1Jim Thomas - LBL

The STAR Heavy Flavor Tracker

in 10 slides or less

Jim ThomasLawrence Berkeley Laboratory

19 - January - 2007

2Jim Thomas - LBL

“Heavy Flavor” is the Final Frontier

• The QGP is the universally accepted hypothesis at RHIC

• The next step in confirming this hypothesis is the proof of thermalization of the light quarks in RHIC collisions

• The key element in proving this assertion is to observe the flow of charm … because charm and beauty are unique in their mass structure

• If heavy quarks flow– frequent interactions among all quarks

– light quarks (u,d,s) likely to be thermalized

Current quark: a bare quark whose mass is due to electroweak symmetry breaking

Constituent quark: a bare quark that has been dressed by fluctuations in the QCD sea

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How many c c-bar pairs per collision?

Theory: NN (c ) = 289 - 445 µb

Exp: NN (c ) = 900 - 1400 µb

20 - 30 c pairs per central Au+Au collision at √sNN = 200 GeV

Theory: NN (b) = 1.64 - 2.16 µb

Exp: NN (b) = ??

0.04 - 0.06 b pairs per central Au+Au collision at √sNN = 200 GeV

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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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R&D is Driven by the Fabrication Schedule

Driven by the availability of CMOS Active Pixel Sensors

Fab-1999 Fab-2001 Fab-2003 Fab-2004 Fab-2005 Fab-2006 Fab-2007 Fab-2009

Mimosa-1 Mimosa-4 Mimosa-8 MimoSTAR-1 MimoSTAR-2 MimoSTAR-3 MimoSTAR-4 UltraSTAR

Build a full detector with each

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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 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 – SSD – IST – HFT

– TPC pointing resolution at the SSD is ~ 1 mm

– SSD pointing at the IST is ~ 300 m

– IST pointing at the HFT is ~ 150 m

– HFT pointing at the VTX is better than 50 m

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The Heavy Flavor Tracker

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Keep the SSD, it is a beautiful detector!

• The SSD is thin– 1% - double sided Si

• The SSD lies at an ideal radius– 23 cm - midway between IP and IFC

• The SSD has excellent resolution – (rumor says better than design)

• The SSD is too large to be replaced– The money is better spent, elsewhere

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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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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 IST comes about 1 year later

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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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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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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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Selected Parameters and Specifications

Min I efficiency 98%

Accidental rate < 100 /cm2

Position resolution < 10 m

Number of pixels 135,168,000

Pixel dimension 30 m 30 m

Detector chip active area 19.2 mm 19.2 mm

Detector chip pixel array 640 640

Number of ladders 33

Ladder active area 192 mm 19.2 mm

Number of barrels 2

Inner barrel (9 ladders) r = 2.5 cm

Outer barrel (24 ladders) r = 7.0 cm