Heavy-Flavor Collectivity

1
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.
2
Outline

1. Motivation
2. Heavy-Flavor Physics- Heavy flavor (c,b)
   collectivity- Charm quark kinetic equilibration
3. A Heavy-Flavor Tracker for STAR
4. Summary

3
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

4
Time Scale
deconfinement
u-, d-quarks and bound-states gain mass
Phase and Chiral transitions
Plot N. Xu

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

5
Anisotropy Parameter v2
coordinate-space-anisotropy ?
momentum-space-anisotropy
y
py
x
px
Initial/final conditions, EoS, degrees of freedom
6
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 PRL91, 182301(03)
• STAR PRL92, 052302(04)
• S. Voloshin, NPA715, 379(03)
• Models Greco et al, PRC68, 034904(03)
• X. Dong, et al., Phys. Lett. B597, 328(04).

7
Heavy-Flavor Quarks

• 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

106 105 104 103 102 10 1
Mass (MeV/c2)
Plot B. Mueller, nucl-th/0404015.
Plot B. Mueller, nucl-th/0404015.
8
Charm Elliptic Flow

• D ? e X
• Sizeable elliptic flow
• But large background g ? ee- p0 ?
  ee-g ...? 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).
9
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 lt 2.0
  GeV/c
• D ? e X electron spectra undistinguishable !
• Electron spectrum contains no information on
  dynamics
• Need direct open charm reconstruction to low pT!

S. Batsouli et al., Phys. Lett. B 557 (2003) 26.
10
Open Charm Yields

• No thermal creation of c or b quarks m(c)
  1.1GeV gtgt T
• c and b quarks interact with lighter quarks ?
  kinetic equilibration ?? statistical
  recombination ?
• Ds / D0 ratio very sensitive !
• J/y suppression vs recombination ?

Pythia p-p 200 GeV Au-Au Statistical recombination
D/D0 0.33 0.455
Ds/D0 0.20 0.393
Lc/D0 0.14 0.173
J/y/D0 0.0003 0.0004 No suppression
D0 cu Ds cs
A. Andronic et al., Phys. Lett. B571, 36 (2003).
11
D0 Reconstruction in STAR

• D0 ? p K, BR 3.8, ct 124mm
• calculate invariant mass in p K system
• Peak around 1.86 GeV/c2
• Large combinatorial background
• ? Large stat. and syst. uncertainties
• Need precise track information !
• Need precise pointing device !

TPC only
Central Au Au collisions in STAR
12
The STAR Detector
13
The Heavy Flavor Tracker

• Two layers
• 1.5 cm radius
• 5.0 cm radius
• 24 ladders
• 2 cm by 20 cm
• CMOS Sensors
• Precise (lt10 mm) , thin and low power
• 50 mm thick chip air cooling
• 0.36 radiation length
• Power budget 100 mW/cm2

14
D0 ? p K- Reconstruction
Plot A. Shabetai
15
Monte Carlo Simulations

• Au Au, 50M central events
• D0 ? K p
• Stat. uncertainties small
• Probe charm quark flow !
• Probe light quark thermalization !

Plots L. Pierpoint and A. Shabetai v2 calcs. B.
Zhang, L.-W. Chen and C.M. Ko, nucl-th/0502056
16
Summary

• Measure spectra, elliptic flow and yields of
  D0, D?, Ds, LC? Probe (u,d,s)-quark
  thermalization
• Need good momentum coverage to low pT !
• ? A Heavy-Flavor Tracker (HFT) for STAR