CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 1 Nu Xu Lawrence Berkeley National Laboratory Part I: QM04 Highlights (experiment) Part

CCAST, Beijing, China, 2004Nu XuNu Xu 11

//Nxu/tex3/TALK/2004/08CCAST

Nu Xu

Lawrence Berkeley National Laboratory

Part I:

QM04 Highlights (experiment)

Part II:

Transverse Dynamics at RHIC



QM04 HighlightsQM04 Highlights

Part IPart I



Quark Matter ConferenceQuark Matter Conference

http://qm2004.lbl.gov/



Blue Ring (clockwise) Yellow Ring Yellow Ring

ARC

Four Experiments:BRAHMSPHENIXPHOBOS STAR

~ 1200 physicists: high energy/nuclear

Started in the Summer of 2000~ 200 publications (summer ‘04)



RHIC @ Brookhaven National LaboratoryRHIC @ Brookhaven National Laboratory

h

STAR

PHENIX

PHOBOS

BRAHMS



Colliding SystemsColliding Systems

Run-I 19.6 GeV Au+Au 2000130 GeV Au+Au 2000

Run-II 200 GeV Au+Au 2001200 GeV p+p 2001

Run-III 200 GeV d+Au 2002

Run-IV 200 GeV Au+Au 2004



People at RHICPeople at RHIC

More than 1000 people from around the worldBrazil, Canada, China, Croatia, Denmark, France,

Germany, India, Israel, Japan, Korea, Norway, Poland,

Russia, Sweden, UK, USA



Identify and study the properties of matter with partonic degrees of freedom.

Penetrating probes Bulk probes - direct photons, leptons - spectra, v1, v2 …

- “jets” and heavy flavor - partonic collectivity - fluctuations

jets - observed high pT hadrons (at RHIC, pT(min) > 3 GeV/c) collectivity - collective motion of observed hadrons, not necessarily reached

thermalization among them.

Physics Goals at RHIC

HydrodynamicFlow

CollectivityLocal

Thermalization=


//Nxu/tex3/TALK/2004/08CCAST PPhase diagram of strongly hase diagram of strongly

interacting matterinteracting matter

CERN-SPS, RHIC, LHC: high temperature, low baryon density

AGS, GSI (SIS200): moderate temperature, high baryon density



QCD on LatticeQCD on Lattice

Lattice calculations predict TC ~ 170 MeV

1) Large increase in a fast cross cover !

2) Does not reach ideal, non-interaction S. Boltzmann limit ! many body interactions Collective modes Quasi-particles are necessary

3) TC ~ 170 MeV robust!

Z. Fodor et al, JHEP 0203:014(02) Z. Fodor et al, hep-lat/0204001C.R. Allton et al, hep-lat/0204010F. Karsch, Nucl. Phys. A698, 199c(02).



Study of Nuclear Collisions Like…Study of Nuclear Collisions Like…P.C. Sereno et al. Science, Nov. 13, 1298(1998). (Spinosaurid)

Bulk Bulk PropertiesProperties

High pHigh pTT - -

QCD probesQCD probes



Au + Au Collisions at RHICAu + Au Collisions at RHIC

STARSTAR

Central Event

(real-time Level 3)



Collision Geometry, FlowCollision Geometry, Flow

x

z

Non-central Collisions

Number of participants: number of incoming nucleons in the overlap regionNumber of binary collisions: number of inelastic nucleon-nucleon collisions

Charged particle multiplicity collision centralityReaction plane: x-z plane

Au + Au sNN = 200 GeV



Global: Charge hadron densityGlobal: Charge hadron density19.6 GeV 130 GeV 200 GeV

Charged hadron pseudo-rapidity

1) High number of Nch indicates initial high density;2) Mid-y, Nch Npart nuclear collisions are not incoherent;3) Saturation model works

Important for high density and thermalization.

PRL 85, 3100 (00); 91, 052303 (03); 88, 22302

(02), 91, 052303 (03)

PHOBOSCollaboration



Particle production at RHICParticle production at RHIC

Bulk productionCollective effectsNew form of matter

pQCD

Soft (hydro)

0 1 2 3 4 5 6 7 8 9 10 11 12 GeV/c

Large Q2 resultsMedium modification of hard probes - partonenergy loss

Unclear regionNew observations



High/Intermediate pHigh/Intermediate pTT

1) Expect QCD calculations can be used as guidance

2) New tool at high energy nuclear collisions



Energy Loss in A+A Collisions

σddpd

ddpNd

TpR

TNN

TAA

AATAA /

/1)(

2

2

=

Nuclear Modification Factor:

back-to-back jets disappear

leading particle suppressed

p+p Au + Au



Jet QuenchingJet Quenching

Hadron suppression at intermediate pT, caused by energy loss of energetic objects, - ‘Jet quenching’!



Jets Observation at RHIC

p+p collisions at RHICJet like events observed

Au+Au collisions at RHICJets?



Suppression and correlationSuppression and correlation

Hadron suppression and disappearance of back-to-back ‘jet’ are correlated!



Di-jet tomography: PredictionsDi-jet tomography: Predictions

In-plane

Out-of-plane

X.N. Wang

dE/dx path length L!



Di-hardron tomographyDi-hardron tomography

pTtrig=4.0-6.0 GeV/c, ||<1.0, 2.0<pT

assoc<pTtrig

- Back-to-back suppression depends on the reaction plane orientation: i.e. energy loss dependence on the path length

-Powerful tool to study hadronization process in heavy ion collisions

A. TangQM04

STAR Preliminary

20-60%20-60%20-60%

STAR preliminary



Energy loss and equilibriumEnergy loss and equilibrium

Leading hadrons

Medium

In Au +Au collision at RHIC: - Suppression at the intermediate pT region - energy loss cause by the final state interactions- The energy loss leads to progressive equilibrium in Au+Au collisions STAR: nucl-ex/0404010



Direct Direct : a colorless probe: a colorless probe

1 + ( pQCD direct x Ncoll) / ( phenix pp backgrd x Ncoll)

PHENIX Preliminary (PbGl / PbSc Combined)

1 + ( pQCD direct x Ncoll) / phenix backgrd Vogelsang NLO

PHENIX: Direct photons are described by a curve that includes the measured suppressed 0 production in Au+Au collisions. (Au+Au at 200 GeV: 0-10%)

Transverse momentum pT (GeV/c)



RRAAAA for for 00 in Central Collisions in Central Collisions

D. d’Enterria QM04nucl-ex/0403055

SPS Energies: A.L.S.Angelis, PL B185, 213 (87)

WA98, EPJ C23, 225 (2002)

RHIC Energies:

PHENIX, PRL 88 022301 (02)PRL 91, 072303 (03)

p+p collision results changed

Finite energy loss in central heavy ion collisions at SPS energies!



Summary: High/Intermediate pSummary: High/Intermediate pTT

1) From run I - III, particle spectra were measured up to pT~10-12 GeV/c;

2) Energy loss effect observed at intermediate region in central Au+Au collisions at 200GeV;

3) Back-to-back ‘jets’ disappears;4) The energy loss depends on the path length - new!

Future:

• Cronin effect - energy, hadron type dependence• Hadronization process in p+p and Au+Au collisions• Origin of v2 at intermediate pT region (2-6 GeV/c)• …



Open Charm ProductionOpen Charm Production

1) Production through gluon fusing - sensitive to the initial condition for heavy ion collisions

2) Interacting with medium - sensitive to medium properties

3) Heavy intrinsic mass - a test the predictive power of QCD calculation



QCD Energy ScaleQCD Energy Scale

s-quark mass ~ 0.2 GeV, similar to values of TC critical temperature QCD QCD scale parameter TCH chemical freeze-out temperature

= 4f chiral breaking scale

mC

c-quark mass ~ 1.2 - 1.5 GeV >> QCD -- pQCD production - parton density at small-x -- QCD interaction - medium properties

Rcc ~ 1/mC => color screening J/ => deconfinement and thermalization

u-, d-, s-quarks: light-flavors || c-, b-quarks: heavy-flavorsheavy-flavors

1/x



Electron spectraElectron spectra

An increasing excess found at higher pT region, pT > 1.0 GeV/c, Expected contribution of semi-leptonic decays from heavy flavor hadrons

STAR Preliminary



Consistent in D measurementsConsistent in D measurements

Directly reconstructed D mesons

D and electron spectra are consistent!

STAR: nucl-ex/0404029 STAR Preliminary

Electrons from D decay



Open Charm spectra

An increasing excess found at higher pT region, pT > 1.0 GeV/c, Expected contribution of semi-leptonic decays from heavy flavor hadrons pQCD distributions are steeper and total cross sections are lower CGC: D. Kharzeev and K. Tuchin, NPA735, 248(04).

STAR: nucl-ex/0406



Charm production cross-sectionCharm production cross-section

1) NLO pQCD calculations under-predict the ccbar production cross section at RHIC

2) Power law for ccbar production cross section from SPS to RHIC: n ~ 2

(n~0.5 for charged hadrons)

3) Large uncertainties in total cross section due to rapidity width, model dependent(?).

STAR Preliminary



Some SPS resultsSome SPS results



NA49 ExperimentNA49 Experimenthttp://na49info.cern.ch/

Pb+Pb collision at 158A GeVPb+Pb collision at 158A GeV



Rapidity spectraRapidity spectra

(open dots from reflection at ycm= 0)

Extrapolation 4π yields

also: ,



Statistical model at at 40A, 80A GeV Statistical model at at 40A, 80A GeV

At lower energies B increases, while T decreases slightly



Particle yields – statistical modelParticle yields – statistical model

• hadron species populated according to phase space probabilities (max.entropy) (Fermi,Hagedorn)

• strangeness sector not fully saturated (Rafelski)

• statistical model successful, T, B, S, V

• larger value of S in A+A due to relaxation of local strangeness conservation

(fits by F.Becattini et al, PRC69(2004)024905)



Ratio of strange hadrons to pionsRatio of strange hadrons to pions

hadronic

mixed

partonic

Strangeness to pion ratio peaks sharply at the SPS

deconfinement?

€

ES ≈ NS +N

S

N ,u d

≈0.21

hadr

onic

mixed

partonic

€

F =s − 2∗mN( )

3 / 4

s( )1/ 4 ≈ s( )

1/ 2



Mid-rapidity transverse mass spectraMid-rapidity transverse mass spectra 158A GeV

well described by fireball model assuming common temperature and flow

“blast wave”:

(Schnedermann,Sollfrank, Heinz : PRC 48 (1993) 2462)



Part I: summaryPart I: summary

Topics are not covered:

• Color Glass Condensation: small-x cold QCD physics• Peripheral collisions at RHIC• HBT issues at RHIC• Astrophysics and heavy ion collisions• New theoretical development



Transverse Dynamics at RHICTransverse Dynamics at RHIC

Part IIPart II



Pressure, Flow, …Pressure, Flow, …

ddσσ = dU + pdV = dU + pdV σ– entropy; p – pressure; U – energy; V – volume

= kBT, thermal energy per dof

In high-energy nuclear collisions, interaction among constituents and density distribution will lead to: pressure gradient pressure gradient collective flow collective flow

number of degrees of freedom (dof) Equation of State (EOS) No thermalization is needed – pressure gradient only depends on the density gradient and interactions. Space-time-momentum correlations!



Transverse flow observablesTransverse flow observables

As a function of particle mass:• Directed flow (v1) – early• Elliptic flow (v2) – early• Radial flow – integrated over whole evolution

Note on collectivity:1) Effect of collectivity is accumulative –

final effect is the sum of all processes. 2) Thermalization is not needed to develop collectivity -

pressure gradient depends on density gradient and interactions.

€

dNptdptdydϕ

= 12

dNptdptdy

1+ 2vi (cos iϕ )i=1

∑ ⎡

⎣ ⎢

⎤

⎦ ⎥

pt = px2 +py

2 , mt = pt2 +m2



Hadron spectra from RHICHadron spectra from RHICp+p and Au+Au collisions at 200 GeVp+p and Au+Au collisions at 200 GeV



Hadron production & chemical freeze-outHadron production & chemical freeze-out

1) Chemical fit well to all hadron ratios at RHIC: Tch = 160 ± 10 MeV B = 25 ± 5 MeV S = 1 ± 0.05

Necessary for QGP!

2) The temperature parameter Tch is close to the critical temperature TC predicted by LGT calculations chemical equilibrium at the phase boundary

3) Since 1999, many work in this direction

Review:P. Braun-Munzinger et al. nucl-th/0304013



Compare with hydrodynamic model

This model results fit to pion, Kaon, and proton spectra well, but over predicted the values of <pT> for multi-strange hadrons



Hydro model: for , , p spectra



Thermal model fitThermal model fit

Source is assumed to be:– Local thermal equilibrated– Boosted radically

random

boostedE.Schnedermann, J.Sollfrank, and U.Heinz, Phys. Rev. C48, 2462(1993)

€

Ed3N

dp3∝ e−(uμ pμ )/T fo p

σ

∫ dσ μ ⇒

dN

mTdmT

∝ rdrmTK1

mT coshρ

Tfo

⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟0

R

∫ I0

pT sinhρ

Tfo

⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟

ρ = tanh−1β r β r = β S

r

R

⎛

⎝ ⎜

⎞

⎠ ⎟α

α = 0.5,1,2



Early freeze-outCentral Au+Au collisions at RHIC

1) Multi-strange hadrons seem to freeze out earlier than others sensitive probe for early dynamics

2) Charm-hadrons should be better. A possible complication is the pQCD hard spectrum.

3) J/ coalescence/melting: a tool for early dynamics CGC, deconfinement, and thermal equilibrium

PHENIX: Phys. Rev. C69 034909 (04).STAR: Phys. Rev. Lett. 92, 112301(04);

Phys. Rev. Lett. 92, 182301(04). A. Andronic et al., NPA715, 529(03). P. Kolb et al., Phys. Rev. C67 044903(03)

Chemical Freeze-out: inelastic interactions stopKinetic Freeze-out: elastic interactions stop



Blast wave fits: Tfo vs. < >

1) 1) , , KK, and , and pp change change smoothly from peripheral smoothly from peripheral to central collisions.to central collisions.

2) At the most central2) At the most central collisions, <collisions, <TT> reaches> reaches

0.6c.0.6c.

3) Multi-strange particles 3) Multi-strange particles ϕϕ,, are found at higher Tare found at higher T and lower <and lower <TT>>

Sensitive to early Sensitive to early partonic stage!partonic stage!

How about vHow about v22??

STAR: NPA715, 458c(03); PRL 92, 112301(04); 92, 182301(04).

200GeV Au + Au collisions200GeV Au + Au collisions



Equation of State

€

∂Tμν = 0

∂μ jμ = 0 j μ (x) = n(x)uμ (x)

T μν = ε(x) + p(x)[ ]uμuν − gμν ∗p(x)

Equation of state:

- EOS I : relativistic ideal gas: p = /3- EOS H: resonance gas: p ~ /6- EOS Q: Maxwell construction:

Tcrit= 165 MeV, B1/4 = 0.23 GeV

lat=1.15 GeV/fm3

P. Kolb et al., Phys. Rev. C62, 054909 (2000).

With given degrees of freedom, the EOS - the system response to the changes of the thermal condition - is fixed by its p and T().

Energy density GeV/fm3



y

x

py

px

coordinate-space-anisotropy momentum-space-anisotropy

Anisotropy parameter vAnisotropy parameter v22

€

=⟨y 2 − x 2⟩⟨y 2 + x 2⟩

v2 = cos2ϕ , ϕ = tan−1(py

px

)

Initial/final conditions, EoS, degrees of freedom



v2 at Low pT

- At low pT, hydrodynamic model fits well for minimum bias events indicating early thermalization in Au+Au collisions at RHIC!- More theory work needed to understand details: such as centrality dependence of v2; consistency between spectra and v2 …

P. H

uo

vi ne

n, p

r ivate

com

mu

nica

t i on

s, 20

04



Partonic collectivity at RHIC

v2, the spectra of multi-strange hadrons, and thescaling of the number ofconstituent quarks

Partonic collectivity has been attained at RHIC! Deconfinement, model dependently, has been attained at RHIC!

Next question is thethermalization of lightflavors at RHIC:- v2 of charm hadrons- J/ yield, distributions

PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04)



Nuclear modification factorNuclear modification factor

)/(

)/()(

2

2

dydpNNd

dydpNNdpR

Tperipheralbinary

peripheral

Tcentralbinary

central

TCP = 1) Baryon vs. meson effect!

2) Hadronization via coalescence

3) Deconfinement at RHIC - (K0, ): PRL92, 052303(04); NPA715, 466c(03); - R. Fries et al, PRC68, 044902(03)



Freeze-out systematicsFreeze-out systematics

The additional increase in T is likely due to partonic pressureat RHIC.

1) Smaller baryon chemical potential B = 25 MeV with Tch = 160 MeV2) Stronger transverse flow, T= 0.6(c)



STAR 200 GeV vSTAR 200 GeV v22

Anti-proton fit well by the hydrodynamic model with initial velocity kick ( = 0.02fm-1), but pions fail!

Much more theory work ahead

P. Kolb and R. Rapp, Phy. Rev. C67, 044903(2002)



Partonic collectivity at RHIC

1) Copiously produced hadrons freeze-out: Tfo = 100 MeV, T = 0.6 (c) > T(SPS)

2)* Multi-strange hadrons freeze-out: Tfo = 170 MeV (~ Tch), T = 0.4 (c)

3)** Multi-strange v2: Multi-strange hadrons and flow!

4)*** Constituent quark scaling: Seems to work for v2 and RAA (RCP)

Partonic (u,d,s) collectivity at RHIC



SummarySummary

(1) Flavor equilibration - necessary for QGP

(2) Jet energy loss - QCD at work

(3) Collectivity - pressure gradient ∂PQCD

Deconfinement and Partonic collectivity

First time ever, re-produced partonic matter in the laboratory since big bang.


//Nxu/tex3/TALK/2004/08CCAST PPhase diagram of strongly hase diagram of strongly

interacting matterinteracting matter

CERN-SPS, RHIC, LHC: high temperature, low baryon density

AGS, GSI (SIS200): moderate temperature, high baryon density

GSI200GSI200

RHICRHIC

LHCLHC

Discover QGP and more!



Some Future reading:Some Future reading:

- http://qm2004.lbl.gov/

- Quark Matter conference proceedings 2002 Nucl.Phys. A715, 1c(2003).

- Quark Matter conference proceedings 2001 Nucl.Phys. A698, 1c(2002).

- “Introduction to High Energy Heavy Ion Collisions’’ - By C.Y. Wong (Oak Ridge),. 1995. Singapore, Singapore: World Scientific (1994) 516 p.

- “Introduction to Relativistic Heavy Ion Collisions’’ - By L.P. Csernai (Bergen U.),. 1994.

Chichester, UK: Wiley (1994) 310 p.

- Recent discussions on the QGP discovery http://www.bnl.gov/riken/May14-152004workshop.htm



Documents

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 1 Nu Xu Lawrence Berkeley National Laboratory Part I: QM04 Highlights (experiment) Part