RHIC: Physics Results

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RHIC Physics Results
Gunther Roland
IV International Symposium on LHC Physics and
Detectors Fermilab 5/1-5/3 2003
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Exploring QCD with Heavy Ions
I
II
III
IV
Early Universe
II
Temperature (MeV)
Quark-Gluon Plasma

1. Structure of Relativistic Nuclei
2. Mechanism of Entropy Production
3. QCD phase diagram
4. Properties of QGP

I
III
200
Critical Point
IV
Phase Boundary
Hadron Gas
Atomic Nuclei
0
0
1
Matter Density mB (GeV)
3
Interlude Collision Geometry
Spectators
Participant Region
b
2R 15fm
Spectators
Smaller Impact Parameter b
More Participants (Npart)
Bigger Collision System
More Produced Particles!
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Relativistic Heavy Ion Collider

• First Physics in 00
• Versatile machine
• AuAu (00-02)
• 19.6 GeV
• 56 GeV
• 130 GeV
• 200 GeV
• pp (02,03)
• 200 GeV polarized
• dAu (03)
• 200 GeV

• 4 Experiments
• 2 big
• 2 small
• Complementary capabilities

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STAR

• Large acceptance tracking detector
• Mass, charge and momentum for gt1000 hadrons per
  event

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PHENIX

• High Rate, Particle ID, Triggering
• Rare particles Leptons, High pT

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PHOBOS

• Full Acceptance Multiplicity Detector
• High precision spectrometer near y0 (low pT)

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BRAHMS

• Particle Production at small angles
• High resolution spectrometer good particle ID

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• Bulk Particle Production _at_ RHIC
• Initial Conditions/Energy Density
• Thermalization
• Hadro-Chemistry
• Expansion Dynamics

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4-p Multiplicity at RHIC
BRAHMS PLB 523 (2001) 227, PRL 88 (2002) 202301
BRAHMS
130 GeV
BRAHMS
200 GeV
dN/dh
Nice agreement!
PHOBOS nucl-ex/0210015
200 GeV
19.6 GeV
130 GeV
PHOBOS
PHOBOS
PHOBOS
dN/dh
Pseudo-rapidity
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Energy Density
W. Busza, Moriond 03
Density of Particles Produced at y0
Total energy released 2000GeV
Max. initial overlap volume
Initially released energy density 5GeV/fm3
Note energy density inside proton 0. 5GeV/fm3
Energy of Collision
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Azimuthal Anisotropy
Head on view of colliding nuclei
Peripheral
Central
Initial State Anisotropy Coordinate Space
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Anisotropy v2 vs Centrality
STAR
? lt 1.3 0.1 lt pt lt 2.0
PHENIX
Consistent results Hydro-limit reached for
mid-central collisions
from R. Snellings
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• Bulk Particle Production _at_ RHIC
• Initial Conditions/Energy Density gt 5 GeV/fm3
• Thermalization
• Hadro-Chemistry
• Expansion Dynamics

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Charged Particle Spectra
Th. Ullrich QM02
Results (largely) consistent Clear Mass Hierarchy
of Slopes
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Multi-Strange Particles
J. Castillo SQM03
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Statistical Model Fit
Relative Abundance Two Parameters !
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• Bulk Particle Production _at_ RHIC
• Initial Conditions/Energy Density gt 5 GeV/fm3
• Thermalization
• Hadro-Chemistry Tch 180 MeV, mB25MeV
• Expansion Dynamics

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Hydro Fits to Spectra
Simultaneous Fit to p,k,p gives Kinetic
Freeze-Out Temperature, Transverse Expansion
velocity
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Hydro Fit to Correlation Data
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
Fabrice Retiere SQM 03, Mike Lisa
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• Bulk Particle Production _at_ RHIC
• Initial Conditions/Energy Density gt 5 GeV/fm3
• Thermalization
• Hadrochemistry Tch 180 MeV, mB25MeV
• Expansion Dynamics Tth 110 MeV, ltbTgt 0.6c
• lttfogt 10 fm/c, Dtfo 0-3 fm/c

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• Bulk Particle Production _at_ RHIC
• Initial Conditions/Energy Density gt 5 GeV/fm3
• Thermalization
• Hadrochemistry Tch 180 MeV, mB25MeV
• Expansion Dynamics Tth 110 MeV, ltbTgt 0.6c
• lttfogt 10 fm/c, Dtfo 0-3 fm/c

Consistent Description of Final State But were
missing a picture of Dynamical Evolution
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• II. Dense Matter Diagnostics _at_ RHIC
• Jets
• Virtual and Real Photons
• Quarkonia

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Dense Matter Diagnostics
Study fate of jets in dense matter in AuAu
Jet cross-section calculable in QCD
Leading Particle
Leading Particle
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STAR AuAu
Opal ee-
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Dense Matter Diagnostics
Study fate of jets in dense matter in AuAu
Jet cross-section calculable in QCD
Leading Particle
Leading Particle
Poor mans jet Leading Particles
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Jet Quenching at High pT
expected
protonproton
observed
AuAu
Yield at high pT in AA is 6 times smaller than
expected
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Jets in Dense Matter
Leading Particle

• 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

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Peripheral AuAu data
D. Hardtke QM 02

• Jets seen in peripheral AuAu and pp
• Azimuthal correlations
• Small angle (Df 0)
• Back-to-Back (Df p)

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Central AuAu data
D. Hardtke QM 02

• Disappearance of back-to-back correlations in
  central AuAu
• Away-side particles absorbed or scattered in
  medium

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Instant Thermalization
E. Shuryak, nucl-th/0112042
Peripheral
Limit (lmfp 0)
High pT particles produced early Biggest
anisotropy
Central
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Thermalization timescale
time
t0

• To fully preserve anisotropy
• Instant formation of dense system (lmfp small)
• Why instant? Once washed out, anisotropy cant
  be recovered!

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Anisotropy in Parton Cascade
HIJING x 80 HIJING x 35 HIJING x 13 HIJING x
1 hydro , sBC
0.1
Anisotropy
0.06
Molnar, Gyulassy
0.02
Parton cascade can describe data if
cross-sections are multiplied by 13!
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Proton puzzle
?
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Understanding low vs high pT
Fries, Mueller, Nonaka,Bass nucl-th/0301087
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III. RHIC in Context
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Total Multiplicity vs. Beam Energy
PHOBOS QM02, Steinberg
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Chemistry vs sqrt(s)
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Asymptotic region at RHIC?
Universality? Energy Hadrons
ee-
What about strangeness?
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Mid-Rapidity K/?
NA49 (V. Friese SQM03)
Non-monotonic Evolution! Oeschler et al
Thresholds vs Baryo-chemical potential
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Kaon Slope Parameters
NA49 (V. Friese SQM03)
PHENIX
PHENIX
NA49
NA49
AGS
AGS
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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?