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Mark D. Baker
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/
Mark D. Baker
Some of the people
Mark D. Baker
Where they come from • BNL
– Chemistry, Collider-Accelerator, Physics
• >1000 people from around the world– Brazil, Canada, China, Croatia, Denmark, France,
Germany, India, Israel, Japan, Korea, Norway, Poland, Russia, Sweden, Taiwan, UK, US
Mark D. Baker
What is the universe made of?&
What holds it together?
Mark D. Baker
What is the universe made of?
Placeholder
Mark D. Baker
What holds it together?:The Fundamental Forces
Mark D. Baker
Let’s smash some atoms!
+ -
-
u
u u u u u
d
u d u du du d
proton
proton
pion ()
uud
Mark D. Baker
If you can’t smash it, heat it!
Temperature
Plasma
+
---
-+
Pressure
Mark D. Baker
Sideways slide - How much heat?
Placeholder
Mark D. Baker
Heat is also a window back in time
Mark D. Baker
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
Mark D. Baker
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
Mark D. Baker
Where?
Mark D. Baker
Inside the tunnel
Mark D. Baker
STARSTAR
Mark D. Baker
RHIC Computing Facility
The detectors can take 7 Gigabytes of data / minute!
Mark D. Baker
First Collisions
Mark D. Baker
Timeline
CollisionsDelivered
Star & Phobos
Brahms & Phenix
|-----June------|-----July------|----August----|--September--|---October---|---November--| 2000
sNN = 130 GeV
Au-Au
|-December--|--January---|--February--|----March----|-----April-----|
(PHOBOS)
(STAR) (PHENIX)
1st Collisions
Papers (PHENIX)(BRAHMS)(PHOBOS)
(STAR)
Title:
Creator:qcdisplay2.2 Contact [email protected]:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.
Papers
Mark D. Baker
Looking for collective effects...
Is Gold+Gold > 197 * Proton+Proton?
Mark D. Baker
AuAu @ RHIC is something new!
PHOBOS
CERN/SPS
Energy/nucleon (GeV)
Produced Particles/Participating Nucleon Pair
ppPHENIX
BRAHMSprelim.
PRL 85 (2000) 3100
Mark D. Baker
How many produced particles?
Measured # in ahead-on collision:
4100±410
(Simulation)
PHOBOS Preliminary
Mark D. Baker
Elliptic Flow: A collective effect
dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R)) + ... )
Elliptic flow
Beam’s eye view of anon-central collision:
Asymmetric particle distribution:
Particles prefer to be “in-
plane”
Mark D. Baker
Elliptic Flow Expectations
Hydrodynamic model
V2
Normalized Multiplicity
midrapidity : || < 1.0
Preliminary
Particle asymmetry
No collective motion
Hydrodynamic “Flow”
Mark D. Baker
Elliptic Flow
Hydrodynamic model
V2
Normalized Multiplicity
midrapidity : || < 1.0
Preliminary
PRL 86 (2001) 402Particle asymmetry
Mark D. Baker
Collective motion largest at RHIC
STAR, PRL 86 (2001) 402
Mark D. Baker
It even makes sense in detail
Huovinen, Kolb, Heinz
Particle asymmetry
Mark D. Baker
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
Mark D. Baker
We see the conditions at freezeout(a lower limit to the maximum Temperature)
FreezeoutHottest period
RT
1
Expansion cooling
Mark D. Baker
Separating Temperature & Expansion
2
2
22
3
c
vmT
N
E
Compare produced particles with different masses!
2
2
. 3c
vmTTeff
Effective Temperature
mass
Mark D. Baker
1.7 1012 oK
RHIC shows rapid expansion& a high temperature
!3
2
c
vEffectiveTemperature(GeV)
CERN NA49
STAR Preliminary
Mark D. Baker
Another thermometer
In an equilibrium system, twoparameters are sufficient to predict the “chemical” mix:
(# pions) / (# protons)(# kaons) / (# pions)(# anti-protons)/(# protons) et cetera.
Temperature (T)and “net amount of matter” (B)
Mark D. Baker
Temperature from particle ratios
T = (2.2+0.2) 1012 oK-
STAR Preliminary
23
64
1,5,7
)/( 1. hhK
pp / 2.
KK / 4.
/ 3.
hK / 5. *0
/ 6./ 7. p
Mark D. Baker
Temperature at Freezeout
• Chemical: T = (2.2+0.2) 1012 oK• Kinetic: T = (1.7+0.4) 1012 oK
• We did reach ~ 2 trillion K!
--
Mark D. Baker
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.
Mark D. Baker
What happens before freeze-out?•Energetic particles come from quark or gluon “jets”.•They interact with the dense medium, but can’t thermalize.•Jet energy loss (“quenching”) is predicted.•Jet quenching measures the density early in the collision.
pion
Mark D. Baker
Jet quenching at RHIC?
Neutral pionsCentral collisions
No quenching
Number
Transverse Momentum (GeV/c)
Neutral pions Peripheral collisions
Quenching
Transverse Momentum (GeV/c)
Preliminary
Mark D. Baker
More on jet quenching
Details need to be understood before conclusions can be drawn.
Mark D. Baker
Summary
• We’ve 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.
Mark D. Baker
Outlook
• More analysis• More data (x100 next run)
– Allows new early time probes
• More variety of data– Energy and species scan
• Detector Upgrades
It’s going to get even better!
Stay tuned for news about the strong force!