1. Multi-strange Hadron v2 and Partonic Collectivity
Markus Oldenburg
Lawrence Berkeley National Laboratory
STAR Heavy Flavor Workshop
October 13−15, 2005
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

2. STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL
Overview
Motivation on why to measure
v2 of multi-strange hadrons
Analysis details and technique
Data and results
Discussion
Conclusion
Outlook:
from multi-strange to heavy flavor
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

3. Timeline of a heavy-ion collision
hadronization
Ξ, , 
hadronic stage
, K, p
direct photons
initial collisions
hard scatterings,
jet production
partonic stage
thermal photons
Time
by S. Bass
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

4. Flow of strange hadrons
(GeV)
freeze-out of multi-strange hadrons
- at higher
temperature Tfo
- with lower
collective
velocity T
small cross section of strange hadrons with non-strange hadrons
sensitivity to the early, partonic stage
STAR:
Nucl. Phys. A715, 458c (2003)
Phys. Rev. Lett. 92, (2004)
Phys. Rev. Lett. 92, (2004)
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

5. STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL
Importance of  v2
STAR:
Phys. Rev. C65, (R) (‘02)
Phys. Lett. B612, 181 (2005)
Kaon coalescence effectively ruled out as a dominant channel for  production at these energies.
 is a true signal from the early stage of the collision!
anisotropic flow measurement of  will conclude:
type of the system at an early stage
partonic vs. hadronic
origin of observed scaling at intermediate pT
mass vs. particle type
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

6. STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL
Elliptic flow v2 x z y px py y x
non-central collisions: azimuthal anisotropy in coordinate-space
interactions  asymmetry in momentum-space
sensitive to early time in the system’s evolution
Measurement: Fourier expansion of the azimuthal pT distribution
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

7. STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL
Dataset
system: Au+Au collisions
energy: sNN = 200 GeV
event sample: ~11 M events
centrality: 0–80 %
event plane
resolution ~75 %
correction:
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

8. Particle identification and mass spectra
identified via decay topology:
 K+ + K-
background estimation by event mixing
> 10,000,000 particles identified
Ξ- and (anti- Ξ)+
identified via decay topology:
Ξ  Λ +  and Λ  p + 
background estimated by
rotating the Λ by 180°
in the transverse plane
> 450,000 particles identified
Ω- and (anti-Ω)+
identified via decay topology:
  Λ + K and   p + 
background estimated by
rotating the Λ by 180°
in the transverse plane
> 13,000 particles identified
 results by Sarah Blyth
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

9. New analysis technique
analysis method: v2 vs. minv
motivated by
Borghini et al. [nucl-th/ ]
advantages over standard method:
only one fit per pT bin
smaller systematic uncertainties
new method used for K0S, Λ, Ξ, , and  analysis
standard method and v2 vs. minv method give consistent results
SIG + BG BG BG
(SIG+BG)
SIG
(SIG+BG)
v2TOT(minv)
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

10. v2 of multi-strange hadrons_
common fit to K and Λ
n = number of constituent quarks
[X. Dong et al.,
Phys. Lett. B597 (2004)] v2
Ξ+Ξ
Ω+Ω  _
baryons
mesons
pT/n > 0.75 GeV/c
2/ndf for NCQ=2
2/ndf for NCQ=3
Ξ+Ξ
82.7/6
27.4/6
Ω+Ω
4.1/3
2.1/3 
2.0/5
7.4/5 _
200 GeV
Au+Au _
 results by Sarah Blyth
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

11. Discussion of strange hadron v2 results
K0S and Λ results by Yan Lu
STAR preliminary
 results by Sarah Blyth
Hydro:
P. Huovinen,
priv. comm. (2004)
The strange baryons Ξ and Ω show strong elliptic flow.
The Ξ v2 clearly follows the baryon v2(pT).
 flows as strongly as other mesons.
Collective flow is generated during the partonic stage already.
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

12. Conclusions from the measurements
v2 of multi-strange hadrons:
, Ξ, and  show strong elliptic flow.
Their behavior is similar to the other mesons and baryons.
They flow as strongly as the other particles.
NCQ scaling of v2 :
observed scaling is a meson↔baryon, not a mass effect!
Collectivity develops early among partons! =
Partonic Collectivity at RHIC
Thermalization?
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

13. Timeline of a heavy-ion collision
production of heavy quarks
hadronization
Ξ, , 
hadronic stage
, K, p
direct photons
initial collisions
hard scatterings,
jet production
partonic stage
thermal photons
Time
by S. Bass
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL

14. STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL
Heavy-Flavor Quarks
B. Mueller, nucl-th/
Mass (MeV/c2)
106
105
104
103
102 10 1
Even in a QGP with chiral restoration, the c, b (and t) quarks stay heavy.
If charm quarks show collective behavior (= flow) the must have suffered frequent interactions with the light quarks u, d, s.
The light quarks u, d, s must be thermalized.
M. Oldenburg
STAR Heavy Flavor Workshop — October 13–15, 2005, LBNL