m. oldenburg strange quark matter 2006 — march 26–31, los angeles, california 1 centrality...
TRANSCRIPT
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 1
Centrality Dependence ofAzimuthal Anisotropyof Strange Hadrons in
200 GeV Au+Au Collisions
Markus OldenburgEuropean Organisation for Nuclear Research CERN
for the STAR Collaboration
Strange Quark Matter 2006International Conference on Strangeness in Quark MatterMarch 26–31, University of California, Los Angeles, USA
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 2
Overview
• Motivation• Analysis details and technique
• Data and results for v2 and v4
• Discussion• Conclusions
PCM & clust. hadronization
NFD
NFD & hadronic TM
PCM & hadronic TM
CYM & LGT
string & hadronic TM
Time
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 3
x
zy
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
...])φ[2(2φcos211
2122
3
3
RRT
vvdydp
Nd
pd
NdE
])φ[2cos(2 Rv
Elliptic flow v2
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 4
Flow of strange hadrons
STAR:
• freeze-out of multi-strange hadrons- at higher temperature Tfo
- with lower collective velocity T
→ less interaction of strange hadrons with non-strange hadrons
• sensitivity to the early, partonic stageNucl. Phys. A715, 458c (2003)
Phys. Rev. Lett. 92, 112301 (2004)Phys. Rev. Lett. 92, 182301 (2004)
(GeV
)
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 5
Dataset and analysis method• system: Au+Au collisions
• energy: sNN = 200 GeV
• event sample: – 13.3 M events 0–80%– 6.6 M events 40–80%– 5.0 M events 10–40%– ~19 M events 0–10%
• event plane resolution:– 76% for 0–80%– 66% for 40–80%– 82% for 10–40%– 69% for 0–10%
• analysis method: v2 vs. minv
• motivated by Borghini et al. [nucl-th/0407041]
• detailed studies regarding systematic uncertainties still underway
• for K0S and Λ+Λ
– ~5% error on v2 for pT<4 GeV/c
– rising up to ~25–30% at 4<pT<6 GeV/c
– possible significant non-flow contribution for pT>5 GeV/c
• Only statistical errors shown in this presentation!
_
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 6
200 GeV Au+AuSTAR preliminary
• mass ordering at low pT
• ‘standard’ Hydro calculation: Tch=165 MeV, Tkin=130 MeV
[P. Huovinen, private communication]
• model works reasonably well for min. bias at low pT
Min. bias v2(pT) for strange hadronsK
0S and Λ data provided by Y
an Lu →
poste
ron
Thu
rsday
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 7
Centrality dependence of v2(pT)
• available high statistics allows for measurement of centrality dependence of v2(pT)
• comparison to Hydro model calculations shows deviations even at low pT
40-80%
10-40%
10-80%
0-10%0-10%
200 GeV Au+AuSTAR preliminary
K0S and Λ data provided by Yan Lu
→ poster on Thursday
[Hydro model results by P. Huovinen,
private communication]
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 8
NCQ scaling of v2(pT) for min. bias
PHENIX (open symbols): Phys. Rev. Lett. 91, 182301 (2003)
• scaled meson and baryon v2 agrees at intermediate pT
• high statistics measurements show deviation from ideal scaling
STAR preliminary200 GeV Au+Au
min. bias (0–80%)
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 9
Centrality dependence of NCQ scaling
• polynomial fit through K0S, Λ, and Ξ data
• NCQ scaling seems to work for different centralities as wellSee Yan Lu’s !poster on Thursday
200 GeV Au+Au
STAR preliminary
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 10
v4 for Ξ- and Ξ+_
• ideal fluid dynamics would lead to v4/v22 = 0.5
[Borghini and Ollitrault, nucl-th/0506045; Kolb, Phys. Rev. C 68, 031902(R)]• Incomplete thermalisation? [Borghini et al., Phys. Lett. B 627, 49 (2005)]
Will v4/v22 be closer to 0.5 at LHC?
Ξ+Ξ v4
_
1.2 v22
0.5 v22
200 GeV Au+Au
min. bias (0–80%)
STAR preliminary• Observation of sizable
v4 with strong pT dependence
• v4 scales with ~1.2 v22
(as it for charged hadrons) [STAR: Phys. Rev. C 72 014904 (2005)]
v4
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 11
Conclusions
• The strong flow of strange and multi-strange hadrons indicates collectivity among partons!
• strange hadron v2 at low pT:– show mass ordering– follow hydro model for minimum bias– deviate from hydro model predictions
for different centralities
• NCQ scaling of v2 at intermediate pT:– deviations from ideal NCQ scaling become
visible for minimum bias– indication for NCQ scaling even for different centralities
• v4 of Ξ-+Ξ+:– shows same scaling (1.2 v2
2) as other particle species– Hint for incomplete thermalisation?
_
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 12
Backup
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 13
Analysis technique
• analysis method: v2 vs. minv
• motivated by Borghini et al. [nucl-th/0407041]
• advantages over standard method:– only one fit per pT bin smaller systematic uncertainties
• method used for K0S, Λ, Ξ, ,
• standard method and v2 vs. minv method give consistent results and provide means for estimating systematic errors
)()()(
)(2cos()(
22
2
invinvBG
invSIG
invTOT
mBGSIG
BGmvm
BGSIG
SIGv
mv
SIG + BG
BG
BG(SIG+BG)
SIG (SIG+BG)
v2TOT(minv)
M. Oldenburg Strange Quark Matter 2006 — March 26–31, Los Angeles, California 14
Systematic error estimations for K0S and Λ
STAR preliminary STAR preliminary