Nu Xu 1/28 VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November, 2008 Explore the QCD Phase Diagram - Partonic Equation of State at RHIC Nu Xu Lawrence Berkeley National Laboratory Many Thanks to the Organizers
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Explore the QCD Phase Diagram - Partonic Equation of State at RHIC
Explore the QCD Phase Diagram - Partonic Equation of State at RHIC Nu Xu Lawrence Berkeley National Laboratory Many Thanks to the Organizers. Outline. Introduction 2) STAR Experimental at RHIC 3) Partonic Collectivity in High-Energy Nuclear Collisions. Physics Goals at RHIC. - PowerPoint PPT Presentation
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Nu Xu 1/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Explore the QCD Phase Diagram
- Partonic Equation of State at RHIC
Nu XuLawrence Berkeley National Laboratory
Many Thanks to the Organizers
Nu Xu 2/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Outline
1) Introduction
2) STAR Experimental at RHIC
3) Partonic Collectivity in High-Energy Nuclear Collisions
Nu Xu 3/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
- Identify and study the properties of the matter (EOS) with partonic degrees of freedom.
- Explore the QCD phase diagram.
Physics Goals at RHIC
HydrodynamicFlow Collectivity Local
Thermalization=
Nu Xu 4/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
STAR Experiment
Nu Xu 5/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
STAR Physics Focus
1) Heavy-ion program - Study medium properties, EoS - pQCD in hot and dense medium
2) RHIC beam energy scan - Search for critical point - Chiral symmetry restoration
Polarized spin program - Study proton intrinsic properties
Forward program - Study low-x properties, search for CGC - Study elastic (inelastic) processes (pp2pp) - Investigate gluonic exchanges
Nu Xu 6/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
energy loss mechanism, e.g. collisional vs. radiative!
Nu Xu 16/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Direct Radiation
Expanding partonic matter at RHIC and LHC!Di-leptons allow us to measure the direct radiation from the matter with partonic degrees of freedom, no hadronization!
- Low mass region: , , e-e+
minv e-e+
medium effect Chiral symmetry
- High mass region: J/ e-e+
minv e-e+
Direct radiation
PRL (07)
Nu Xu 17/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Pressure, Flow, …
tds = dU + pdV s– entropy; p – pressure; U – internal energy; V – volume
t = kBT, thermal energy per dof
In high-energy nuclear collisions, interaction among constituents and density distribution will lead to:
pressure gradient collective flow
number of degrees of freedom (dof)Û Equation of State (EOS)Û No thermalization is needed – pressure gradient only
depends on the density gradient and interactions. Space-time-momentum correlations!
Nu Xu 18/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Nu Xu 19/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Transverse Flow Observables
1) Radial flow – integrated over whole history of the evolution 2) Directed flow (v1) – relatively early3) Elliptic flow (v2) – relatively early
- Mass dependent: characteristic of hydrodynamic behavior.
€
dr σ
dΩ=
d3σ
dpxdpydpz
=dN
p tdp tdydϕ=
1
2π
dN
p tdp tdy1+ 2v icos(i ϕ )
i=1
∑ ⎡
⎣ ⎢
⎤
⎦ ⎥
p t = p x2 + p y
2 , m t = p t2 + m2
v i = cos(iϕ )event
ϕ = tan−1 py
px
⎛
⎝ ⎜
⎞
⎠ ⎟
Nu Xu 20/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
v2 at Low pT Region
- Minimum bias data! - At low pT, model result fits mass hierarchy well - Collective motion at RHIC- More work needed to fix the details in the model calculations.
P. Huo
vi ne
n, p
r ivate
com
mu
nica
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04
Nu Xu 21/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Collectivity, Deconfinement at RHIC - v2 of light hadrons and multi-strange hadrons - scaling by the number of quarks
At RHIC: Nq scaling novel hadronization processê Parton flow De-confinement
S. Voloshin, NPA715, 379(03)Models: Greco et al, PRC68, 034904(03)Chen, Ko, nucl-th/0602025Nonaka et al. PLB583, 73(04)X. Dong, et al., Phys. Lett. B597, 328(04).….
i ii
Nu Xu 22/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
-meson Flow: Partonic Flow
“-mesons are produced via coalescence of seemingly thermalized quarks in central Au+Au collisions. This observation implies hot and dense matter with partonic collectivity has been formed at RHIC”
Larger v2/part indicates stronger flow in more central collisions. NO part scaling. The observed nq-scaling does not necessarily mean thermalization.
S. Voloshin, A. Poskanzer, PL B474, 27(00).D. Teaney, et. al., nucl-th/0110037
Nu Xu 24/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Knudsen Fit
– Assuming that σ is same for all hadrons Note: only extract the product K0σcs
K0 = 0.7 and cs2 = 1/3 (fixed)
– S is estimated from Glauber MC simulation– K0 value is determined so as to reproduce the
transport model calculation (K0 = 0.7 ± 0.03)* *C. Gombeaud and J.-Y. Ollitrault, PRC77, 054904 (2008)
σ : partonic cross sectioncs : speed of soundS : transverse area
Nu Xu 25/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Centrality Dependence of v2
• Ideal hydro v2/ε - ε from “optical” Glauber
model
• Simultaneous fits
Note: Fit v2{4} and v2{ZDC-SMD} for charged hadrons not plotted here
PHENIX π, K and p: preliminary, nucl-ex/0604011v1STAR K0
S, Λ, : Phys. Rev. C77, 054901 (2008)STAR φ : Phys. Rev. Lett. 99, 112301 (2007)Ideal Hydro. : P. Huovinen and P. V. Ruuskanen, Annu. Rev. Nucl. Part. Sci. 56, 163 (2006) and private communication
Nu Xu 26/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
Ideal Hydrodynamic Limit
- Only approaching hydro limit at most central collisions!- Questions:
Viscous effects ?? or Non-thermalization in HI collisions ??
Nu Xu 27/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
sQGP and the QCD Phase Diagram
In 200 GeV Au+Au collisions at RHIC, strongly interacting matter formed:
- Jet energy loss: RAA
- Strong collectivity: v0, v1, v2
- Hadronization via coalescence: nq-scaling
Questions:Has the thermalization reached at RHIC?- Serious analysis with dN/dpT and dv2/dpT results…
- Heavy quark measurements
When (at which energy) does this transition happen?What does the QCD phase diagram look like?- RHIC Beam Energy Scan
Nu Xu 28/28VIII International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro, Brazil, 3-6, November , 2008
The QCD Critical Point- LGT prediction on the transitiontemperature TC is robust.
- LGT calculation, universality, andmodels hinted the existence ofthe critical point on the QCD phasediagram* at finite baryon chemicalpotential. - Experimental evidence for eitherthe critical point or 1st order transition is important for ourknowledge of the QCD phase diagram*.
* Thermalization has been assumed
M. Stephanov, K. Rajagopal, and E. Shuryak, PRL 81, 4816(98)