Mark D. Baker
Some Like it REALLYREALLY Hot!Studying Matter Under Extreme Conditions
Mark D. BakerChemistry Department
Brookhaven National Laboratory
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
neutron
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
Hot and Dense Laboratory MatterTry # 1: Diamond Anvil
Achieved Our Goal
T 2000 K 2 1012 K
p 106 atm 5x1021 atm
r ~10 mm
t hours
Mark D. Baker
Hot and Dense Laboratory MatterTry # 2: X-pinch plasma
Achieved Our Goal
T 107 K 2 1012 K
p ? 5x1021 atm
r 10 m
t 1 ns
Mark D. Baker
Hot and Dense Laboratory MatterTry # 3: Free Electron Laser
Planned Our Goal
T 108 K 2 1012 K
p ? 5x1021 atm
~ 0.1 nm planned (6 nm achieved)
XFEL, Tellerhoop, Germany
Mark D. Baker
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
Hot and Dense Laboratory MatterTry # 4: Heavy Ion Collisions
2x1012 K, 5x1021 atm
Mark D. Baker
RHIC...
Mark D. Baker
ARGONNE NATIONAL LABORATORY
BROOKHAVEN NATIONAL LABORATORY
INSTITUTE OF NUCLEAR PHYSICS, KRAKOW
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
NATIONAL CENTRAL UNIVERSITY, TAIWAN
UNIVERSITY OF ROCHESTER
UNIVERSITY OF ILLINOIS AT CHICAGO
UNIVERSITY OF MARYLAND
Birger Back, Alan Wuosmaa
Mark Baker, Donald Barton, Alan Carroll, Nigel George, Stephen Gushue, George Heintzelman, Burt Holzman, Robert Pak, Louis Remsberg, Peter Steinberg, Andrei Sukhanov
Andrzej Budzanowski, Roman Holynski, Jerzy Michalowski, Andrzej Olszewski, Pawel Sawicki , Marek Stodulski, Adam Trzupek, Barbara Wosiek, Krzysztof Wozniak
Wit Busza (Spokesperson), Patrick Decowski, Kristjan Gulbrandsen, Conor Henderson, Jay Kane , Judith Katzy, Piotr Kulinich, Johannes Muelmenstaedt, Heinz Pernegger, Corey Reed, Christof Roland, Gunther Roland, Leslie Rosenberg, Pradeep Sarin, Stephen Steadman, George Stephans, Gerrit van Nieuwenhuizen, Carla Vale, Robin Verdier, Bernard Wadsworth, Bolek Wyslouch Chia Ming Kuo, Willis Lin, Jaw-Luen Tang
Joshua Hamblen , Erik Johnson, Nazim Khan, Steven Manly,Inkyu Park, Wojtek Skulski, Ray Teng, Frank Wolfs
Russell Betts, Edmundo Garcia, Clive Halliwell, David Hofman, Richard Hollis, Aneta Iordanova, Wojtek Kucewicz, Don McLeod, Rachid Nouicer, Michael Reuter, Joe Sagerer
Richard Bindel, Alice Mignerey
The PHOBOS Collaboration
Mark D. Baker
135,000 Silicon Pad channels
PHOBOS Apparatus
12 meters of Beryllium beampipe
Mark D. Baker
Ring Counter
Octagon Detector
Vertex Detector
PHOBOS Silicon Detector
Octagon Detector: 2.7 x 8.8 mm2
Vertex Detector: 0.4 x 12 mm2
Mark D. Baker
RHIC Computing Facility
PHOBOS writes ~ 1 Gigabyte of data / minute!
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– Quantum ChromoDynamics– Confinement
Mark D. Baker
How many produced particles?
Measured # of charged particles in ahead-on collision:
4100±210 @ 130 GeV
5055±250 @ 200 GeV0 +3-3 +5.5-5.5
simulation
Mark D. Baker
Multiplicity at mid-rapidityModels in 1999
Models: NPA 698, (2002) 78c,299c
PRL 88 (2002) 022302
Models in 2000
Mark D. Baker• Data favors models with minimal entropy production
Energy Dependence
Soft
Hard
PRL 88 (2002) 022302
90% C.L. band
Mark D. Baker
Implications:• The initial state is dominated by soft physics• Limited entropy production in late stages.
Colliding Nuclei HardCollisions
Parton Cascade
Hadron Gas & Freeze-out
1 2 3 4
Geometry/Saturation QGP? / Fragmentation Gentle Freeze-out
QCD
Mark D. Baker
Many ways to slice pz
FTTz xs
pymp2
sinhsinh:
Away from mid-rapidity:
epem Ty
T TT pmy ln
Rapidity: Generalized velocity
Pseudorapidity: ~y: easier to measure
Feynman x: scaled pz
Mark D. Baker
dN/d
dN/d
dN/d
dN
/d
dN/d
dN/d
200 GeV130 GeV
Central
Peripheral
Typical Systematic Errors
Latest PHOBOS results
Mark D. Baker
Naïve expectation (boost-invariance)
y y
Increasing E
y’=y-ybeam
0
dN/dy’Fragmentation Region
Mark D. Baker
Results : Limiting Fragmentation
Systematic errors not shown
PHOBOS results in “target frame”
PHOBOS 200 0-6%PHOBOS 130 0-6%EMU-13 17 0-9.4% (different frame)
Limit curve; extent grows with energy
SPS data (20 GeVRHIC coming soon)
Mark D. Baker
Can we see the “Limit Curves”?
p + p inel.
UA5, Z.Phys.C33, 1 (1986)
Line “p”to guide the eye
Au+Au
Systematic errors not included
1.45 x line “p”
Systematic errors not shown
Mark D. Baker
Elliptic Flow: A collective effect
Hydrodynamic modelV2
Normalized Multiplicity
midrapidity : || < 1.0
Preliminary
No collective motion
Hydrodynamic “Flow”
dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R)) + ... )
Mark D. Baker
Elliptic Flow
Hydrodynamic model
V2
Normalized Multiplicity
midrapidity : || < 1.0
Preliminary
Particle asymmetry
Mark D. Baker
v2
Flow also non-boost-invariant
v2: quantifies elliptical anisotropy
Azimuthal shape changes as strong function of
Consistent withlarge suggestedby saturation(and required bysome hydro models)
Averaged over centrality PHOBOS Preliminary
Errors are statistical only (systematic errors ~ 0.007)
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– Quantum ChromoDynamics
– 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
1.7 1012 oK
RHIC shows rapid expansion& a high temperature
!3
2
c
vEffectiveTemperature(GeV)
CERN NA49
STAR Preliminary
2
2
. 3c
vmTTeff
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
Particle Ratios tell us about final state
Braun-Munzinger et. al., Phys. Lett. B 518 (2001) 41
T = 176 MeVB = 46 MeV
Statistical modelsconsistent withparticle ratio data:simple filling of phasespace?
Suggest thermalizationat T ~ Tc, nonzeronet baryon density(SPS value: B = 270 MeV) 65 + 65 GeV beam energy
Mark D. Baker
Temperature at Freezeout
• Temperature in MeV units
– Chemical: T = (170 ± 20) MeV
– Kinetic: T = (150 ± 40) MeV
• Temperature in oK (1eV = 11,600 K)
– Chemical: T = (2.0 ± 0.2) 1012 oK
– Kinetic: T = (1.7 ± 0.3) 1012 oK
• We did reach ~ 2 trillion K!
Mark D. Baker
Fully reversiblemagnetic field
Particle ratios at 100+100 GeV!
p
K+
+
Positive
Charge
Negative
Charge
K-
p
-
Tru
ncat
ed <
dE/d
x> [
MIP
]
)(03.0)(02.074.0
)(04.0)(03.095.0
)(020.0)(006.0025.1
sysstatp
p
sysstatK
K
sysstat
Preliminary
Mark D. Baker
Excitation function of B
Nucl. Phy. A697: 902-912 (2002)
Extrapolation of fit
Mark D. Baker
Energy Density Estimate (Bj)
Latticec
Bj~ 5 GeV/fm3
Bj~ 25 GeV/fm3
02j
TB
1 1 d
c dy
E
R
formation time: 0.2 - 1 fm
PRL 87 (2001) 052301
Mark D. Baker
If you just believe the lattice...
CERN SPS (s = 17 GeV) i ~ 3-10 GeV/fm3
Ti ~ 220-290 MeV
BNL RHIC (s = 200 GeV) i ~ 5-25 GeV/fm3 Ti ~ 250-350 MeV
TT
Karsch et al.
Mark D. Baker
Putting it all together
• Universal curve!• RHIC:
– “bulk” matter
– high energy density
initial ~ 5-25 GeV/fm3
(lattice Ti >250 MeV)
– freezeout near TC
– early collective expansionvt ~ 0.65 c
quark gluonplasma
SIS
AGS
SPS
RHIC
hadron gas
Tem
per
atur
e (M
eV)
50
200
150
100
250
350
300
400
Baryonic chemical potential B (GeV)0.2 0.4 0.6 0.8 1 1.2 1.4
LEP!
Mark D. Baker
Summary so far
• We’ve learned a lot about the system– The system is behaving collectively.– We have reached 2-4 trillion degrees K.– The system is expanding rapidly.
• AA may illuminate QCD “directly”– Low Nch: soft initial state effects dominate
• Thermal partons?
– The source is not boost invariant• dN/d limit curve from QCD and GAu(x)
Mark D. Baker
PHOBOS Future I (analysis)
Quantum MechanicalSource imaging (HBT)
Mark D. Baker
Plan of attack - where do we go?
• Collide gold nuclei at high energy– Collider, detectors, computers
• Understand the collision dynamics– Collective motion, equilibrium– Temperature, density
• Learn about the strong interaction– Quantum ChromoDynamics– Confinement
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
Failure to scale! (jet quenching?)
Details need to be understood before conclusions can be drawn.
Mark D. Baker
PHOBOS Future II
I. Faster!!
Upgrade DAQ from40 Hz to 500-700 Hz
Upgrade triggering
II. Better particle IDMove TOF wall+...
Compare high Pt behavior of: pp, dA, AA(as well as soft behavior)
R.Pak
Sukhanov
Mark D. Baker
PHOBOS future III (analysis)Lower pT at pp midrapidity
ISR data is inelastic
Universality?
Mark D. Baker
Brookhaven Future (!): eRHIC
•Directly probe dense strongly interacting matter.• Nonabelian QCD effects in the low x nuclear structure function...
Mark D. Baker
Conclusion
• We’ve accomplished a lot already– Detector, physics, papers.
• RHIC should illuminate QCD “directly”– dN/d limit curve from QCD and GAu(x)
– Universality of “fragmentation”– “Jet quenching” or new scaling law– Something we haven’t thought of yet...
• Physics on the distant horizon– eRHIC - probing QCD in a different way.
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