RHIC Experimental Status&

Future Outlook

Huan Zhong Huang

Department of Physics and Astronomy

University of California, Los Angeles

June 28-29 @ Shanghai Eastern Forum

Topics

1) Deconfined Partonic Matter

2) What Can Heavy Ion Physics ExperimentalistsTeach About Lattice QCD?

3) Is There a Phase Transition?

4) Chiral Symmetry Restoration?

5) RHIC as an Exotic Particle Factory

Constituent Quark Scaling

STAR

PHENIX

Baryon

Meson

Constituent (n) Quark Scaling-- Meson n=2 and Baryon n=3 grouping

Saturation of v2 at Intermediate pT

Partonic v2 and Surface Emission

PR

L 92

(20

04

) 05

23

02

; PR

L 91

(20

03

) 18

23

01

At hadron formation time there is a collective v2

among constituent quarks

Recombination/coalescence provides a hadronization scheme (not necessarily related to partonic matter, works for d+Au)

Possible geometrical nature of v2 saturation – surface emission

Hadronization of Bulk Partonic Matter

1) At the moment of hadronization in nucleus-nucleus collisions at RHIC the dominant degrees of freedom is related to number of constituent quarks.

2) These ‘constituent quarks’ exhibit an angular anisotropy resulting from collective interactions.

3) Hadrons seem to be formed from coalescence or recombination of the ‘constituent quarks’, and the hadron properties are determined by the sum of ‘constituent quarks’.

Conditions at Tc

Empirically,Partonic matter evolves such that at the

hadronization, the dominant degrees of freedom are in ‘constituent quarks’/quasi-hadrons. The formation mechanism could be coalescence or recombination of these quarks.

Gluon degrees of freedom are not manifested at hadronization, though at initial stage of the heavy ion collision, gluons must dominate.

Lattice QCDLQCD,

Spectral functions of hadrons (J/psi and light hadrons) survive near TC or somewhat above TC. Strong correlations persist up to high temperature above TC!

LQCD e.g. S. Datta et al, hep-lat/0412037 J/ and C may survive up to 2.25 TC !

Our data indicate that at T=TC even light hadrons are in quasi-hadron state (strongly interacting constituent quark state) !

Phase Transition ?

The Initial State from the Collision must be dominated by gluons (Temperature?) Parton Evolutions (?)At the Hadronization Stage the dominate degrees of freedom are constituent quarks (or quasi-hadrons) (Empirical + LQCD)What is the parton evolution dynamics??

Empirically the dense matter with collective motions of constituent quark degrees of freedom must be preceded with a deconfined partonic matter, BUT we do not have any experimental indication that this is a phase transition !

Chiral Symmetry

How Chiral Symmetry has manifested innucleus-nucleus collisions?

We must measure vector mesons in both hadronic and leptonic decay channels!

electron PID TOF upgradeHFT – reduce conversion BK

K-pi PID TOF upgradeand ’ EMC + high statistics

Baryonic resonances ()....)

RHIC Physics in + Years

1) Heavy Quark Production-- Yield and pT distribution (Energy Loss)-- Parton Collectivity

2) Thermal Photon Radiation

3) QCD Photons (gamma-jet and QGP Brem.)

4) Chiral Symmetry and low mass di-leptons

5) Exotic Particle Searches

RHIC – Exotic Particle FactoryClustering and Surface Emission

Volcanic mediate pT – Spatter (clumps)

Enhancement of Clustersat intermediate pT !

Search for Multi-quark (>3) Cluster State at RHIC !

dAu results

M (GeV/c2)

pK+ and pK- from 18.4 M d+Au at 200 GeVBackground – Combinatorial and Correlated Pairs

dAu results

Understand the Background!

PeaK?!

dAu results

The invariant mass distribution is fitted to a Gaussian plus a linear function. A 3.5-5.0 sigma signal is seen Measured mass is about 1.53 GeV/c2. Full width is about 15 MeV

The Puzzle Continues1) If pK+ peak at 1530 MeV/c2 is a real pentaquark, then

I = 1 likely, there must be a +. But the recent JLab null result on + casts serious doubt on the observation

of +.

2) The STAR observed yield is so small such that many experiments would not have the sensitivity to see it.

3) Within the STAR data we have not seen any significantpeak signal in p+p (8M) data and Au+Au at 200 GeV (~10M).What do these null observations mean?Production dynamics or data set bias unknown to us?What is so special about d+Au 200 GeV (18.4 M events)

and Au+Au 62.4 GeV (5.1 M events)?

Other Exotic Particles

Gluon Balls

Exotic mesons (uds)(ud) (uds)s

Pentaquarks

DibaryonsH (uuddss)[ (ssssss)

STAR – Exciting Physics Program A full TOF and Heavy Flavor Tracker upgrade will greatly enhance STAR’s capability !!

RHIC – Exotic Particle Factory

Heavy Flavor TrackerUsing Active Pixel Sensor

two layers of thin silicon detector 1.5 cm and 4 cm radius Charmed Exotics?!Full Barrel TOF Using MRPC

eRHIC Inevitable ?! But When?RHIC II – Machine Upgrade

-- Tandem-- Electron Cooling

Electron – LINAC 10 GeV

Natural Physics Direction from RHIC/JLAB20 Years ?

RHIC Beyond +5 Years Hadrons with internal structure beyond existing

QCD qqq and q-qbar framework !!

pp pA

AA

pppA

AA

Exotic

RHIC – Dedicated QCD Machine & Beyond

(spin) (CGC,EMC)

(Deconfinement Phase Transition)

The End

Identified ParticlesNo Clear Idea on what to measure for

phase transition signatures !

Particle Flavor FluctuationsStrangenessBaryon numbersBaryon Formation Mechanism?Hadronization time scale?

STAR Full TOF Upgrade will open a newwindow. Is it sufficient to see a clear picture? ??

Deconfined Matter at RHICCoalescence/Recombination Mechanism

IS not key argument for deconfinement !It works in d+Au and perhaps p+p as well !

Deconfined –Constituent quark degree of freedom

Matter – Collective interaction partonic v2

strange/charm dynamics in the deconfinedmedium

Is There a ++ Pentaquark State?

Require the opening angle of the two daughters to be greater than 30 degree, and change the proton p&pt cut to be within 0.3 and 1.5 GeV A clear peak is seen with a 5-6.4 sigma significance

4.6211200/2902/ NS

d+Au

Is Isospin One ?

If both + and ++ exist as the lowest pentaquark state –Isospin >= 1

Chiral Soliton ModelDi-quark modelQuark cluster model???

If state has isospin I = 1, there will be0 n + KS

Critical confirmation for I = 1 !!

RHIC’s Uniqueness

Multi-Strange Exotic Particles:

M1890-180*Y] MeV

RHIC: Large StrangenessProductionStrangeness s ~ 1baryon and anti-baryon

~ symmetric

NA49 Pentaquark ?- - - + -

What Are RequiredHigh Detection Efficiency for Weak Decays

-- Intermediate Tracking R~10 cm up-- Continuous Tracking a plus

Large Acceptance-- Ks, Lambda, Xi, Omega-- Multi-particle Correlations

Neutral Detectors-- Neutron (anti-neutron!)-- 0

PID – TOF and trigger capabilityMicro-Vertex– for Charmed Exotic ParticlesHigh Rate Capability and DAQ Rate

New Experiment

Affordable Neutron Detector

Tracking of V0 near primary vertex

Excellent Particle Identification (TOF)

Upgradeable with Heavy Flavor Tracker

STAR versus New ExperimentSTAR: Existing detector

Large AcceptanceReasonable Data Rate

V0 Capability not ideal-- lack of continuous tracking

at intermediate RNo Neutron detectionPID – TOF will doLimited high rate (distortion)Large Inertial in STAR