept • a-pixels are connected to form X-strips, and b-

pixels are connected to form stereo-angled (4.6o) U-strips

X strips (connect a-pixels)

a-pixels interconnect u strips (connect b-pixels)

b-pixels interconnect

Readout pulse height by ADC

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Sensor elements:

Pixels: 80 µm 1 mm, projective readout via

double metal XU/V “strips” of ~3 cm length.

Developed at BNL Instrumentation Gr.

Two strip-pixel arrays on a single-sided wafer of 500 µm thickness, with 384 + 384 channels on 3 x 3 cm2 area.

new design:

“lateral” SVX4 readout.

Made by Hamamatsu

Initial design:

“longitudinal” readout.

Made by SINTEF

Single sided

1+1 dimensional readout

( X and U direction)

3cm3cm sensor 2 / chip

768 X strip and 768 U strips/chip

Position resolution is 25m by test beam

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Prototype Detector Using HPK Sensor

•The 1st prototype detector– 625 μm thickness– Tested at BNL – ROC+RCM+FEM

prototype w/ SVX4 chips developed by ORNL

– Gluing/wire-bonding at RIKEN

Optical fiber + focuser

XYZ micro-stage

Bias line

Data + Control cables

Power cables

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• S/N ~ 20:1 for 625 μm thickness• Charge-sharing test w/ IR laser pulse injection

– Large spot size in the present setup– Focusing length (8 mm) was too

short to shine only one pixel in 625 μm thick sensor.

– The maximum focusing length available in the same company is 70 mm. Not enough.

• Planned: possible solution is to use a radioactive source, cosmic rays and beam.

IR Laser Tests Results

X-Strip U-Strip

Laser spot

U-Strip

X3R U3R

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R&D : Prototypes Sensors• 1st prototype sensor

– Spiral p+ electrode : 8 μm line, 5 μm gap, 3 turns

– Thickness : 400/250 μm– R/O chip: VA2 (analog multiplexer)– Tests w/ source & beam

•S/N: 17:1 for 400 μm thickness•2-D sensitivity need improvements.

• 2nd prototype sensor – Spiral p+ electrode : 5 μm line,

3 μm gap, 5 turns– Thickness : 400/500 μm– R/O chip: SVX4(CDF SVX4 hybrid)– Tests w/ nano-sec pulsed laser

•S/N: 14:1 for 500 μm thickness•Laser signals were seen

2nd prototype sensor

1st prototype sensor

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Radiation damage of stripixel sensor

eqV

I

PHENIX in RHIC2 for 10 years

Saturation of

circuit

15nA/strip

20 ℃

10 ℃

0 ℃

-10 ℃

Rikkyo

PHENIX IR

3.3E+12 [Neq/cm2]

for 1 year from 2009 ~3E+11 [Neq/cm2]

Operation temperature will be 0 deg C

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Summary

• PHENIX VTX will investigate many physics on both spin and heavy ion program of RHIC.

• Detector R&D and production is on going.

• VTX will be installed in 2009.

• You are welcome to visit our Lab@RIKEN.

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endcap VTX 1.2 < < 2.7

barrel VTX | < 1.2

NCC 0.9 < < 3.0

Provides displaced vertex & jet measurement over 2

HBD

NCC

VTX

Displaced vertex:VTX: silicon trackerFVTX: forward Si

Jet measurement:NCC: nose cone calorimeter Other detectors:HBD: hadron blind detectorMuon triggerPID in west arm

MuonTrig MuonTrig