Spin Physics Capabilitywith Silicon Vertex Tracker for PHENIX

Maki Kurosawa (RIKEN)for the PHENIX Collaboration

BNL, CNRS-IN2P3, Columbia Univ. Nevis Labs, Ecole Polytechnique, ISU, KEK, LANL, ORNL, RBRC RIKEN, Rikkyo Univ., Stony Brook Univ.,

TITEC, Tokyo Met.College of Aero.Eng.,

1. Motivation in Spin Physics with Silicon Vertex Tracker (VTX)2. Advantage of VTX3. Simulation Results of ALL for Gamma-Jet with VTX4. VTX and Beam Test5. Summary

Motivation in Spin Program with VTX

• Requirements for detector

• Heavy flavor tagging and beauty and charm separation : Good vertex resolution

• x reconstruction with recoil jet (pT(), , jet) : Large solid angle coverage

• Gluon spin structure of the nucleon

• Gluon polarization G/G with charm, beauty.

• x dependence of G/G with -jet correlations.

VTX detector satisfied these requirements

Direct pT(),

Jet (jet)Large Acceptance

VTX Detector

• Four-Layer Barrel Detector• Pixel Sensor (Inner 2 Layers)　 (50 x 425 m2)

required for high occupancy• Strip Sensor （ Outer 2 Layers) (80 x 1000 m2)

Pixel Layersr=5.0cm z=±10cmr=2.5cm z=±10cm

Strip Layersr=10cm z=±16cmr=14cm z=±19cm

2 for || < 1.2

• Good DCA resolution DCA~ 50 m

• Large Acceptance|| < 1.2, 2 for

Simulation

charm and beauty separation with difference of their life time

Life time (c) D0 : 125 m B0 : 464 mDCA

DCA (m)

ppD

B

e

e

Backgroundc quarkb quark

pT (GeV/c)

Subtraction ofbackground

Advantage with VTX Detector (Heavy Flavor)

By simultaneous fittingthe DCA distribution

with the expected shapes,charm and beauty are separated.

Advantage with VTX Detector (-jet Measurement)

VTX can improve xgluon determination

PHENIX Direct || < 0.35

Jet|| < 0.35|jet| < 1.2

jet

vertex

|| < 0.35

|| < 1.2

Gamma - Jet with VTX

With jet axis reconstruction, improvement of the xg reconstruction.

Jet axis was reconstructed with VTX by using PYTHIA simulationxg is calculated by the kinematical reconstruction with jet axis information

Simple Cone Algorithm (corn radius < 0.5 in eta-phi space) was used.GeVs 500

ees

pxee

s

px jetjet TT

21 s

pxxx TT

221

Without VTX With VTX

w/o jet information w/ jet reconstruction

ALL distribution as function of xg

Gamma - Jet with VTX

GeVs 5001300 pbLIntegrated Luminosity

Center of mass energy

L = 300 pb -1

g = g

g = -g

GRSV_std

PYTHIA Simulation

P = 0.7

Sensor

R/O Chip

• Pixel R/O Chip• 425m(z) x 50m()/pixel• 32(z) x 256() = 8192 pixels• Active area is 12.8 x 13.6 mm2

• 150 m thickness• Operation at 10 MHz• Power consumption is 1W/chip

32 column25

6 ro

w

425mm

50m

m

Silicon Sensor

56.72mm

13.9

2mm

- Hybrid Pixel Sensor -• Technology developed by ALICE.• Bump-bonding between R/O chip and sensor..

• Pixel Sensor• Same pixel size of R/O chip• 200 m thickness

bump bond

R/O chip wafer

Sensor wafer

VTX Detector ( Pixel )

Sensor elements:

Finely segmented detector with 80 µm 1 mm, pixels. Each pixel region has two metal strips and collect charge from sensor.

- Strip Sensor -

• Single-sided sensor with 2-D position sensitivity

• Charge sharing by 2 spirals in one pixel

• Sensor (Hamamatsu) 3.5 x 6.4 cm2

625 m thickness

• Pixels : 384 x 30 x 2 = 23k

• Strips : 384 x 2 x 2 = 1.5k

128 ch/chip8 bit ADC

VTX Detector ( Strip )

VTX Detector

10

• Pixel detector = Inner 2 layers of VTX 1st layer : 10 pixel ladders = 40 hybrid sensor 2nd layer: 20 pixel ladders = 80 hybrid sensor

pixel ladders

• Strip detector = Outer 2 layers of VTX 3rd layer : 16 strip ladders = 80 strip modules 4th layer : 24 strip ladders = 144 strip modules

strip ladders5 or 6 strip module

cooling support

strip module

2 pixel bus

4 hybrid sensor

cooling support

VTX will be installed into PHENIX in 2010

FNAL Beam Test

To confirm functionality of silicon detector and DAQ system,full chain test had been performed by using beam at FNAL (MT984)

• 20-26 Aug MTest beam line• 120GeV/c proton beam• 10 x 10 mm2 beam-focus• 3 pixel detectors and 3 strip detectors

scintillatorS1 S2 S3 S4

Beam

PIXEL 3 LAYERS STRIP 3 LAYERS

RCC 3RCC 2RCC 1

FEM

SPIRO 3SPIRO 2SPIRO 1

FEM

PHENIXDAQ

DAQ

optical cable

We perform beam test at FNAL in order tocheck the functionality of silicon pixel ladder andconfirm DAQ system works properly

beam

PIXEL 3 LAYER

STRIP 3 LAYER

FNAL Beam Test

Layer 1

Layer 2

Layer 3

colrow

Intrinsic Resolutionfor row () direction

Beam

Event Display

row [m]

Preliminary

Clear tracking

chip1 chip2 chip3 chip4

FNAL Beam Test

Red circle : clusters with ADC > 3 sigma

Beam

Layer 3

Layer 5

Layer 6

Residual Distribution

RMS=0.91

RMS=0.45( =36 m )

RMS=0.90

Event Display

Summary

• Silicon Vertex Tracker (VTX) can enhance physics capability of the PHENIX detector.

• PYTHIA simulation was performed under the condition of and . Improvement for x reconstruction with gamma-jet production. Estimation of ALL as a function of xg.

• FNAL beam test was performed to confirm the functionality of detector and DAQ system. The system worked properly.

• Preparation for mass production is under way.

• VTX detector will be installed into PHENIX in 2010.

GeVs 5001300 pbL

Back Up

Advantage with VTX Detector

Baseline detectorVTX barrel upgrade

Gluon polarization will be measured byprompt photon (+ jet)single electron (charm and bottom tagging)

VTX extend the x-range.

DCA Resolution

pT (GeV/c)

DCA

DCA2

(12r2

2 22r1

2)

(r2 r1)2

ms2 r1

2

sin2

DCA resolution is dominated most inner two layers.

Occupancy (PISA Simulation)

Occupancy of the each layers in the central Au-Au collisions

• Pixel Layer

• N_hits : hit counts on each layer• N_allpix : all pixel numbers on each layer ( 32 x 256 x 4 x 4x 10(or20) )

• Strip Layer

• N_hits : hit counts on each layer• N_x(y)strip : all strip numbers on each layer ( 768 x 5(or6) x 16(or24) )

Method

• HIJING 3.17 Au-Au 200GeV/c• with impact parameter < 2fm• no magnetic field• initial vertex is (0, 0, 0)

allpixN

hitsNOccupancy

_

_

stripyxN

hitsNOccupancy

)(_

_

Occupancy (PISA Simulation)

Results

Layer1 Layer2

Layer3 Layer4

• number of track

9600/event

with silicon hit

• no charge sharing between strips

• no ghost track

Layer 1X/X0 ~ 2%

Layer 2X/X0 ~ 2%

Layer 3X/X0 ~ 3.5%

Layer 3X/X0 ~ 3.3%

CONDITION

• -1.2 < < 1.2 (FLAT)

• 0.0 < (degree) < 360 (FLAT)

Stave Thickness 300um Stave Width 31.3mm (ROC3 ½ oz)

Cone Algorithm

1. There are remaining charged particle after applying the cut of 1.0GeV/c < pT

2. Determination of first jet axis ( and ). Momentum weighted average in the opposite azimuthal direction of gamma.

3. Make a cone around a first jet axis. Here, apply cut of R < 0.5 and 1.0GeV/c < pT.

Calculate a momentum weighted average and determine second jet axis ( and ).

5. Calculate difference between ( and ) and ( and ).

6. Iterate from 3 to 5.

The iteration continue until jet direction no longer changes.

recoil parton

gamma

cone

gamma

22)( R

221

221 )( diff

jet i pT

i

i

pTi

i

jet i pT

i

i

pTi

i

ALL distribution as function of pT()

Gamma - Jet with VTX

GeVs 5001300 pbLIntegrated Luminosity

Center of mass energy

L = 300 pb -1

g = g

g = -g

GRSV_std

PYTHIA Simulation

P = 0.7

GeVs 200

5 x 102

2 x 101