present and future perspectives of relativistic heavy-ion collisions 고려대학교 홍 병 식

Present and Future Perspectives of Relativistic Heavy-Ion Collisions

Present and Future Perspectives of Relativistic Heavy-Ion Collisions

고려대학교 홍 병 식

2003년 10월 8일 서울대학교 콜로퀴움 2

Motivation of HI Collisions

Investigating the QCD prediction of a deconfined (& chiral symmetry restored) high-energy-density phase of nuclear matter

QGP is thought to have existed ten millionths of second after the Big Bang; creating the primordial matter of universe in the laboratory.

High-energy nuclear collisions will compress and heat the heavy nuclei so much that their individual protons and neutrons overlap and lots of pions arise, creating the Quark-Gluon Plasma (QGP)


Quark-Gluon Plasma Quark-Gluon Plasma

Big BangBig Bang

EW & QCD Separate EW & QCD Separate (GUT ) (GUT )

WI & QED SeparateWI & QED SeparateHe FormationHe Formation

Atom Formation Atom Formation

Galaxy & Star Formation Galaxy & Star Formation

First SupernovaeFirst Supernovae

Present Present


Heavy-Ion Collisions

Some of the energy they had before is transformed into heat and new particles right here !

Approaching99.95% c

Collisions Passingthrough

Expansion


Phases of Nuclear Matter

T(MeV)

Density(n0)

~150

~10

Early Universe(RHIC, LHC)

Color SuperconductorNeutron Star

Hadron Gas

Quark-Gluon Plasma

Phase Transition

Atomic Nuclein0=0.17/fm3

1 fm=10-15 m

1 MeV~1010 K


Heavy-Ion Accelerators

Acceleratorc.m. Energy

(GeV)Status

SIS 18(GSI, Germany)

2A(A=mass number)

Running

AGS(BNL, USA)

5A Finished

SIS 200(GSI, Germany)

8AJust approved; Plan to run from ~2010

SPS(CERN, Switzerland)

20A Finish soon

RHIC(BNL, USA)

200A Running since 2000

LHC(CERN, Switzerland)

5500APlan to run from

~2007


Relativistic Heavy Ion Collider

Brookhaven National Lab.Brookhaven National Lab. in New Yorkin New York

Circumference: 3.83 km First collision: 2000 100A GeV Au+Au(2X1026/cm2/s) 250 GeV p+p(2X1032/cm2/s)


More

ab

ou

t the

More

ab

ou

t the P

HEN

IXP

HEN

IX

PHENIX= Pioneering High Energy Nuclear Interaction eXperiment


PHENIXPHENIX the Reality the Reality May 2001


Shopping ListShopping List

1. DeconfinementR() ~ 0.13 fm < R(J/) ~ 0.29 fm < R(’ ) ~ 0.56 fm (Electrons, Muons)

2. Chiral Symmetry RestorationMass, width, branching ratio of to e+e-, K+K- with M < 5 MeV (Electrons, Muons, Hadrons)Baryon susceptibility, color fluctuations, anti-baryon production (Hadrons)DCC’s, Isospin fluctuations (Photons, Charged Hadrons)

3. Thermal Radiation of Hot GasPrompt , Prompt * to e+e-, +- (Photons, Electrons, Muons)

4. Strangeness and Charm ProductionProduction of K+, K- mesons (Hadrons)Production of , J/, D mesons (Electrons, Muons)

5. Jet QuenchingHigh pT jet via leading particle spectra (Hadrons, Photons)

6. Space-Time EvolutionHBT Correlations of ± ±, K± K± (Hadrons)

Summary: Electrons, Muons, Photons, Hadrons


12 nations 57 institutes 460 people


Selected Results

• Global Features– Particle Multiplicity– Transverse Energy– Flow

• Identified Particles– Hadrons– Electrons

• Studied vs– Centrality– System Size – Beam Energy

All results presented here are for p+p & Au+Au

collisions at =130 and 200 GeVNNs


Particle Multiplicity

• PHOBOS Compilation (PRL 88, 022302 (2002))• HI is producing more particles than elementary p-p or

p-pbar at the same beam energy

Npart = # of participant nucleons


Event Charaterization

• Use the combination of– Zero Degree Calorimeters (energy of unbound spect

ator neutrons)– Beam-Beam Counters (cha

rged multiplicity)– to define centrality classes

• Use – Glauber Modeling– to extract the number of participants

0-5%5-10%

10-15%etc.

Centrality Collisions Participants

0-5% 945 15% 347 15%

5-15% 673 15% 271 15%

15-30% 383 15% 178 15%

30-60% 123 15% 76 15%

60-80% 19 60% 19 60%

80-92% 3.7 60% 5 60%


Global Variables

28.088.0 A12.034.0 B19.038.0/ AB

)(24.080.0 GeVA )(09.023.0 GeVB

18.029.0/ AB

Yields grow significantly faster than Npart

Evidence for the hard scattering (Nbin) term

ch binpart0dN d A N B N

Phys. Rev. Lett. 86, 3500 (2001)

First PHENIX paper


Gluon Saturation?

r/ggg

Eskola, Kajantie, and Tuominen: hep-ph/0009246Kharzeev, Nandi: nucl-th/0012025

Gluon begins to fuse with high enough gluon density; limit the particle production

Gluon Saturation does not set in for peripheral collisions: need to look for the central collisions


Initial Energy Density Bjorken’s 1-D hydrodynamic model

dy

dE

RdyR

dE

dzR

dE

V

E T

TT

T

T

T

222

1~~ ~4.6 - 23 GeV/fm3

2%

26T39

y 0

dE578 GeV 1.19 0.01

dy

PRL87, 52301 (2001)

Time to thermalize the system(~1.0 - 0.2 fm/c?)

Energy deposition is certainly large enough to reach the QGP

Latticec

Bj~ 4.6 GeV/fm3

J. Nagle

Bj~ 23.0 GeV/fm3


QGP Probes

• Expectation– quarks and quarkonium states may respond differently to a pl

asma compared to ordinary nuclear matter

• Hard Probes– Formed in initial collisions with high Q2

– Calculable in pQCD given • Parton strunture function• Hard scattering rate• Fragmentation function

q

q

Hadron jet

Hadronjet


Partonic Energy Loss in QGP

q

q

Baier, Dokshitzer, Mueller, Schiff, hep-ph/9907267Gyulassy, Levai, Vitev, hep-pl/9907461Wang, nucl-th/9812021and many more…..

Partons are expected to loose energy via gluon radiation in traversing a QGP(jet quenching)

Hadrons above pT > 2 GeV expected to be from jet fragmentationLook for a suppression of leading hadrons in that pT region


Other Nuclear Effects

Au

pAu

1=

pAuppA

R

Prediction for RHIC

They enhance the high pT hadrons

soft/hardtransition?

Cronin Effect +Shadowing


Hadron Spectra at 130A GeV

Central

Scaled pp

Peripheral

Peripheral

Central

Scaled pp


Suppression Observed• ratio of pT-spectra

– AA central / pp

RAA d 2N AA dydpT

d 2N pp dydpT NcollAA

• RAA =1 for scaling with number of binary collisions

• RAA < 1 for central reactions at 130A GeV– observed in neutral

pions and charged hadrons (PHENIX and STAR)

Phys. Rev. Lett. 88, 022301 (2002)


Comparison with SPS Data• RAA > 1 for reactions

at SPS and ISR

WA98, Eur.Phys.J.C 23, 225-236 (2002)


Data vs Theory

Shadowing+ Cronin

Energy Loss

Scaled pp

Peripheral data

Central data

Energy Loss

Shadowing+ Cronin

Scaled pp

<dE/dx>=7.3 GeV/fm 15x higher than incold nuclear matter (HERMES)X.N. Wang PRC 61, 064910 (2000) E. Wang & X.N. Wang, hep-ph/0202105

Central data


New Results at 200A GeV

pp and AA measured in the same detector


Suppression

• strong suppression in 0:– decreasing with pT

– factor 6 at pT = 6-8 GeV/c

• similar suppression in charged hadrons– RAA slightly higher at

intermediate pT?

• discrepancies in charged RAA between experiments– Glauber calculations?– NN-reference?

• better consistency between STAR and PHENIX

for central/peripheral!

PHENIX, PRL 91, 072301 (2003)


Jet Correlation at RHIC• Establish near-side

(trigger-jet) and far-side (counter-jet) correlation in pp

• Ansatz: correlation in AA as superposition of pp data and elliptic flow– pp signal from pp data– elliptic flow from reaction

plane analysis

• quantify deviations from pp by integrals around = 0 and

• back-to-back correlation disappears in central AuAu

C2(Au Au ) C2(p p) A * (1 2v22 cos(2))

PRL 90, 082302(03’), STAR Collaboration


d+Au Control Experiment

• Collisions of small with large nuclei were always foreseen as necessary to quantify cold nuclear matter effects.

• Recent theoretical work on the “Color Glass Condensate” model provides alternative explanation of data:– Jets are not quenched, but are a priori made in fewer numbers.– Color Glass Condensate hep-ph/0212316 by Kharzeev, Levin, & Nardi

• Small + Large distinguishes all initial and final state effects.

Nucleus-nucleuscollision

Proton/deuteron-nucleus collision

VS.


d+Au Spectra

• Final spectra for charged hadrons and identified pions.• Data span 7 orders of magnitude.


RAA vs. RdA for Identified 0

d+Au

Au+Au

Initial State Effects Only

Initial + Final

State Effects

d-Au results rule out CGC as the explanation for Jet Sud-Au results rule out CGC as the explanation for Jet Suppression at Central Rapidity and high pppression at Central Rapidity and high pTT


Charged Hadron Results• Striking difference of d+Au and Au

+Au results.• Charged Hadrons higher than neutr

al pions.

Cronin Effect:

Multiple Collisions broaden high PT

spectrum


Centrality Dependence

• Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control one.

• Jet Suppression is clearly a final state effect.

“PHENIX Preliminary” results, consistent with PHOBOS data in

submitted paper

Au + Au Experiment d + Au Control Experiment

Preliminary DataFinal Data


Summary at Present1. RHIC collisions produce more particles and energy th

an ever produced.2. There is an evidence that the dense matter behaves c

ollectively.3. Fireball is close to the condition for early universe in t

he energy density estimate and antiproton/proton ratio ( > 0.6).

4. Jet quenching is observed with high pt single hadrons and jet correlations (Cronin in d+Au).

5. First spectra for electron and implications for charm production.


Future • Establish that the QGP is formed via

– Blackbody radiation from hot QGP – Presence of color Debye screening of QGP

• Explore the energy and system size dependences• Spin structure function of antiquarks and gluons by po

larized proton collisions

• Future Project– CBM/SIS200/GSI heavy-ion collisions

• Explore the highest baryon density nuclear matter– CMS/LHC/CERN heavy-ion collisions

• b production via muon detection and jet production


Exploring Nuclear Matterat the highest-density

B. Friman et al.,Eur. Phys. J. A3, 165(1998)


Motivation-Strangeness

When this enhancement of hyperons starts?

QGP already at 30A GeV?

Unique maximum in AA


Motivation-e+e- pair


Motivation-Charm

SIS18: strangeness production near threshold (1-3 n0)SIS200: charm production near threshold (5-10 n0)In-medium effects


More Motivations

• Indications for deconfinement at high baryon density– Anomalous charmonium suppression

• Temperature of Hot Nuclear Matter– Virtual photons decaying into e+e- pairs

• Equation-of-State– Flow measurement (direct, v2, radial, etc.)

• Critical Point– Event-by-Event fluctuations

• Color Superconductivity– Precursor effects at T > TC


How?

• Accelerator Side– Require high intensity for rare particle measurements: ~109 i

ons/sec (cf. ~107 ions/sec at the SPS)– High spill fraction: 0.8 (cf. 0.25 at the SPS)

• Detector Side– Identification of hadrons at high momentum with high track d

ensity environment (~1000 for 25A GeV Au+Au)– Identification of electrons with pion suppression by 104 – 105

(need two electron detectors)– Reconstruction of particle vertices with high resolution– Large acceptance


2nd Generation Fixed Target Exp.

• Magnetic field: 1-2 T• Silicon Pixel/Strip: hyp

erons and D’s• RICH: electrons, high

momentum pions & kaons

• TRD: electrons from the J/Psi decay

• TOF– Start: diamond pixel– Stop: RPC

CBM Detector Concept


Future Facility at GSI

HADES at 2-8A GeV

CBMat 8-40A GeV


What is LHC?

• 100 m underground• 9 km diameter• 27 km circumference• Use the already existed

LEP tunnel • Run p-p collisions from 2

007• Run Pb-Pb collisions fro

m about 2007


CMS (Compact Muon Solenoid)


Korea in CMS

KoreaItaly

FRPC Total Area 1,400 m2


Korean RPC: Beam Test at CERN

2001 Test Setup


Korean RPC: Performance Summary

Characteristics

CMS Requirement

sTest Results

Time Resolution < 3 nsec < 1.5 nsec

Efficiency > 95 % > 95 %

Rate Capability > 1 kHz/cm2 > 1 kHz/cm2

Noise Rate < 15 Hz/cm2 < 15 Hz/cm2

Plateau Region > 300 V > 400 V


More Details• Beam test results of a large forward resistive plate chamber for the CMS/LHC, N

ucl. Instum. Methods A443, 31 (2000)• Temperature and humidity dependence of bulk resistivity of bakelite for resistive

plate chambers in CMS, Nucl. Instrum. Methods A451, 582 (2000)• Study on the operational conditions of a double gap resistive plate chamber for t

he CMS, Nucl. Instrum. Methods A456, 29 (2000)• Beam test results of a large real size RPC for the CMS/LHC experiment, Nucl. Ins

trum. Methods A456, 23 (2000)• Aspects of operational conditions of a double gap prototype RPC for the CMS/LH

C experiment, Nucl. Instrum. Methods A465, 447 (2001)• Performance of a large forward resistive plate chamber for the CMS/LHC under hi

gh radiation environment, Nucl. Instrum. Methods A469, 323 (2001)• Threshold dependence of strip clusters for the forward region resistive plate cha

mber of the CMS/LHC experiment, Nucl. Instrum. Methods A (2002) in print.• More in preparation.


Conclusions

• Since HI experiments started at the AGS and SPS in 1986, relativistic heavy-ion collision has been one of the most exciting fields in nuclear physics.

• Lots of data have been accumulated, e.g.,– Hadrons: freeze-out status– Hyperons: enhancement of multi-strange baryons– Leptons: in-medium effect, J/Psi suppression

• We need a systematic approach as a function of beam energy and system size.

• Active research is and will be required at least for the next two decades with LHC and SIS200.

present and future perspectives of relativistic heavy-ion collisions 고려대학교 홍 병 식

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