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PHENIX OVERVIEW
W.A. Zajc
Columbia University
for the PHENIX Collaboration
Special thanks to J. Mitchell (BNL) for animations
2
OutlineOutline
Why Nuclear Physics?
Why RHIC?
Why PHENIX?
Where do we go from here?
3
Central Truths of Nuclear Physics
Central Truths of Nuclear Physics
We are nothing
We are dust
We don’t matter
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We are nothing (c. 1900)
We are nothing (c. 1900)
Most of “us” is (nearly) empty space 99.9% of the mass of atoms is
contained in the nucleus The nucleus is about one-trillionth
( 1/1,000,000,000,000 ) the size of the atom
ProtonProtonNeutronNeutronQuarksQuarksHeld togetherHeld togetherby gluonsby gluons(not shown)(not shown)
NucleusNucleus(“ion” when alone)(“ion” when alone)
AtomAtom
KeyKey
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We are dust (c. 1950)
We are dust (c. 1950)
Only the lightest elements (Hydrogen and Helium) were created in the Big Bang
The rest of “us” is stardust All heavy elements (like the Carbon and
Nitrogen we’re made of) were “cooked” together inside stars
Explosions of those (early) stars spread the heavier elements throughout the universe.
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We don’t matter (c. 2000)
We don’t matter (c. 2000)
More accurately: We’re not matter
Recall nearly all the mass of each atom is concentrated in the nucleus: Each nucleus consists of
neutrons and protons Each neutron and proton consists
of 3 quarks Each quark has the mass of about
1% of a proton or neutron(!) The rest of the mass of protons
and neutrons (and hence our mass) is “frozen energy” from the Big Bang
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Phase Transitions
Phase Transitions
The “great freeze” took place about 10 millionths of a second after the Big Bang
General name for such phenomena: Phase transitionExamples:
Steam to water to ice
(Free quarks and gluons) to (protons and neutrons) to (??)
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Phase DiagramsPhase Diagrams
Water
Nuclear Matter
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A Silly AnalogyA Silly Analogy Suppose…
You lived in a frozen world where water existed only as ice and ice comes in only quantized sizes ~ ice cubes and theoretical friends tell you there should be a liquid phase and your only way to heat the ice is by colliding two ice cubes So you form a “bunch” containing a billion ice cubes which you collide with another such bunch 10 million times per second which produces about 1000 IceCube-IceCube collisions per
second which you observe from the vicinity of Mars
Change the length scale by about 10 trillion You’re doing physics at RHIC!
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Boiling Neutrons and Protons
Boiling Neutrons and Protons
Fundamental Method:Collide heavy nuclei at the highest
possible energies:
Fundamental Goals: Create (new) dense forms of matter Re-create the quark-gluon phase transition
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In PicturesIn Pictures
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RHIC = Relativistic Heavy Ion Collider Located at Brookhaven National Laboratory
RHICRHIC
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RHIC’s Experiments
RHIC’s Experiments
STAR
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How is RHIC Different?
How is RHIC Different?
It’s a collider Detector systematics independent of ECM (No thick targets!)
It’s dedicated Heavy ions will run 20-30 weeks/year
It’s high energy Access to non-perturbative phenomena
Jets Non-linear dE/dx
Its detectors are comprehensive ~All final state species measured with a
suite of detectors that nonetheless have significant overlap for comparisons
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What is PHENIX?What is PHENIX? Pioneering High Energy Nuclear Interaction
eXperiment Goals:
Broadest possible study of A-A, p-A, p-p collisions to Study nuclear matter under extreme conditions Using a wide variety of probes sensitive to all
timescales Study systematic variations with species and
energy Measure spin structure of the nucleon
These two programs have produced a detector with unparalleled capabilities
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The CollaborationThe CollaborationA strongly international venture:
11 nationsBrazil, China, France, Germany, India,
Israel, Japan, South Korea, Russia, Sweden, United States
51 institutions
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PHENIX at RHICPHENIX at RHIC
2 central spectrometers
2 forward spectrometers
3 global detectors
West
EastSouth
North
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ScheduleSchedule
2 central spectrometers
2 forward spectrometers
3 global detectors
1999
20002001
2002
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24-Jul-9724-Jul-97
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10-Jan-9810-Jan-98
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12-Jan-9912-Jan-99
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23-Dec-9923-Dec-99
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Run-1 Configuration
Run-1 Configuration
Two central arms Mechanically
~complete Roughly half of
aperture instrumented Global detectors
Zero-degree Calorimeters (ZDCs)
Beam-Beam Counters (BBCs)
Multiplicity and Vertex Detector (MVD, engineering run)
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TourTour
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Tour (Particle View)
Tour (Particle View)
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Run-1 Accomplishments
Run-1 Accomplishments
First collisions:15-Jun-00 Last collisions: 04-Sep-00 During this period:
Commissioned Zero-Degree Calorimeters Beam-Beam Counters Multiplicity and Vertex Counter Drift Chambers Pad Chambers Ring Imaging Cerenkov Counter Time Expansion Chamber Time-of-Flight Counters Electromagnetic Calorimeter Muon Identifier Minimum Bias Triggers Data Acquisition System
Recorded ~5M minimum bias events
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Run-1 ResultsRun-1 Results
This is a partial compilation
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Measuring InitialCollision GeometryMeasuring Initial
Collision Geometry
Zero Degree Calorimeters (ZDC) Sensitive to spectator
neutrons common to all four RHIC
experiments Using a combination of
the ZDC’s and BBC’s we can define Centrality Classes
Zero Degree Calorimeter
5-10%10-15%
15-20%
0-5 %
“Spectators”
“Spectators”
“Participants”. n
nnp
pp
Beam-Beam Counter (BBC)Impact Parameter
ZD
CBBC
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R2
Determining Energy DensityDetermining
Energy Density
Bjorken~ 5.0 GeV/fm3
Roughly 1.5 to 2 times higher than any previous experiments
Bjorken formula for thermalized energy density
time to thermalize the system (0 ~ 1 fm/c)~6.5 fm
For the most central events:
PHENIX preliminary
EMCAL
What is the energy density achieved? How does it compare to the expect
phase transition value ? Is this energy density thermalized?
dy
dE
RT
Bj0
2
11
dydz 0
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Have studied growth of Number of particles Energy
versus “centrality” Excellent consistency between two analyses First evidence for new term in growth ~ number
of collisions
PHENIX preliminaryPHENIX preliminary
collpart NBNAddX 0
28.088.0 A
12.034.0 B
First PublicationsFirst Publications
)(24.080.0 GeVA )(09.023.0 GeVB
19.038.0/ AB 18.029.0/ AB
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Fingerprinting Particles
Fingerprinting Particles
Combined Tracking Beam-Beam Counter Time-of-Flight array
provides excellent hadron identification over broad momentum band:
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Anti-proton/proton ratio
Anti-proton/proton ratio
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Approaching the Early Universe
Approaching the Early Universe
Early Universe: Anti-proton/proton = 0.999999999
√s [GeV]
PHENIX preliminary
E866Au+Au
NA44Pb+Pb
pba
r/p
We’ve created “pure” matterapproaching this value
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0 0 spectraspectra0 0 spectraspectra
0
pT >2 GeV,asym<0.8
Systematic errors includedMain sources:
peak extraction PID loss efficiency calculations non-vertex pions pT scale
Centrality ~Nbin ~Npart
10% 800 300 M.B. 125 75 75-92% 10 10 ~1M Min Bias AuAU events
s = 130 GeV
Peripheral
Min bias
Central
36
Charged pT SpectraCharged pT Spectra Systematic
trends in high momentum production also studied with charged particles Much greater
statistics Different
systematics
37
Comparison to charged spectraComparison to
charged spectra
0 spectra matches identified charged pion spectra –
A very good internal test of our results
(+ +-)/2
0
All charged
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Comparison to Theory
Comparison to Theory
Good agreement with “grazing” collisions
For head-on collisions, clear deficit with respect to “no new physics” calculations
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Central Events – What’s Going On?Central Events – What’s Going On?
“Standard” predictions overestimate the cross-sectionfor 0 by at least 5
dE/dx=0.25 GeV/fm
dE/dx = 0 (pQCD)
Predictions including (plasma-like!)energy loss consistent with 0
40
Physics Implications (??)
Physics Implications (??)
Slide fromseminar given lastmonth by M. Gyulassy
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Physics ImpactPhysics Impact
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Composition at high pT
Composition at high pT
Possible complication in comparisons of charged yields to theory:
Particle composition is observed to be a strong function of pT
43
Time to PhysicsTime to PhysicsAgain, learn from the past:
First CDF publication:Transverse-Momentum
Distributions of Charged Particles Produced in p-pbar Interactions at 630 and 1800 GeV, F. Abe et al., Phys. Rev. Lett. 61, 1819 (1988).
~One year from data-taking.
Much simpler final state!
We will be hard-pressed to reach this goal
And much harder-pressed to maintain “CDF-like” rate WRONG!(?)
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One Year AgoOne Year AgoFor years we’d been showing pictures of one “central” arm:
21-Jan-00: The real thing moves into place
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Shape of Things to Come
Shape of Things to Come
Completion of Central Arms Significantly
increased aperture Addition of new capabilities
South Muon Arm Di-muon physics
Upgraded Triggers Data Acquisition
The ~5M events recorded in Run-1 represent ~1 day of data-taking for RHIC+PHENIX in Run-2
Insert here
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Shape of Things NowShape of Things Now
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SummarySummary PHENIX detector has provided outstanding data in
first year of RHIC operations Measured
Charged multiplicity Transverse energy Elliptic flow Identified particle spectra HBT parameters High pT spectra Inclusive electron spectrum (much more)
Observed New trends in particle production New behavior in particle yields at high momentum
Ideally positioned to dramatically extend these results in second year of RHIC running