rhic: physics results

Gunther Roland/MIT LHC 2003

RHIC: Physics Results

Gunther Roland

IV International Symposium on LHC Physics and Detectors

Fermilab 5/1-5/3 2003


Exploring QCD with Heavy Ions

Matter Density B (GeV)

I II III IV

Tem

per

atu

re (

MeV

)

Quark-Gluon Plasma

Hadron Gas

Phase Boundary

Early Universe

0

200

0

Atomic Nuclei

1

Critical Point

I

II

III

IV

1. Structure of Relativistic Nuclei

2. Mechanism of Entropy Production

3. QCD phase diagram

4. Properties of QGP


Interlude: Collision Geometry

b2R ~ 15fm

Spectators

Spectators

Participant Region

Smaller Impact Parameter b

Bigger Collision System

More Participants (Npart)

More Produced Particles!


Relativistic Heavy Ion Collider

First Physics in ‘00

Versatile machine – Au+Au (‘00-’02)

• 19.6 GeV

• 56 GeV

• 130 GeV

• 200 GeV

– p+p (‘02,’03)• 200 GeV

polarized

– d+Au (‘03)• 200 GeV• 4 Experiments

– 2 big– 2 small

• Complementary capabilities


STAR

• Large acceptance tracking detector• Mass, charge and momentum for >1000 hadrons

per event


PHENIX

• High Rate, Particle ID, Triggering

• Rare particles: Leptons, High pT


PHOBOS

• Full Acceptance Multiplicity Detector• High precision spectrometer near y=0 (low pT)


BRAHMS

• Particle Production at small angles

• High resolution spectrometer & good particle ID


Bulk Particle Production @ RHIC

1. Initial Conditions/Energy Density

2. Thermalization

3. Hadro-Chemistry

4. Expansion Dynamics


4- Multiplicity at RHICd

N/d

Pseudo-rapidity

19.6 GeV 130 GeV 200 GeVPHOBOS PHOBOS PHOBOS

BRAHMS 130 GeV BRAHMS 200 GeV

dN

/d

Nice agreement!

PHOBOS nucl-ex/0210015

BRAHMS PLB 523 (2001) 227, PRL 88 (2002) 202301


Initially released energy density

~ 5GeV/fm3

Note: energy density inside proton ≈ 0. 5GeV/fm3

1=1−=

o45

1000~all

d

dN⎟⎟⎠

⎞⎜⎜⎝

⎛

GeVE 1~

32 200~)1(~ fmfmR

Total energy released ~2000GeVMax. initial overlap volume

Den

s ity

o

f P

arti

c le s

Pro

du

c ed

at

y=0

Energy of Collision

Energy DensityW. Busza, Moriond ‘03


Azimuthal Anisotropy

“Head on” view of colliding nuclei

Peripheral

Central

Initial State AnisotropyCoordinate Space

Final State AnisotropyMomentum Space

Interaction!

2*v2

Azimuthal Angle (rad)


Anisotropy v2 vs Centrality

STAR

|| < 1.3

0.1 < pt < 2.0

PHOBOS

PHENIX

from R. Snellings

Consistent results

Hydro-limit reached for

mid-central collisions



1. Initial Conditions/Energy Density: > 5 GeV/fm3

2. Thermalization:

3. Hadro-Chemistry



Charged Particle Spectra

Results (largely) consistent

Clear Mass Hierarchy of Slopes

Th. Ullrich QM’02


Multi-Strange Particles

STAR Preliminary

J. Castillo SQM’03


Statistical Model Fit

Relative Abundance: Two Parameters !




2. Thermalization:

3. Hadro-Chemistry: Tch ~ 180 MeV, B~25MeV



‘Hydro’ Fits to Spectra

Simultaneous Fit to ,k,p gives

Kinetic Freeze-Out Temperature,

Transverse Expansion velocity


‘Hydro’ Fit to Correlation Data

Fabrice Retiere SQM ‘03, Mike Lisa

Consistent Data from

STAR, PHENIX, PHOBOS

Also

HBT vs reaction plane

Unlike particles

Balance Functions

Short-lived Resonances

Consistent Results

Lifetime ~ 10 fm/c

Particle emission over

few fm/c




2. Thermalization:

3. Hadrochemistry: Tch ~ 180 MeV, B~25MeV

4. Expansion Dynamics: Tth ~ 110 MeV, <T> ~ 0.6c

<fo>~ 10 fm/c, fo~ 0-3

fm/c




2. Thermalization:

3. Hadrochemistry: Tch ~ 180 MeV, B~25MeV

4. Expansion Dynamics: Tth ~ 110 MeV, <T> ~ 0.6c

<fo>~ 10 fm/c, fo~ 0-3

fm/c Consistent Description of Final State

But we’re missing a picture of Dynamical Evolution


II. Dense Matter Diagnostics @ RHIC

1. Jets

2. Virtual and Real Photons

3. Quarkonia


Dense Matter Diagnostics

Leading Particle

Hadrons

q

q

Hadrons

Leading Particle

Hadrons

q

q

Hadrons

Leading Particle

Jet cross-section calculable in QCD

Study fate of jets in dense matter in Au+Au

Leading Particle


STAR Au+AuOpal e+e-


Dense Matter Diagnostics

Leading Particle

Hadrons

q

q

Hadrons

Leading Particle

Hadrons

q

q

Hadrons

Leading Particle

Jet cross-section calculable in QCD

Study fate of jets in dense matter in Au+Au

Poor man’s jet: Leading Particles

Leading Particle


“Jet Quenching” at High pT

Yield at high pT in AA is 6 times smaller than expected

expected

observedproton+proton

Au+Au


Jets in Dense Matter

Are we really looking at jets?• Look for jet structure by

measuring– small angle correlations– back-to-back

correlations

relative to high pT leading particle

Hadrons

q

q

Hadrons

Leading Particle

Leading Particle


Peripheral Au+Au data

• Jets seen in peripheral Au+Au and p+p• Azimuthal correlations

– Small angle ( ~ 0)– Back-to-Back ( ~ p)

D. Hardtke

QM ‘02


Central Au+Au data

• Disappearance of back-to-back correlations in central Au+Au

• Away-side particles absorbed or scattered in medium

D. Hardtke

QM ‘02


“Instant” ThermalizationE. Shuryak, nucl-th/0112042

STAR

Central

Peripheral

High pT particlesproduced early:Biggest anisotropy

Limit (mfp = 0)


Thermalization timescale

• To fully preserve anisotropy:– Instant formation of dense system (mfp small)

• Why “instant”? Once washed out, anisotropy can’t be recovered!

timet=0


Anisotropy in Parton Cascade

HIJING x 80HIJING x 35HIJING x 13HIJING x 1hydro , sBC

Peripheral Central

0.06

0.1

0.02

An

iso

tro

py

Parton cascade can describe data…

…if cross-sections are multiplied by 13!

Molnar, Gyulassy


“Proton puzzle”

?


Understanding low vs high pT

Fries, Mueller, Nonaka,Bass nucl-th/0301087


III. RHIC in Context


(Mueller 1983)

)/exp( sAsch BN αα∝

Total Multiplicity vs. Beam EnergyPHOBOS QM’02, Steinberg

pp/pp

A+A

e+e-

Central A+A

<N

ch>

/e+e- F

it


Chemistry vs sqrt(s)Nucl. Phy. A697: 902-912 (2002)


Asymptotic region at RHIC?

pp/pp

A+A

e+e-Universality?

Energy

Hadronse+e-

What about strangeness?


Mid-Rapidity K/

Non-monotonic Evolution!

Oeschler et al: Thresholds vs Baryo-chemical potential

NA49 (V. Friese SQM’03)


Kaon Slope Parameters

NA49 (V. Friese SQM’03)

NA49NA49

AGS AGS

PHENIXPHENIX


Summary

• Extensive and Consistent Data Sets– BRAHMS, PHENIX, PHOBOS, STAR– AGS, SPS, RHIC

• Consistent and Concise description of Final State – Bulk particle production

– Intermediate pT spectra + correlations

• Challenge: Consistent Dynamical Scenario– What makes all this happen in 10fm/c?

rhic: physics results

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