# Presentation: 080196

## Direct Topological Identification of Charm in STAR

## The HI Physics at RHIC is Compelling ...

## “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 thermalization and 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**

## Single Electron Spectra

**Hydro and Pythia are extreme models on opposite ends of the spectrum **
**Single electron spectra are not sufficient to distinguish hard and soft physics below 3 GeV**
**We heard this message over and over again at QM2005**
**A nice boost to our program**
**We need direct topological identification of charm**

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

## Heavy Flavor Energy Loss

**Heavy Flavor energy loss is very topical**
**Gluon densities up to 3500 are insufficient to describe the data**
**Beauty dominates single electron spectra above 5 GeV**
**We need direct topological ID of Charm**

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

## Elliptic Flow with Charm

- M. Kaneta (PHENIX), J. Phys. G: Nucl. Part. Phys. 30, S1217 (2004).
- F. Laue et al. (STAR), nucl-ex/0411007, (2004).

## The HFT Allows us to do Topological ID of Open Charm

**The HFT Allows us to do Topological ID of Open Charm**

- Quarks. Gluons.  Neutrinos.  All those damn particles you can’t see.  That’s what drove me to drink.  But now I can see them !

## Our Uniqueness

**The HFT is unique at RHIC**
**It will be thin**
**50 ********m Silicon**
**0.36% radiation length**
**Our P****T**** threshold will be low, ~700 MeV**
**PHENIX will be ~ 2 GeV**
**This give us 5x the yield for charm and all of the global physics at low P****T**
**It will have high spatial resolution**
**c******** for the D****0**** is 124 ********m**
**Cut on DCA********K**** < 50 ********m**
**Requires ~10 ********m point resolution**
**It will track all charged particles **
**From the lowest momentum accepted by STAR to the highest **
**The HFT will cover the full azimuth of STAR (2********)**

- The only way PHENIX can beat us is by answering the physics questions by another route ... which can happen (e.g. dE/dx)

## The Heavy Flavor Tracker Mechanical Design

**Two Layers of Si**
**1.5 cm radius**
**4.5 cm radius**
**High Resolution**
**100,000,000 pixels**
**30 ********m x 30 ********m **
**10 ********m resolution**
**Thin – with low MCS**
**50 ********m thinned Si**
**0.36% radiation length**
**0.5 mm Beam Pipe**
**CMOS technology (Industry Standard)**
**24 Ladders**
**10 chips, 2 cm wide by 20 cm long**
**100 mW/cm****2**** power budget**
**air cooled**

## This is a killer program ...

**This is a killer program if we can do it for $5 million**

## In the succeeding talks ...

**There is a tool that makes this possible ...**
**We can add a vertex constraint to the tracking algorithms to replace the loss of the SVT information**
**This means we can accomplish our physics goals whenever we can define an accurate vertex**
**There are compromises**
**pp physics and peripheral physics will be degraded for lack of a precise vertex as will our spin goals**
**In this afternoon’s talks you will see that we can build a simplified HFT detector if the SVT is removed from STAR**
**The technology is achievable now**
**We will have a robust program of measurement with D****0****s and the measurement of charmed flow**
**The HFT will tag electrons for the vector meson program**
**It is a good program**

## The HFT in STAR

## Beam  pipe concept required for HFT

- (dimensions in mm)

## Beam  pipe concept required for HFT (central region)

- Beam pipe supports attach here

## Alignment and Spatial Calibration Procedure

**Map all detector surfaces for each 4 ladder arm assembly with the vision coordinate machine**
**Assemble the 6 arm assemblies and map their relative positions**
**Install in STAR preserving all relative positions**
**If outside tracker alignment is fully known use a few tracks to determine the 6 parameters defining position of HFT within the outer tracker**
**If the outside tracker is not spatially calibrated do it with tracking through the HFT**

- BarBar vertex detector in the vision coordinate measuring machine