# Presentation: 391226

- HeavyFlavor Collectivity –
- LightFlavor Thermalization at RHIC

- Kai Schweda, Berkeley Lab

- People:	S. Blyth, X. Dong, Y. Lu, M. Oldenburg, H.G. Ritter, A. Rose,	A. Shabetai, P. Sorensen, N. Xu, H. Zhang, Y. Zhang.

## Outline

- Motivation
- Heavy-Flavor Physics**** Heavy flavor (c,b) collectivity****Charm quark kinetic equilibration
- A Heavy-Flavor Tracker for STAR
- Summary

## Quark Gluon Plasma

- Source: Michael Turner, *National Geographic (1996)*

- _Quark Gluon Plasma:_
- Deconfined and
- thermalized state of quarks and gluons
- (?)  Can we create a QGP in a controlled mannerto establish its properties

## Time Scale

*Coalescence processes occur during (phase) transition and hadronization;*
*u-,d-quarks and ‘bound-states’ gain mass accompanied by expansion;*
*Early thermalization with partons and its duration need to be checked. *

*deconfinement*

*Phase and Chiral transitions*

*u-, d-quarks and ‘bound-states’ gain mass*

- Plot: N. Xu

## Anisotropy Parameter v2

- y

- x

- py

- px

- coordinate-space-anisotropy              momentum-space-anisotropy

**Initial/final conditions, EoS, degrees of freedom**

## Collectivity, Deconfinement at RHIC

-  -  v2, spectra of light hadrons
-     and multi-strange hadrons
-  -  scaling of the number of
-     constituent quarks
-  At RHIC, it seems we have:
****** ****Partonic Collectivity **
**Deconfinement***** ***
********* ******Thermalization ?***
*PHENIX**: PRL*_***91***_*, 182301(03)      *
*STAR**: PRL*_***92***_*, 052302(04)*
*S. Voloshin, NPA715, 379(03)*
*Models: Greco et al, PR*_***C68***_*, 034904(03)*
*X. Dong, et al., Phys. Lett. *_***B597***_*, 328(04).*
*...**.*

## Heavy-Flavor Quarks

- Plot: B. Mueller, nucl-th/0404015.

-  Charm(Beauty) quarks dominantly produced in initial collisions
-  Even in a QGP, charm and beauty quark-mass heavy !
-  Charm(Beauty) good probe for medium created at RHIC
-  If heavy quarks flow:  frequent interactions among all quarks light quarks (u,d,s) likely to be thermalized

- Plot: B. Mueller, nucl-th/0404015.

- Mass (MeV/c2)

- 106
- 105
- 104
- 103
- 102
- 10
-   1

## Charm Elliptic Flow

-  D  e +X
-  Sizeable elliptic flow
-  But: large background:***	*** 	 e+e-	0  e+e- large stat. and syst. uncertainties
-  *Need direct open charm reconstruction ! *

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

## Open Charm Flow

-  Two extreme scenarios:
- (a) No charm quark flow (PYTHIA)
- (b) Charm quark flow (Hydro)
-  Differences in D-meson spectra ~30% at pT < 2.0 GeV/c
- D  e + X: electron spectra undistinguishable !
-  Electron spectrum contains no information on dynamics
* **Need direct open charm reconstruction to low p**T**!*

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

## Open Charm Yields*

- No thermal creation of c or b quarks; m(c) = 1.1GeV >> T
- c and b quarks interact with lighter quarks  kinetic equilibration ? statistical recombination ?
- Ds+ / D0 ratio very sensitive !
- J/suppression vs recombination ?

|  | Pythia
p-p 200 GeV | Au-Au 
Statistical recombination* |
| --- | --- | --- |
| D+/D0 | 0.33 | 0.455 |
| Ds+/D0 | 0.20 | 0.393 |
| c+/D0 | 0.14 | 0.173 |
| J//D0 | 0.0003 | 0.0004
No suppression |

- *A. Andronic et al., *Phys. Lett. B571, 36 (2003).*

- D0  = cu
- Ds+ = cs** **

## D0 Reconstruction in STAR

- D0 Reconstruction in STAR

-  D0  + K, BR = 3.8%, *c* = 124m
-  calculate invariant mass in + K system
-  Peak around 1.86 GeV/*c*2
-  Large combinatorial background
-  Large stat. and syst. uncertainties
-  Need precise track information !
-  Need precise pointing device !

- Central Au + Au collisions in STAR

- TPC only

## The STAR Detector

## The Heavy Flavor Tracker

- Two layers
- 1.5 cm radius
- 5.0 cm radius
- 24 ladders
- 2 cm by 20 cm
- CMOS Sensors
- Precise (<10 m) , thin and low power
- 50 m thick chip + air cooling
- 0.36% radiation length
- Power budget 100 mW/cm2

## D0  + + K- Reconstruction

- Plot: A. Shabetai

- D0  + + K- Reconstruction

## Monte Carlo Simulations

- Plots: L. Pierpoint and A. Shabetai
- v2 calcs.: B. Zhang, L.-W. Chen and C.M. Ko, nucl-th/0502056

-  Au + Au, 50M central events
-  D0  K + 
-  Stat. uncertainties small
*** ******Probe charm quark flow !***
*** ******Probe light quark thermalization !***

## Summary

-  Measure spectra, elliptic flow and yields of **D****0**, D, **D****+****s**, C********* Probe (u,d,s)-quark thermalization*** *** ***
*** ******Need good momentum coverage to low p******T ******!***
********* ******A Heavy-Flavor Tracker (HFT) for STAR***