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Explore the QCD Phase Diagram - Partonic Equation of State at RHIC

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Explore the QCD Phase Diagram

- Partonic Equation of State at RHIC

Nu XuLawrence Berkeley National Laboratory

Many Thanks to the Organizers

- Introduction
2) STAR Experimental at RHIC

3) Partonic Collectivity in High-Energy Nuclear Collisions

- Identify and study the properties
- of the matter (EOS) with partonic
- degrees of freedom.

Hydrodynamic

Flow

Collectivity

Local

Thermalization

=

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

STAR Physics Focus

Polarized spin program

- Study proton intrinsic properties

Forward program

- Study low-xproperties, search for CGC

- Study elastic (inelastic) processes (pp2pp)

- Investigate gluonicexchanges

STAR Detector

EMC barrel

MRPC ToF barrel

Ready for run 10

EMC End Cap

RPSD

FMS

FPD

TPC

PMD

Complete

Ongoing

DAQ1000

Ready for run 9

FTPC

R&D

Full azimuthal particle identification!

e, π, ρ, K, K*, p, φ, Λ, Δ, Ξ, Ω, D, ΛC, J/ψ, Υ …

STAR Detectors: Full 2π particle identification!

EMC+EEMC+FMS

(-1 ≤ ≤ 4)

TPC

TOF

DAQ1000

HFT

FGT

TPC ToF TPC

STAR TPC

K pd

π

e, μ

STAR ToF

Log10(p)

STAR HFT

STAR EMC

Neutral particles Strange Jets Heavy Quark

hyperons Hadrons

Reconstruct particles in full azimuthal acceptance of STAR!

ud

ss

uud

sss

0-5%

more central collisions

Multi-strange hadron spectra are exponential in their shapes.

STAR white papers - Nucl. Phys. A757, 102(2005).

STAR: PRL. 99(2007)112301 Phys. Rev. Lett. 98, 62301(2007)

- mesons and Strange Baryons

ssbar fusion -meson formation!

STAR: Phys. Lett. B612, 81(2005)

The s-and d-quark Spectra

Assuming that the processes of hadronization follow coalescence

- parton spectra

- ‘partonic collective flow’

velocity ~ 0.35-0.45 c

JinHui Chen: SQM08

c.f. Phys. Rev. C78 (2008) 034907

STAR Detector

MTD

EMC barrel

MRPC ToF barrel

Ready for run 10

EMC End Cap

RPSD

FMS

FPD

TPC

PMD

Complete

Ongoing

DAQ1000

Ready for run 9

HFT

FGT

R&D

- Higgs mass: electro-weak symmetry breaking. (current quark mass)
- QCD mass: Chiral symmetry breaking. (constituent quark mass)
- New mass scale compared to the excitation of the system.
- Important tool for studying properties of the hot/dense medium at RHIC.
- Test pQCD predictions at RHIC.

Quark Masses

Total quark mass (MeV)

Charm Hadron v2

- 200 GeV Au+Aum.b.
- collisions (500M events).
- - Charm hadron collectivity
- drag/diffusion constants
- medium properties!

- 200 GeV Au+Aum.b.
- collisions (|y|<0.5 500M events)
- Charm hadron RAA
- energy loss mechanism, e.g.
- collisionalvs. radiative!

PRL (07)

- Di-leptons allow us to measure the direct radiation from the matter with partonic degrees of freedom, no hadronization!
- Low mass region:
- , , e-e+
- minve-e+
- medium effect
- Chiral symmetry
- - High mass region:
- J/e-e+
- minve-e+
- Direct radiation

Expanding partonic matter at RHIC and LHC!

Direct Radiation

- 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)

- Equation of State (EOS)
- No thermalization is needed – pressure gradient only depends on thedensity gradient and interactions.
Space-time-momentum correlations!

coordinate-space-anisotropy momentum-space-anisotropy

y

py

px

x

Initial/final conditions, EoS, degrees of freedom

1) Radial flow – integrated over whole history of the evolution

2) Directed flow (v1) – relatively early

3) Elliptic flow (v2) – relatively early

- Mass dependent: characteristic of hydrodynamic behavior.

P. Huovinen, private communications, 2004

- 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.

- v2 of light hadrons and

multi-strange hadrons

- scaling by the number

of quarks

At RHIC:

Nqscaling

novel hadronization

process

- Parton flow
- De-confinement
- PHENIX: PRL91, 182301(03)
- STAR: PRL92, 052302(04), 95, 122301(05)
- nucl-ex/0405022, QM05
- S. Voloshin, NPA715, 379(03)
- Models: Greco et al, PRC68, 034904(03)
- Chen, Ko, nucl-th/0602025
- Nonaka et al. PLB583, 73(04)
- X. Dong, et al., Phys. Lett. B597, 328(04).
- ….

i ii

“-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”

STAR: Phys. Rev. Lett. 99 (2007) 112301// * STAR, Duke, TAMU

** OZI rule

STAR: Phys. Rev. C77, 54901(2008)

200 GeV Au+Au

S. Voloshin, A. Poskanzer, PL B474, 27(00).

D. Teaney, et. al., nucl-th/0110037

- Larger v2/part indicates stronger flow in more central collisions.
- NO partscaling.
- The observed nq-scaling does not necessarily mean thermalization.

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

K0value 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 section

cs : speed of sound

S : transverse area

Ideal hydro v2/ε

- εfrom“optical”Glaubermodel

Simultaneous fits

Note: Fit v2{4} and v2{ZDC-SMD} for charged hadrons not plotted here

PHENIX π, K and p: preliminary, nucl-ex/0604011v1

STAR K0S, Λ, Ξ : 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

Drescher, Dumitru, Gombeaud, J.Ollitrault;

Phys. Rev. C76, 024905 (2007)

v2 max

- - Only approaching hydro limit at most central collisions!
- Questions:
- Viscous effects ?? or Non-thermalization in HI collisions ??

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

sQGPand the QCD Phase Diagram

- LGT prediction on the transition

temperature TC is robust.

- LGT calculation, universality, and

models hinted the existence of

the critical point on the QCD phase

diagram* at finite baryon chemical

potential.

- Experimental evidence for either

the critical point or 1st order

transition is important for our

knowledge of the QCD phase

diagram*.

* Thermalization has been assumed

M. Stephanov, K. Rajagopal, and E. Shuryak, PRL 81, 4816(98)

K. Rajagopal, PR D61, 105017 (00)

http://www.er.doe.gov/np/nsac/docs/Nuclear-Science.Low-Res.pdf

2010: RHIC Beam Energy Scan

2011: Heavy Quark measurements