What have we learned from RHIC Mark D' Baker Chemistry Department

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What have we learned from RHIC?Mark D.
BakerChemistry Department
Thanks to W. Busza, Axel
Drees, J. Katzy, B. Lugo, P. Steinberg, N. Xu, F.
Wolfs BSA Lecture Committee Particle Data
Group http//ParticleAdventure.org/
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Some of the people
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Where they come from

• BNL
• Chemistry, Collider-Accelerator, Physics
• gt1000 people from around the world
• Brazil, Canada, China, Croatia, Denmark, France,
  Germany, India, Israel, Japan, Korea, Norway,
  Poland, Russia, Sweden, Taiwan, UK, US

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What is the universe made of?What holds it
together?
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What is the universe made of?
Placeholder
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What holds it together?The Fundamental Forces
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Lets smash some atoms!
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proton
u
d
u
d
proton
u
d
u
d
u
d
u
d
u
u
u
u
u
u
pion (p)
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If you cant smash it, heat it!
Pressure
Plasma
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Temperature
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Sideways slide - How much heat?
Placeholder
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Heat is also a window back in time
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How do we get to 2 trillion oK?
Collide Gold nuclei at 99.99 of the speed of
light
But Will these fast violent collisions
teach us anything?
10-23 seconds, 10-38 liters
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The plan of attack

• Collide gold nuclei at high energy
• Collider, detectors, computers
• Understand the collision dynamics
• Collective motion, equilibrium
• Temperature, density
• Learn about the strong interaction
• Quark-Gluon Plasma
• Confinement

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Where?
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Inside the tunnel
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RHIC Computing Facility
The detectors can take 7 Gigabytes of data /
minute!
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First Collisions
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Timeline
?sNN 130 GeV Au-Au
Brahms Phenix
Collisions Delivered
Star Phobos
1st Collisions
-----June-----------July----------August------
September-----October------November--
2000
(PHOBOS)
(STAR)
Papers (PHENIX) (BRAHMS)(PHOBOS)
Papers
-December----January-----February------March--
-------April-----
(STAR) (PHENIX)
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Looking for collective effects...
Is GoldGold gt 197 ProtonProton?
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AuAu _at_ RHIC is something new!
PRL 85 (2000) 3100
Produced Particles/ Participating Nucleon Pair
PHENIX
PHOBOS
BRAHMS prelim.
CERN/SPS
Energy/nucleon (GeV)
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How many produced particles?
Measured in a head-on collision 4100410
PHOBOS Preliminary
(Simulation)
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Elliptic Flow A collective effect
Beams eye view of a non-central collision
Asymmetric particle distribution
f
Particles prefer to be in-plane
dN/d(f -YR ) N0 (1 2V1cos (f-YR) 2V2cos
(2(f-YR)) ... )
Elliptic flow
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Elliptic Flow Expectations
Particle asymmetry
midrapidity h lt 1.0
V2
Hydrodynamic model
Hydrodynamic Flow
Preliminary
No collective motion
Normalized Multiplicity
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Elliptic Flow
PRL 86 (2001) 402
Particle asymmetry
midrapidity h lt 1.0
V2
Hydrodynamic model
Preliminary
Normalized Multiplicity
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Collective motion largest at RHIC
STAR, PRL 86 (2001) 402
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It even makes sense in detail
Particle asymmetry
Huovinen, Kolb, Heinz
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Plan of attack - where are we?

• Collide gold nuclei at high energy
• Collider, detectors, computers
• Understand the collision dynamics
• Collective motion, equilibrium
• Temperature, density
• Learn about the strong interaction
• Quark-Gluon Plasma
• Confinement

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We see the conditions at freezeout (a lower limit
to the maximum Temperature)
Freezeout
Hottest period
Expansion cooling
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Separating Temperature Expansion
Effective Temperature
mass
Compare produced particles with different masses!
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RHIC shows rapid expansion a high temperature
Effective Temperature (GeV)
STAR Preliminary
CERN NA49
1.7 1012 oK
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Another thermometer
In an equilibrium system, two parameters are
sufficient to predict the chemical mix (
pions) / ( protons) ( kaons) / ( pions) (
anti-protons)/( protons) et cetera.
Temperature (T) and net amount of matter (mB)
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Temperature from particle ratios
STAR Preliminary
T (2.20.2) 1012 oK
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4
6
3
2
1,5,7
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Temperature at Freezeout

• Chemical T (2.20.2) 1012 oK
• Kinetic T (1.70.4) 1012 oK
• We did reach 2 trillion K!

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The yields are compared to predictions by
Hijing. The SPS data values from NA44, NA49 are
plotted as reference. The ?3 measurement
converted to y using the accepted mean pt.
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What happens before freeze-out?

• Energetic particles come from quark or gluon
  jets.
• They interact with the dense medium, but cant
  thermalize.
• Jet energy loss (quenching) is predicted.
• Jet quenching measures the density early in the
  collision.

pion
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Jet quenching at RHIC?
Preliminary
Number
Neutral pions Peripheral collisions
Neutral pions Central collisions
No quenching
Quenching
Transverse Momentum (GeV/c)
Transverse Momentum (GeV/c)
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More on jet quenching
Details need to be understood before conclusions
can be drawn.
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Summary

• Weve learned a lot about the system
• We have reached 2 trillion degrees K
• The system is expanding rapidly.
• It was probably even hotter and denser
• Possible first evidence of jet quenching!
• Should lead to a measure of the density
• No conclusions yet about the strong force.

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Outlook
Its going to get even better!

• More analysis
• More data (x100 next run)
• Allows new early time probes
• More variety of data
• Energy and species scan
• Detector Upgrades

Stay tuned for news about the strong force!