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Spin Physics Capability with 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.,.

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slide1

Spin Physics Capability

with 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 VTX

3. Simulation Results of ALL for Gamma-Jet with VTX

4. VTX and Beam Test

5. Summary

slide2

Motivation in Spin Program with VTX

Direct g (pT(g), hg)

Large Acceptance

(hjet)

Jet

VTX detector satisfied these requirements

  • Gluon spin structure of the nucleon
    • Gluon polarization G/G with charm, beauty.
    • x dependence of G/G with -jet correlations.
  • Requirements for detector
    • Heavy flavor tagging and beauty and charm separation : Good vertex resolution
    • x reconstruction with recoil jet (pT(g), hg, hjet) : Large solid angle coverage
slide3

VTX Detector

  • Four-Layer Barrel Detector
    • Pixel Sensor (Inner 2 Layers)(50 x 425 mm2)
    • required for high occupancy
    • Strip Sensor(Outer 2 Layers) (80 x 1000 mm2)
  • Good DCA resolution
    • sDCA~ 50 mm
  • Large Acceptance
    • |h| < 1.2, 2p for f

|h| < 1.2

2p for f

Pixel Layers

r=5.0cm Dz=±10cm

r=2.5cm Dz=±10cm

Strip Layers

r=10cm Dz=±16cm

r=14cm Dz=±19cm

slide4

Advantage with VTX Detector (Heavy Flavor)

Simulation

Background

c quark

b quark

charm and beauty separation with difference of their life time

e

Life time (ct)

D0 : 125 mm

B0 : 464 mm

DCA

D

p

p

B

By simultaneous fitting

the DCA distribution

with the expected shapes,

charm and beauty are separated.

e

Subtraction of

background

DCA (mm)

pT (GeV/c)

slide5

Advantage with VTX Detector (g-jet Measurement)

|h| < 0.35

Direct g

PHENIX

|h| < 0.35

jet

Jet

|h| < 0.35

|h| < 1.2

vertex

|hjet| < 1.2

VTX can improve xgluon determination

slide6

Gamma - Jet with VTX

Jet axis was reconstructed with VTX by using PYTHIA simulation

xg is calculated by the kinematical reconstruction with jet axis information

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

Without VTX

With VTX

w/o jet information

w/ jet reconstruction

With jet axis reconstruction, improvement of the xg reconstruction.

slide7

Gamma - Jet with VTX

Center of mass energy

Integrated Luminosity

ALL distribution as function of xg

PYTHIA Simulation

Dg = g

GRSV_std

L = 300 pb -1

P = 0.7

Dg = -g

slide8

VTX Detector ( Pixel )

Silicon Sensor

56.72mm

13.92mm

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

bump bond

R/O Chip

Sensor

R/O chip wafer

  • Pixel R/O Chip
    • 425mm(z) x 50mm(f)/pixel
    • 32(z) x 256(f) = 8192 pixels
    • Active area is 12.8 x 13.6 mm2
    • 150 mm thickness
    • Operation at 10 MHz
    • Power consumption is 1W/chip

50mm

256 row

425mm

32 column

Sensor wafer

  • Pixel Sensor
    • Same pixel size of R/O chip
    • 200 mm thickness
slide9

VTX Detector ( Strip )

  • - 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 mm thickness

    • Pixels : 384 x 30 x 2 = 23k
    • Strips : 384 x 2 x 2 = 1.5k

Sensor elements:

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

128 ch/chip

8 bit ADC

slide10

VTX Detector

2 pixel bus

4 hybrid sensor

cooling support

pixel ladders

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

VTX will be installed into PHENIX in 2010

stripmodule

strip ladders

5 or 6 strip module

cooling support

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

10

slide11

FNAL Beam Test

STRIP 3 LAYERS

scintillator

S1

PIXEL 3 LAYERS

S4

S2

S3

Beam

SPIRO 1

SPIRO 2

SPIRO 3

RCC 1

RCC 2

RCC 3

optical cable

FEM

FEM

PHENIX

DAQ

DAQ

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
slide12

We perform beam test at FNAL in order to

check the functionality of silicon pixel ladder and

confirm DAQ system works properly

PIXEL 3 LAYER

STRIP 3 LAYER

beam

slide13

FNAL Beam Test

Layer 1

Layer 2

Layer 3

row

col

Event Display

Intrinsic Resolution

for row (f) direction

chip1 chip2 chip3 chip4

Beam

Preliminary

row [mm]

Clear tracking

slide14

FNAL Beam Test

Event Display

Residual Distribution

Beam

Layer 3

RMS=0.91

Layer 5

RMS=0.45

( =36 mm )

RMS=0.90

Layer 6

Red circle : clusters with ADC > 3 sigma

slide15

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.
slide17

Advantage with VTX Detector

Baseline detector

VTX barrel upgrade

Gluon polarization will be measured by

prompt photon (g + jet)

single electron (charm and bottom tagging)

VTX extend the x-range.

slide18

DCA Resolution

DCA resolution is dominated most inner two layers.

pT (GeV/c)

slide19

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)
slide20

Occupancy (PISA Simulation)

Results

  • number of track
  • 9600/event
  • with silicon hit
  • no charge sharing
  • between strips
  • no ghost track

Layer2

Layer1

Layer4

Layer3

slide21

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

Layer 2

X/X0 ~ 2%

Layer 1

X/X0 ~ 2%

Layer 3

X/X0 ~ 3.3%

Layer 3

X/X0 ~ 3.5%

  • CONDITION
  • -1.2 < h < 1.2 (FLAT)
  • 0.0 < f(degree) < 360 (FLAT)
slide22

Cone Algorithm

gamma

recoil parton

gamma

cone

1. There are remaining charged particle after

applying the cut of 1.0GeV/c < pT

2. Determination of first jet axis (h1 and f1).

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(h2 and f2).

5. Calculate difference between (h1 and f1) and (h2 and f2).

6. Iterate from 3 to 5.

The iteration continue until jet direction no longer changes.

slide23

Gamma - Jet with VTX

Center of mass energy

Integrated Luminosity

ALL distribution as function of pT(g)

PYTHIA Simulation

Dg = g

GRSV_std

L = 300 pb -1

Dg = -g

P = 0.7

slide25

5 x 102

2 x 101