What have we learned from RHIC , So far?

RHIC has taken data in:2001: AuAu (130GeV)2002: AuAu , pp(200 GeV)2003: pp, dAu (200 GeV)

Any nucleus on any other.Top energies (each beam):

100 GeV/nucleon Au-Au.250 GeV 2 counter-circulating rings, 3.8 km circumferencepolarizedpolarized p-p.

PHOBOS Detector 2003

SPECTRIG

T0

T0

mini-pCal

pCal

i. Moved TOF walls back

• 5 m from interaction point

ii. New on-line high pT Spectrometer Trigger

iii. New “time-zero” (T0) Cerenkov detectors

• On-line vertexing and ToF start time

iv. Forward proton calorimeters on Gold and Deuteron sides

v. DAQ upgrade (x10)

95° 30°

30°15°

2.3°

STARSTAR

BRAHMS

PHENIX

Russia:MEPHI - MoscowLPP/LHE JINR - DubnaIHEP - Protvino

U.S. Laboratories:ArgonneBerkeleyBrookhaven

U.S. Universities: UC BerkeleyUC DavisUC Los AngelesCarnegie Mellon Creighton UniversityIndiana UniversityKent State UniversityMichigan State UniversityCity College of New YorkOhio State UniversityPenn. State UniversityPurdue UniversityRice UniversityTexas A&MUT AustinU. of Washington Wayne State UniversityYale University

Brazil: Universidade de Sao Paulo

China: IHEP – BeijingIMP - LanzouIPP – WuhanUSTCSINR – ShanghaiTsinghua University

Great Britain: University of Birmingham

France:IReS StrasbourgSUBATECH - Nantes

Germany: MPI – MunichUniversity of Frankfurt

India:IOP - BhubaneswarVECC - CalcuttaPanjab UniversityUniversity of RajasthanJammu UniversityIIT - BombayVECC – Kolcata

Poland:Warsaw University of Tech.

The STAR Collaboration

High Density QCD Matter in Laboratory

Determine its properties

QCD Prediction: Phase Transitions

Deconfinement to Q-G Plasma

Chiral symmetry restoration

Relevance to other research areas?

Quark-hadron phase transition in early Universe

Cores of dense stars

High density QCD

Phases of QCD

Preliminary sNN = 200 GeV

Uncorrected

participants

spectators

peripheral (grazing shot)

central (head-on) collisionCentrality classes based on mid-rapidity multiplicity

Npart (Wounded Nucleons) ~ soft production

Nbin ~ hard processes

Centrality and Participants in HI

5% central

15% Central

Au AuZDC ZDC

•Symmetric Zero Degree Calorimeters

•Central Trigger Barrel

Triggering Capabilities

Understanding “Bulk” MatterStudying Matter:

– Global Observables Nch, ET, pT

, S, …

– Particle Yields & Ratios

Tch, B, S, …

– Particle Spectra Tfo, flow, stopping,

…– Correlations– … and all that in pp,

pA, AA

STAR preliminary

99.5%

Rapidity Density600 1200

PHOBOS Central Au+Au (200 GeV)

Compilation by K. Eskola

• Multiplicity at low end of range– But: Energy density 30x nuclear

matter

• Most models didn’t do so wellPHOBOS multiplicity papers:

Phys. Rev. Lett. 85 , 3100 (2000)

Phys. Rev. Lett. 87, 102303 (2001)

Phys. Rev. C 65 , 31901R (2002)

Phys.Rev. Lett. 88 , 22302 (2002)Phys. Rev. C 65 , 061901R (2002) nucl-ex/0210015, PRL in Pressnucl-ex/0301017, subm. to PRL

Particle Production

RHIC: Nch at mid-rapidity

Consistency of RHIC resultsPHENIX: PC, STAR: TPC

PHOBOS: Si BRAHMS: Si & Scint.

PHENIX & STARpreliminary

Ratio R(200/130):BRAHMS: 1.14 0.05PHENIX: 1.17 0.03PHOBOS: 1.14 0.05STAR: 1.19 (no sys. yet)

Nch(sNN) – Universality of Total Multiplicity?

• pQCD e+e- Calculation

)/exp( sBsch CAN

Total charged particle multiplicity / participant pair

Accidental, trivial? Is plain parton fragmentation all there is in AA above s ~ 20 GeV?

(A. Mueller, 1983)

2/sseff

Same for all systems at same s(seff for pp)

Nch: Centrality Dependence at RHIC (SPS)

_pp

PHOBOS Au+Au ||<1

19.6 GeVpreliminary

130 GeV

200 GeV

Au+Au

(preliminary)

Everything counts:• Nch|=0 described nicely by KN (hard + soft)• Nch scales with Npart

collpp

partpp

Nxn

Nnx

d

dN

2

)1(

Rapidity Spectra: Boost-Invariance at RHIC ?

M. Baker (PHOBOS)

D. Ouerdane (BRAHMS)

1cosh)/(

cosh)/(),( :Jacobian

22

mp

mpp

y

ET/ Nch from SPS to RHIC

Independent of energyIndependent of centrality

PHENIX preliminaryPHENIX preliminary

Surprising fact: SPS RHIC: increased flow, all particles higher pTstill ET/ Nch changes very littleDoes different composition (chemistry) account for that?

Ratios, Ratios, Ratios ….• Huge amount of results from all 4 RHIC experiments:• systematic studies of: -/+, K-/K+, p/p/ ,/,/,

/p, K/ , /, /h, K, K*/K, …– many as function of pT, Npart

– at s of (20), 130, and 200 GeV– with and without feed-down correction ()

• BRAHMS large y coverage and reach to high pT

• PHENIX reach to high pT

• STAR multi-strange baryons

NEW: Rapidity dependence of ratios at RHIC

BRAHMS 200 GeV

At mid-rapidity:Net-protons: dN/dy 7proton yield: dN/dy 29 ¾ of all protons from pair-production

p/

• Proton yield is comparable with pions @ 2 GeV in central collisions, less in peripheral

Central

Peripheral

Statistical Model: First Look at AuAu @ 200 GeV

Predictions:phenomenologically: B ~ 1.3 GeV (1+s/4.5 GeV)-1

assume unified freeze-out condition: E/N ~ 1.1 GeV T

Statistical Models: from AGS to RHIC

Fit by Beccatini using total yields from NA49hadron gas fit with partial strangeness saturation

Different implementation ofstatistical model (Kaneta/Nu,Beccatini, PBM et al., …)

Fact: all work well at AGS, SPS and RHIC

Slight variations in the models, but roughly:

Tch [MeV] B [MeV]

AGS 125 540

SPS 165 250

RHIC 175 30

Does the success of the modeltells us we are dealing indeed with locally chemically equilibrated systems? this+flow If you ask me YES!

Anisotropic flow from AGS to RHIC

Outline:1. Directed flow

(techniques, models, results)2. Elliptic flow

(techniques, models, results)3. Elliptic flow at high pt’s.4. Open questions

...) φ) ( v ) (φ v (dy dpN d

dφ dy dpN d

t t

2 2 2 121

2 1

2 3

cos cosπ

Directed flow Elliptic flow

Anisotropic flow correlationswith respect to the reaction plane

X

Z b

XZ – the reaction plane

Picture: © UrQMD

What flows and when?

<pT> prediction with Tth

and <> obtained from blastwave fit (green line)

<pT> prediction for Tch = 170 MeV and <>=0pp no rescattering, no flowno thermal equilibrium

STAR

preliminaryF. Wang

and appear todeviate from commonthermal freeze-out Smaller elast? Early decoupling from expanding hadronic medium? Less flow?What’s about partonic flow?