Perspectives on RHIC-II:Heavy Ions and Hot+Dense Matter

Ralf RappTexas A&M University

1. RHIC-II Science WorkshopBNL, 19.11.04

Introduction I: Hot and Dense QCD2

41

aq Gq)m̂Agi(q QCDL + Thermal Field Theory

pQCD: p>>T energy loss

non-pert QCD: p~T equation of state

2GeV<p<6GeV hadronization

medium probe (1) cluster (2-3) medium response (1000)≈20GeVfm-3 quark scaling thermal, 0≈0.5fm/cD≈0.7GeV

nonabelian?! Mass/binding? phase transition?

RAA(pt)v2(pt/n) / n v2(pt,m)

Thermalization at RHIC study: • chiral symmetry restoration• deconfinement• spectral properties of matter

Introduction II: Exploring the Phase Diagram

1.0 T/Tc

m‹qq›-

T=1.4Tc

Genuine properties of QGP!Direct link to lattice QCD!

[Bielefeld] L

L

[Tokyo]

2.) Early Phases Matter Composition and Temperature 3.) QGP at p››T Nonabelian Effects Energy Deposition

4.) QGP at p~T Degrees of Freedom and Interactions Deconfinement

5.) Chiral Symmetry Restoration Order Parameters and Observables Medium Modifications of Hadrons

6.) Other Puzzles and Opportunities 7.) Concluding Remarks

Outline

2.) Early Matter Composition[Hirano+Nara ‘04]

Initial State: CGC!? (fwd y)

• QGP (=47cT4) or GP (=16cT4)• qq production (CGC, sphalerons)• thermalization at 0≤ 0.5fm/c• initial temperature

Electromagnetic Diagnostics: • photons and dileptons gq→q ~ g q

qq→ee ~ (q )2

• thermal window: q0 , Mee≈ 1-3GeV• pre-equilibrium contribution?!

3.1 Energy Loss

Eg/Eq=9/4 +increasing gluon content with √s

3.) Probing the QGP with high pt

RA

A(p

t=6G

eV)

√s [GeV]

• L2-DependenceAlready observed in DIS on nuclei [HERMES]

RHIC: medium expansion + centrality dependence L2

• Non-Abelian Charge

• Heavy Quarks mQ provides extra scale to disentangle, e.g., screening mass D

• Energy Gauge: high-pt photon tag; RAA(pt→∞)→1 ?!

[Wang ’04]

[Kharzeev+Dolshitzer, Djordjevic etal]]

[Vitev ’04]

Cone angle of shock frontcosemis = cs/c em=±(55º-63º)emis

[STAR]pT=(0.15-4)GeV

3.2 Energy Deposition and Correlations

Track “lost” energy: • thermalization?• correlations as advanced tests of coalescence [Hwa etal, Fries etal]• sonic shock wave in the hydrodynamic medium: [Shuryak]

4.) The Thermal Nature of QGP4.1 Light-Quark SectorHydrodynamics requires early equilibration. How?

Potential scenarios: (i) pQCD + ?! (ii) sQGP: heavy q, g + (many) boundstates (iii) q, g + (few) resonances

large imaginary parts required (liquid: M~ vs. plasma: <<T)

(i) Perturbative QCD Rescattering• “anomalously” large width ~g2T• gg↔ggg rescattering [Xu+Greiner ’04]• nonabelian plasma instabilites [Moore etal ’04]

(ii) Heavy Partons + Multiple Bound States→ based on finite-T lattice potentials approach to “zero-binding line” ~ stable-mass-resonance

[Shuryak,Zahed, Brown, …]

• thermal parton scattering through bound states?• composite interactions? quark scaling?

Dilepton Radiationratio to pert. qq rate

Mee/mq

_

(iii) “Hadronic” Resonances (few, colorless) • “moderately” heavy q+g, rescattering above threshold; • “hadron” formation above Tc → generalize coalescence • check with open heavy flavor

• dynamical origin of resonances? cc production? • onset of pQCD regime: pt>5-6GeV ? open bottom?

_ [Müller etal ’95, Molnar’04]

[van Hees+RR ’04]

Thermalization + “D”-Mesons

pQCD

“D”

Ellitpic Flow + Coalescence

jet- quench[Djordjevic etal ’04]

4.2 Quarkonia: Direct vs. Regeneration QCD Lattice: J/ up to ~2Tc in QGP J/ + g c + c + X←→ -

]NN[d

dN eq

)T/)mmexp[()m/m()N(N c

/ccc

eq 2232

: inelastic reaction rate (width)

• c-quark equilibration?• Deconfinement order parameter? Width?!

[Grandchamp etal]

Centrality Dependence

[Thews]

Rapidity Spectra

mc *

y

J/ Excitation Function

(ii) Scrutinizing Charmonium Regeneration J/ Elliptic Flow

Furthermore: Bottomonium suppression?! ’ (sensitive to in-medium D-mesons)

Suppression only Thermal Coalescence at Tc

[Wang+Yuan ’02][Greco etal ’04]

MB Au-Au

Factor ~5 different! Transition in pt!?

5.) Chiral Symmetry Restoration

~ “- a1(1260)” (chiral partners)

Axial-/Vector in Vacuum

pQCD cont.

)Im(Ims

dsf AV

2

Order parameters: <qq> , f, mq* ↔ Relation to observable?

)T(fMqxdd

dN Bee23

2

44

Imem ~ [ImD+ImD/10+ImD/5]

Low-Mass Dilepton Rate:-mesondominated!

at Tc: Chiral

Restoration

-

Hadronic Many-Body Theory

5.2 Vector Mesons at RHIC

• baryon effects important even at B,net=0 : sensitive to B,tot=+B , most pronounced at low M • more robust ↔ OZI

-

Dilepton Emission Rates

Quark-Hadron Duality ?!in-med HG ≈ in-med QGP !

[qq→ee][qq+O(s)]

--

5.3 Dileptons I: Lessons from SPS

New Data (preliminary)

• enhancement concentrated at low (pair-) pt , theory low? • signal increases with ~ (Nch )2 • mass region between and

8% centralpt

e >100MeV

5.3 Dileptons II: RHIC

• low mass: thermal! (mostly in-medium )• connection to Chiral Restoration: a1 (1260)→ , 3• int. mass: QGP vs. cc → e+e-X, softening due to rescatt.? (v┴!)-

[RR ’01]

[R. Averbeck, PHENIX]

QGP

5.4 Resonance Spectroscopy

Dilute matter, but versatile:• -meson: m=-50MeV and/or broad. + thermal PS + BE ?• →

: threshold strength? (↔)• baryons! ++→+p, N(1535)→N,… • reliable freezeout treatment (transport)

[STAR]

[Florkowski etal, Brown+Shuryak]

Theoretical Opportunities: • ↔ 0++-glueball mixing, connects ‹qq› ↔ ‹L› • interacting hadronic EoS: (B,T) - chem. freezeout - order parameter:

D

C

Temperature T →

Qua

rk M

ass m

q

→

QCD

mG→0

m→0

[Fukushima]

h hq

h

q mΩ

mm

mΩ

qq

6.) (Some) Other Puzzles and Opportunities

• constituent quark scaling accidental? [Molnar]

• HBT: early QGP push + pos. x-t correlation? [Lin+Ko ‘02]

• exotic particles: + [Nonaka etal ’04] ,Bc [Thews ‘99] , glueballs ?

• global QGP polarization at finite b? [Wang ’04]

• P, CP violation (UA(1) restoration)? [Kharzeev ’04]

…

7.) Summary• RHIC-II unique (dedicated) facility to unravel genuine (nonpert.) QCD properties of the QGP: - nonabelian energy loss (high-pt) - bound states / resonances (IM-dileptons, open charm) - deconfinement (quarkonia; width?! J/ -regen, -supp) - chiral symmetry restoration (LM-dileptons, resonances) mostly rare probes (incl. excitation functions)• importance of precision data + theory (redundancy) to disentangle mechanisms

very exciting opportunities ahead …

4.2 Direct Photons and Dileptons

),(1023

2

4 TqfMqd

dR Bee

),( 0230 Tqfqd

dRq B

Sources:• Initial hard scatt.: Drell-Yan / Compton (tag jets! [Gale])• Pre-equilibrium: Radiation off jets [Gale] , rescatt.+fragment. of secondaries (parton cascade [Bass])• Thermal:

Im Πem(M,q)

Im Πem(q0=q)

e+

e-

γe.m. correlator

chemical off-equilibrium: QGP: q,g ≤ 1 HG: ,K,.. > 0

[Niemi,Moore]

Direct Photons at SPS and RHIC

• large “pre-equilibrium” yield from parton cascade (no LPM)• thermal yields ~ consistent• QGP undersaturation small effect

• pQCD Cronin ~ π0

T0≈205MeV sufficient• new WA98 points: -Bremsstr. via soft ?

[Turbide etal]