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STAR Inner Tracking Upgrades

with an emphasis on the Heavy Flavor Tracker

presented by

Jim ThomasLawrence Berkeley Laboratory

11 / 08 / 2006

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The Light Quark Program at STAR is Compelling

Lattice results

Its hot

Its dense

and it flowsat the partonic scale

and , too!

Spectra

Vn

Jets & Rcp

Now we can make these measurements in the charm sector

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Heavy Flavor Energy Loss … RAA for Charm

• Heavy Flavor energy loss is uncertain

– Gluon densities up to 3500 are insufficient to describe the data

– ~ 1000 from light quark data

• Beauty dominates single electron spectra above 5 GeV and makes the model worse

M. Djordjevic, et. al. nucl-th/0507019

Current energy loss mechanisms can only account for part of the strong suppression of RAA for electrons

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Flow: Constituent Quark Number Scaling

In the recombination regime, meson and baryon v2 can be obtained from the quark v2 :

2 2 2 2v22

v3

v3v Btt

q tM q tp ppp

Does it work in the Charm Sector? A strong test of the theory

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Elliptic Flow with Charm

M. Kaneta (PHENIX), J. Phys. G: Nucl. Part. Phys. 30, S1217 (2004).

• D e +X

Single electron spectra from PHENIX show hints of elliptic flow

• The HFT will cut out large photonic backgrounds: e+e-

and reduce other large statistical and systematic uncertainties

• STAR can make this measurement with 50 M Au+Au events in the HFT

• Smoking gun for thermalization at RHIC!

Better if we can do direct topological identification of Charm

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Single Electron Spectra … are not sufficient

• Hydro and Pythia are extreme models on opposite ends of the model spectrum

– Charm in red, Beauty in Blue … Hydro is the solid line, Pythia is dashed

• Single electron spectra are not sufficient to distinguish hard and soft physics below 3 GeV

– We will also see this in the RAA measurements

• The decayed spectra are shown in black and are nearly indistinguishable

• We heard this message many times at QM05 and will hear it again at QM06

S. Batsouli et al., Phys. Lett. B 557 (2003) 26.

We need direct topological identification of Charm

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Direct Topological Identification of Open Charm

The STAR Inner Tracking Upgrades will identify the daughters in the decay and do a direct topological

reconstruction of the open charm hadrons.

No Mixed events, no random background subtraction.

Goal: Put a high precision detector near the IP to extend the TPC tracks to small radius

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• A new detector– 30 m silicon pixels

to yield 10 m space point resolution

• Direct Topological reconstruction of Charm

– Detect charm decays with small c, including D0 K

• New physics– Charm collectivity and

flow to test thermalization at RHIC

– Charm Energy Loss to test pQCD in a hot and dense medium at RHIC

• R&D with HFT + SSD

• A proposal has been submitted and a TDR is in preparation

The Heavy Flavor Tracker

The HFT: 2 layers of Si at mid rapidity

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Inner & Forward Tracking Upgrades

• The Inner Tracking Upgrade include

– HPD (1 layer)

– IST (2 layers)

• The ITUp will add high quality space points to tracks in the TPC

– Si at = 0

• The FTUp will add high quality space points at forward η

– 1 < η < 2

• High Rate tracking for heavy flavor physics and W production

3 or more layers of Si & GEMs at forward 2 or more layers of Si at = 0

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2 options for the location of Triple-GEM detectors (Barrel or Disk

configuration) B. Surrow et al., Nucl. Instr.

and Meth. B241 (2005) 293.

e+/e-

Forward Tracking Upgrade

• Polarized pp program at √s = 500 GeV at RHIC at BNL:

– Study the proton spin flavor structure of the proton spin

• W detection via W e decay– identification of the e charge

sign is critical

• Employ triple-GEM detectors as part of STAR tracking upgrade

– Low dead material, fast time response, precise hit determination, cost effective

– Barrel or Disk configuration

• With 4 conventional silicon disks in the forward direction

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Surround the Vertex with Si

The HFT is a thin detector using 50 m Si to finesse the limitations imposed by MCS

Add the HPD, IST, and SSD to form the STAR Inner Tracking Upgrade ( ITUp )

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~ 1 m

Inside the IFC– Goal: graded resolution from the outside – in

– TPC – IST – HPD – HFT

– TPC pointing resolution at the SSD is ~ 1 mm

– SSD pointing at the IST is ~ 300 m

– IST pointing at the HPD is ~ 150 m

– HPD pointing at the HFT is ~ 100 m

– HFT pointing at the VTX is ~ 50 m

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SSD

~ 60 cm

– Double sided Si wafers 300 m thick with 95 m x 4.2 cm strips

– Crossed at 35 mrad – effectively 30 m x 900 m

– One layer at 23 cm radius

– 20 ladders, 67 cm long

– air cooled

< 1.2

– 1 % radiation length @ = 0

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IST

~ 36 cm

– Singled sided Si wafers 300 m thick with 60 m x 4.0 cm strips

– Si pads ~ 1 mm**2 on the other side of each ladder

– Two layers at 17 & 12 cm radius

– 27 ladders, 52 cm long

– 19 ladders, 40 cm long

– air cooled

< 1.2

– 1.5 % per layer @ = 0

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HPD

~ 22 cm

– ALICE Hybrid Pixels 350 m thick, with 250 m in the sensor and 150 m in the ASIC

– 50 m x 425 m strips

– One layer at 9.1 cm radius

– 48 ladders, 28 cm long

– C6F14 Evaporative cooling

< 1.2

– 1.1 % radiation length @ = 0

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HFT

~ 17 cm

– Active Pixel Sensors, thinned to 50 m thickness

– 30 m x 30 m pixels

– Two layers at 7 & 2.5 cm radius

– 24 ladders, 19.2 cm long

– 9 ladders, 19.2 cm long

– air cooled

< 1.2

– 0.28 % radiation length @ = 0

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R&D in Run 7

A Three Layer Telescope with MimoSTAR II Chips.

A full system test from pixel to DAQ using an extension of one TPC sector trigger line.

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HFT R&D and Installation Timeline

Install MimoSTAR II

Telescope

06 07 08 09 10

X XX X X

Install MimoSTAR IV

Prototype Detector

Install MimoSTAR III

LadderInstall a

nd run

MimoSTAR IV

Detector (Full)

Install Ultra

STAR

Detector (Full)

Install and test Prototype detector.

Reduced diameter BP is required.

X marks the installation dates. Running comes after installation.

Proposed HFT Timeline – the HPD and IST come about 1 year later

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A Rich Physics Program

• There is a rich physics program when all of the STAR physics detectors are working together

– Flow in the Charm sector

– dE/dx in the Charm sector

– Recombination and RAA in the Charm sector

– Vector Mesons

– Charm Angular Correlations

– non-photonic electrons

– …

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Working with the rest of STAR … ( )n

Combining the power of the STAR TOF barrel to identify electrons with the ability of the TPC and Inner Tracking Upgrades to identify and eliminate conversion electrons means we can execute a vigorous single electron and di-electron program of measurements

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Summary

• The STAR Inner Tracking Upgrade will explore the Charm sector

• We will do direct-topological-reconstruction of open Charm

• Our measurements will be unique at RHIC

• The key measurements include– V2

– Energy Loss

– Charm Spectra, RAA & Rcp

– Vector mesons

– Angular Correlations

• The technology is available on an appropriate schedule

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Supplementary slides

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Si Pixel Developments in Strasbourg

• Mimosa – 1– 4k array of 20 m pixels

with thick epi layer

• Mimosa – 4– Introduce Forward

Biased Diode

• Mimosa – 5 – 1M array of pixels, 17

m pixels using AMS 0.6 process

– 4 msec readout scan rate

• Mimosa – 8– Fast parallel column

readout with internal data sparsification

– 200 sec readout scan rate

– MimoSTAR – 1 128x128 pixels using TSMC 0.25

– MimoSTAR – 2 128x128 pixels using AMS 0.35– Duct tape these to the STAR Beam Pipe for 07 run

– MimoSTAR – 3 320x640 pixels using AMS 0.35

– MimoSTAR – 4 640x640 pixels production run

– Ultra – 1

– Ultra – 2

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Addition Detail

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Copy the Alice HPD using only one layer

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HPD Ladders - Sector Layout

Image: INFN Padova HPD total ~ 1000 pixel chips, ≈ 107 pixels

Kapton cables MCM RDO section active area

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HPD Ladder Cross-Section

7-layerAluminumKapton Flex

200 m

150 m

1

2

3

4

5

6

READOUT CHIP

PIXEL DETECTOR

Aluminium

Polyimide

CARBON FIBER SUPPORT

1 ANALOG_GND 25µ2 ANALOG_ POWER 25µ3 HORIZONTAL LINES 10µ4 VERTICAL LINES 5µ5 DIGITAL_POWER 25µ6 DIGITAL_GND 25µ7 RES + CAPA PADS 15µ

1

2

5

6

Glue

COOLING TUBE

11mm

<350µm (design target)

235µm

?

PIXEL_BUS

7 77 7

SMD component

M. Morel