17-oct-03w.a. zajc 1 recent discoveries at rhic do they indicate a new state of matter? w.a. zajc...
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17-Oct-03 W.A. Zajc 1
Recent Recent Discoveries Discoveries
at RHIC at RHIC Do they indicate a Do they indicate a
new state of new state of matter?matter?
W.A. ZajcColumbia University
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2
From the National Research Council Committee on The Physics of the Universe:
Connecting Quarks with the Cosmos:
Eleven Science Questions for the New Century
It’s In The NewsIt’s In The News
No.
77Are there new
states of matter at ultrahigh
temperatures and densities?
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Fermi’s VisionFermi’s Vision
RHIC
From Fermi notes on Thermodynamics
(Almost) included RHIC physics See also remarks in his “statistical model” paper
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QCD is not QEDQCD is not QED QED (Abelian):
Photons have do not carry charge Flux is not confined 1/r potential 1/r2 force
QCD (Non-Abelian): Gluons carry charge (red, green, blue) (anti-red, anti-
green, anti-blue) Flux tubes form potential ~ r constant force
HOW TO LIBERATE ??
+ +…
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Relevant dimensionsRelevant dimensions Hadron masses ~ 1 GeV Hadron sizes ~ 10-15 meters
aka 1 femtometer
aka 1 fermi = 1 fm Characteristic velocity ~ c
Characteristic time ~ 1 fm/c
Planck’s constant = 0.2 GeV-fm 1 fm-1 200 MeV 200 MeV ~ characteristic scale associated
with confinement
c
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Relevant Nuclear PhysicsRelevant Nuclear Physics Nuclei are
(sort of) spherical contain A=N+Z protons and neutrons have ~ constant density 0 ~ 0.16 GeV /
fm3
MPROTON ~ MNEUTRON ~ 1 GeV R(A) = 0.92 A1/3 (rms) , where A = Atomic Number
<r2PROTON>1/2 ~ <r2
NEUTRON>1/2 ~ 0.86 fm Nuclei ~ close-packed “spheres” of protons and neutrons
Nuclear potential Short range ( ~ 1 fm) Modest strength ( ~ 50 MeV depth) Nuclei are loosely bound Treat as ~free Fermi gas of protons and neutrons
Nuclear physics is the “Large A, small Q2” limit of QCD
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Need better control of dimensional analysis:
Relevant Thermal PhysicsRelevant Thermal PhysicsQ. How to liberate quarks and gluons from
~1 fm confinement scale?A. Create an energy density
??densitynuclear Normal ~fm GeV /2.0~)fm1/(~ 34
42
30Tg
Energy density for “g” massless d.o.f
42
303222
8
782 Tcfasg
8 gluons, 2 spins;
2 quark flavors, anti-quarks, 2 spins, 3 colors
3
4
4 fm GeV /4.21
1212
fmT
“Reasonable” estimate
42
3037 T 37 (!)
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37 B,- 90
42
gTgPQGP
Pressure in plasma phase with “Bag constant” B ~ 0.2 GeV / fm3
42
903 TP
Pressure of “pure” pion gas at temperature T
Slightly More Refined Slightly More Refined EstimateEstimate
Phase transition at T ~ 140 MeV with latent heat ~0.8 GeV / fm3
-0.25
0
0.25
0.5
0 100 200
Temperature (MeV)
Pressure
(GeV / fm3)
Pion Phase
QGP Phase PQGP
P
Select system with higher pressure:
Compare to best estimates (Karsch, QM01) from lattice calculations:
T ~ 150-170 MeV latent heat ~ 0.70.3 GeV / fm3
Compare
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~1970: An Ultimate ~1970: An Ultimate Temperature?Temperature?
The very rapid increase of hadron levels with mass
Hadron 'level' diagram
0
500
1000
1500
0 10 20 30 40
Degeneracy
Mass (MeV)
Kfo
Density of States vs Energy
0
50
100
150
200
250
0 500 1000 1500 2000
Mass (MeV)
Number of available
states
~ equivalent to an exponential level density
HT /maem~dmdn
(m)ρ
dmem~
dm(m)eρ
)T1
T1
m(a
T /m
H
and would thus imply a “limiting temperature”TH ~ 170 MeV Hagedorn,
S. Fraustchi, Phys.Rev.D3:2821-
2834,1971
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(1970) T(1970) TH H (2000) (2000) TTCC
That is: The ‘Hagedorn temperature’ TH is now understood as a precursor of TC
TC = Phase transition temperature of QCD
0.66 TCT =0
0.90 TC
1.06 TC
F. Karsch, hep-ph/0103314
Current estimates from lattice calculations:
TC ~ 150-170 MeV
L ~ 0.70.3 GeV / fm3
(latent heat)
Study confining potentialin Lattice QCD at various temperatures
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Making Something from NothingMaking Something from Nothing
Experimental method:Energetic collisions of heavy nuclei
Experimental measurements:Use probes that are Auto-generated Sensitive to all time/length scales
Perturbative Vacuum
cc
MeV 200 ~)f 1(/~ etemperatur requires mT
Color Screening
cc
Explore non-perturbative “vacuum” that confines color flux by melting it
Particle production Our ‘perturbative’ region
is filled with gluons quark-antiquark pairs
which screen the “bare” interaction
A Quark-Gluon Plasma (QGP)
Non-perturbative Vacuum
Perturbative Vacuum
cc
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The Early Universe, Kolb and Turner
Previous AttemptsPrevious Attempts First attempt at QGP formation was successful
(~1010 years ago)
03
3
/)(42* )2(1
)(
30/
1)(
pd
e
pE
TTg
iii TEi
species
( Effective number of degrees-of-freedom per relativistic particle )
g
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RHIC SpecificationsRHIC Specifications 3.83 km
circumference Two independent
rings 120 bunches/ring 106 ns crossing time
Capable of colliding ~any nuclear species on ~any other species
Energy:
500 GeV for p-p 200 GeV for Au-Au
(per N-N collision) Luminosity
Au-Au: 2 x 1026 cm-2 s-1
p-p : 2 x 1032 cm-2 s-1 (polarized)
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RHIC Runs To DateRHIC Runs To Date Run-1 (2000):
Au-Au at 130 GeV ~ 1 b-1 (p-p equivalent: ~ 0.04 pb-1)
Run-2 (2001-2): Au-Au at 200 GeV ~ 24 b-1
(p-p equivalent: ~ 1 pb-1)
p-p at 200 GeV 0.15 pb-1
Run-3 (2002-3): d-Au at 200 GeV 2.7 nb-1
(p-p equivalent: ~ 1 pb-1)
p-p at 200 GeV 0.35 pb-1
RHIC Successes (to date) based on ability to deliver
physics at ~all scales:
barn : Multiplicity (Entropy)
millibarn: Flavor yields (temperature)
microbarn: Charm (transport)
nanobarn: Jets (density)
picobarn: J/Psi (deconfinement)
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How is RHIC Different?How is RHIC Different? Different from p-p, e-p colliders
Atomic weight A introduces new scale Q2 ~ A1/3 Q02
Different from previous (fixed target) heavy ion facilities ECM increased by order-of-magnitude
Accessible x (parton momentum fraction)decreases by ~ same factor
Access to 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
s
p 2~x T
Jargon Alert:
s = Center-of-mass energy (per nucleon collision)
pT = transverse momentum = |p| sin
Q2 = (momentum transfer)2
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1 RHIC Event1 RHIC EventData Taken June 25, 2000.
Pictures from STAR Level 3 online display.
Q. How to take the measure of such complexity??
(Is it possible?)
A. (Yes.) Begin with single-particle momentum spectra
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Kinematics 101Kinematics 101Fundamental single-particle observable:
Momentum Spectrum
3
3
dp
dE
dypd
d
pE
pEy
Tz
z
2
3
ln2
1
dy
dn
pd
d
T
2
2
0
5
1 0
1 5
2 0
2 5
3 0
-1 -0.5 0 0.5
cos
)(cosd
dn
0
0 .2
0 .4
0 .6
0 .8
1
1 .2
1 .4
1 .6
-6 -4 -2 0 2 4 6
y
dy
dn
0
0 .2
0 .4
0 .6
0 .8
1
1 .2
1 .4
1 .6
-6 -4 -2 0 2 4 6
y
dy
dn
Kinematics
Dynamics
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(PID) Acceptances(PID) Acceptances
STAR AcceptanceSTAR Acceptance
PHOBOS AcceptancePHOBOS AcceptanceBRAHMS AcceptanceBRAHMS Acceptance
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Transverse Transverse DynamicsDynamics
The ability to access “jet” physics also clearly anticipated in RHIC design manual (vintage: ISAJET) a new perturbative
probe of the colliding matter
Most studies to date have focused on single-particle“high pT” spectra Please keep in
mind:“High pT” is lower
than you think
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Focus on some slice of the collision: Assume 3 nucleons struck
in A, and 5 in B Do we weight this
contribution as Npart ( = 3 + 5) ? Ncoll ( = 3 x 5 ) ?
Answer is a function of pT
: Low pT large cross
sections yield ~Npart Soft, non-perturbative,
“wounded nucleons”, ... High pT small cross
sections yield ~Ncoll Hard, perturbative,
“binary scaling”, point-like, A*B, ...
Predicting pPredicting pTT Distributions at Distributions at RHICRHIC
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LuminosityLuminosity Consider collision of ‘A’ ions per bunch
with ‘B’ ions per bunch:
Luminosity
A
A
B
B
Cross-sectional area ‘S’
S
BAL
~
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Change scale by ~ 10Change scale by ~ 1099
Consider collision of ‘A’ nucleons per nucleuswith ‘B’ nucleons per nucleus:
‘Luminosity’
A
A
B
B
Cross-sectional area ‘S’
BANS
BAL Coll
~~
Provided:
No shadowing
Small cross-sections
BANnot Part
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Q. Why did we build Q. Why did we build RHIC?RHIC?
A: To gain access to ‘small’ cross-sections* that areA) FundamentalB) CalculableC) Interesting
which then allow us to useNcoll ( aka A*B or “binary” or “point-like”)
scaling of yields as our
baseline hypothesis
for probing a new state of matter
(This of course one of many possible answers…)
}p+p → 0+X (200 GeV)
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Binary Collisions
Participants
b (fm)
Systematizing our Systematizing our KnowledgeKnowledge
All four RHIC experiments have carefully developed techniques for determining the number of participating
nucleons NPART in each collision(and thus the impact parameter)
The number of binary nucleon-nucleon collisions NCOLL as a function of impact parameter
This effort has been essential in making the QCD connection Soft physics ~ NPART
Hard physics ~ NCOLL
Often express impact parameter b in terms of “centrality”, e.g., 10-20% most central collisions
Participants
Spectators
Spectators
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Example of NExample of Ncollcoll Scaling Scaling
Q: Are there rare probes at RHIC that scale as the number of binary collisions?
A: Yes, charm production (for Ncoll from 71 to 975)
PHENIX Run-2 Preliminary Data presented at Quark Matter 2002
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Tremendous interest in hard scattering (and subsequent energy loss in QGP) at RHIC Production rate calculable
in pQCD But strong reduction
predicted due to dE/dx ~ path-length (due to non-Abelian nature of medium)
However: “Traditional” jet
methodology very difficult at RHIC
Dominated by the soft background
Investigate by (systematics of) high-pT single particles
‘‘Jets’ at RHICJets’ at RHIC
RJet
Axis
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Another Example of NAnother Example of Ncollcoll
ScalingScaling
PHENIX (Run-2) data on 0 production in peripheral collisions:
Excellent agreement between PHENIX measured 0’s in p-p
and
PHENIX measured 0’s in Au-Au peripheralcollisions scaled by the number of collisions
over ~ 5 decades PHENIX Preliminary
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Central Collisions Are Central Collisions Are Profoundly Profoundly DifferentDifferent
Q: Do all processes that should scale with Ncoll do just that?
A: No! Central collisions
are different .(Huge deficit at high pT)
This is a clear discoveryof new behavior at RHIC
Suppression of low-x gluons in the initial state?
Energy loss in a new state of matter?
PHENIX Preliminary
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Energy Loss of Fast Energy Loss of Fast PartonsPartons
Many approaches 1983: Bjorken
1991: Thoma and Gyulassy (1991)
1993: Brodsky and Hoyer (1993)
1997: BDMPS- depends on path length(!)
1998: BDMS
Numerical values range from ~ 0.1 GeV / fm (Bj, elastic scattering of partons) ~several GeV / fm (BDMPS, non-linear interactions of
gluons)
222
2
2 4ln~
4ln
4
303
M
ETT
M
ET
dx
dESS
D
SF
ETC
dx
dE
ln3
4 22
2
2Tk
dx
dE
gg
DRS
LL
C
dx
dE
ln
8
2
24
2TC
s
kN
dx
dE
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Systematizing Our Systematizing Our ExpectationsExpectations
Describe in terms of scaled ratio RAA
= 1 for “baseline expectations”
Will present most of suppression data in terms of this ratio
“no effect”
Events pp in YieldBAEvents Au Auin Yield
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Is The Suppression Unique to Is The Suppression Unique to RHIC?RHIC?
Yes- all previous nucleus-nucleus measurements see enhancement, not suppression.
Effect at RHIC is
qualitatively new physics made accessible by RHIC’s ability to produce (copious) perturbative
probes (New states of matter?)
Run-2 results show that this effect persists (increases) to
the highest available transverse momenta
Describe in terms of scaled ratio RAA
= 1 for “baseline expectations”
Events pp in YieldBAEvents Au Auin Yield
ISR 31 GeV
RHIC 200 GeV
SPS 17 GeV
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Is The Suppression Always Seen at Is The Suppression Always Seen at RHIC?RHIC?
NO! Run-3: a crucial control measurement via d-Au
collisions
d+Au results from
presented at a press conference at BNL on June, 18th, 2003
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First ConclusionFirst Conclusion The combined data from Runs 1-3 at
RHIC on p-p, Au-Au and d-Au collisions establish that a new effect (a new state of matter?) is produced in central Au-Au collisions
Au + Au Experiment d + Au Control Experiment
Preliminary DataFinal Data
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Theoretical Understanding?Theoretical Understanding?
Both Au-Au suppression (I. Vitev and M. Gyulassy,
hep-ph/0208108) d-Au enhancement (I. Vitev, nucl-th/0302002 )
understood in an approach that combines multiple scattering with absorption in a dense partonic medium
Our high pT probeshave been calibratedand are nowbeing used toexplore the precise propertiesof the medium
Au-Au
d-Au
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Further EvidenceFurther Evidence
C2(Au Au)C2(p p) A* (1 2v22 cos(2))
STAR azimuthal correlation function shows ~ complete absence of “away-side” jet
Surface emission only (?) That is, “partner” in hard
scatter is absorbed in the dense medium
GONE
GONE
Pedestal&flow subtracted
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RecombinationRecombination The in vacuo fragmentation
of a high momentum quark to produce hadrons competes with the in medium recombination of lower momentum quarks to produce hadrons
Example: Fragmentation: Dq→h(z)
produces a 6 GeV/c from a 10 GeV/c quark
Recombination: produces a 6 GeV/c
from two 3 GeV/c quarks produces a 6 GeV/c proton
from three 2 GeV/c quarks
Fries, et al, nucl-th/0301087
Greco, Ko, Levai, nucl-th/0301093
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Recombination Meets Recombination Meets DataData
Provides a “natural” explanation of Spectrum of charged hadrons Enhancements seen in p/ Momentum scale for same
Fries, et al, nucl-th/0301087
...requires the assumption of a thermalized parton phase... (which) may be appropriately called a quark-gluon plasma
Fries et al., nucl-th/0301087
“Extra” protons sampled from ~pT/3
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Evidence that
initial spatial asymmetry is translated quickly to momentum space ( as per a
hydrodynamic description)
Hydrodynamics of Elliptic Hydrodynamics of Elliptic FlowFlow
Parameterize azimuthal asymmetry of charged
particles as
dn/d ~ 1 + 2 v2 cos (2 )
x
z
y
(scaled) spatial asymmetry
(PHOBOS : Normalized Paddle Signal)
Hydrodynamic limit
STAR: PRL86 (2001) 402
PHOBOS preliminary
Hydrodynamic limit
STAR: PRL86 (2001) 402
PHOBOS preliminary
Compilation and Figure from M. Kaneta
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Recombination Recombination TestedTested
The complicated observed flow pattern in v2(pT) d2n/dpTd ~ 1 + 2 v2(pT) cos (2 )
is predicted to be simple at the quark level under pT → pT / n , v2 → v2 / n , n = 2,3 for meson,baryon
if the flow pattern is established at the quark level Compilation
courtesy of H. Huang
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Second ConclusionsSecond Conclusions Suppression at high pT is characteristic of
dense matter formation in Au-Au collisions(lack of suppression for heavy quarks, as observed in
Ncoll scaling of charm yields, also predicted)
Recombination models operating at the parton level describe “Anomalous” baryon/meson yields
(i.e., jet fragmentation is augmented by “other” partons)
Elliptic flow patterns for different mesons and baryons(results from one primordial flow pattern established at the parton level)
Is there evidence that these (deconfined?) partons are also thermalized?
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Just a sample!There are also results on spectra of 0‘s, K* , , , , …
Results on Particle CompositionResults on Particle Composition
BRAHMS: 10% centralPHOBOS: 10%PHENIX: 5%STAR: 5%
200 GeV/A Au+Au
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Longitudinal Longitudinal DynamicsDynamics
From the RHIC design manual: Emphasis on higher beam
energy needed to develop “baryon-free” central region
This theoretical argument is nicely confirmed by measurements from BRAHMS
Aids in (future) comparisons to lattice gauge theory conditions in the early
universe
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Central
Ratio (data)
Rat
io (
chem
ical
fit
)
BRAHMSPHENIXPHOBOSSTAR
K /K
/ / /
p/p
K/hK /h K
s/h
K / K / p/p/
K/h /h /h
/h
/h/h
Model:N.Xu and M.Kaneta,
nucl-ex/0104021
Is there a ‘Temperature’?Is there a ‘Temperature’? Apparently:
Assume distributions described by one temperature T and
one ( baryon) chemical potential :
One ratio (e.g., p / p ) determines / T :
A second ratio (e.g., K / ) provides T Then predict all other hadronic yields and ratios:
pdedn E 3/)(~ Tμ
TμTμ
Tμ/2
/)(
/)(
ee
e
p
pE
E
130 GeV RHIC : STAR / PHENIX / PHOBOS / BRAHMS
17.4 GeV SPS : NA44, WA97
STAR preliminary Systematic errors ~10-20%
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Previous figure RHIC has net baryon density ~ 0: TCH = 179 ± 4 MeV, B = 51 ± 4 MeV (M. Kaneta and N. Xu, nucl-ex/0104021)
130 GeV RHIC : STAR / PHENIX / PHOBOS / BRAHMS
17.4 GeV SPS : NA44, WA97
STAR preliminary Systematic errors ~10-20%
Locating RHIC on Phase Locating RHIC on Phase DiagramDiagram
RHIC is as close as we’ll get to the early universe for some time
Previous Heavy Ion Experiments (CERN SPS)
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QuestionsQuestions Do those many particles in the final
state have anything to do with a state of matter?
For example: Is there a well-defined Energy density Temperature T Chemical potential Size R Transport coefficient
Answer: Yes (apparently) The first round of RHIC experiments have
determined ~all of these parameters (and more)
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Open QuestionsOpen Questions Is the quark-gluon plasma being formed in
RHIC collisions? To be determined: Does charmonium show the expected suppression
from (color) Debye screening?
Is there direct (photon) radiation from the plasma? Do the suppression effects extend to the highest pT’s?
What is the suppression pattern in cold nuclear matter? (proton-nucleus collisions)
What are the gluon and sea-quark contributions to the proton spin? (polarized proton running)
RHIC
First results now available!
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Screening by the QGPScreening by the QGP (An explicit test of deconfinement) In
pictures:
QCD potential at T=0
r -->
V(r
)
QCD potential at high T
r -->
V(r
)
QCD potential at high T and
high density
r -->
V(r
)
Non-perturbative Vacuum
Perturbative Vacuum
cc
Perturbative Vacuum
cc
Color Screening
cc
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Screening by the QGPScreening by the QGPIn first-order finger physics:
Follow usual derivation of Debye screening
Now put in QGP scales and assumptions:
Hadrons with radii greater than ~ D will be dissolved
Study “onium” bound states
oD
Do
kTekTeo
ne
kTkTne
een
2
2
22
//2
42 with
1/2 4
44
fm 0.41
2
1
MeV 200
QGP)for Boltzman -(Stefan 6.3
1~433
22
gT
T
TTn
ge
D
o
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J/J/ Measurements To Measurements To DateDate
p-p results: ~comparable
to other hadron facilities (especially at low pT)
Au-Au results: A limit only To be addressed
in Run-4
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Looking AheadLooking Ahead Runs 1-5: EXPLORATION
Well underway! “Complete” data sets for full energy
Au-Au d-Au
200 GeV p-p “Complete” data set for A-A comparison Strong start on G physics
Runs 5-10: CHARACTERIZATION Ion program
Species scans Energy “scans” d-A, p-A
Spin program “Complete” program of G(x) at 200 GeV 500 GeV running, sea quark contributions Study of G(x) via direct photons, heavy flavor (energy
scan?) Upgrades (as available) to extend reach of both
programs Runs 11-15: EXPLOITATION
Full upgrades available Repeat “complete” measurements with x10-100
sensitivity
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On The Nature of On The Nature of DiscoveryDiscovery
Discovery of Top
“Discovery” of QCD
“Discovery(?)” that gluon Is massless
It is clear that RHIC physics is on the cusp “Evidence for” QGP is abundant “Discovery of” same is imminent
QCD Publications Versus Time
0
100
200
300
400
500
600
1970 1975 1980 1985 1990 1995 2000
Year
SP
IRE
S E
ntr
ies
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“It’s a Quark-Gluon-Plasma, Period.”
Miklos GyulassyColumbia University
Three major discoveries at RHIC1) Conclusive evidence for PQCD via v2 collective flow of 104 , K, p2) Conclusive evidence for pQCD jet quenching in Au+Au at RHIC3) Conclusive evidence for dA via jet unquenching in dAu: Null Control
All 3 are explained by QCD dynamics
Conclusion: AuAu at 200 AGeV made Bulk QGP Matter
00.2 fm/c( ~ ) 100et e:
QGP =PQCD + pQCD + dA
Provocative (non)-Provocative (non)-QuestionsQuestions
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“If we were sure it was the quark-gluon plasma, we would have said it was.“, W.A.Zajc.
"It is without a doubt the densest matter ever created in the laboratory," said W. A. Zajc
"We're creating matter that is tremendously denser," said Peter Jacobs, "It makes no sense to talk about individual protons and
neutrons."
"Most of us aren't quite ready to make that leap," T. Hemmick said.
Open(?) Questions
“The experimentalists' caution may be due, in part, to fallout from a previous claim regarding quark soup at CERN [(6/20/00)] . Many physicists called the CERN data unconvincing.” (Newsday 6/17/03)
New York Times 6/19/03
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Closed QuestionsClosed Questions Has the accelerator worked?
Have the experiments worked?
Are the data analyzable?
Are they being analyzed?
Do the data validate the premise of RHIC? Collective, ~thermal behavior Contact with basic QCD phenomenology
Are there new phenomena?
Are there prospects for a long and fruitful experimental program?
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Is the Suppression New?Is the Suppression New? Yes- in the sense that an enhancement
is observed in proton-nucleus collisions: Known since 1975 that
yields increase as A, > 1
J.W. Cronin et al.,Phys. Rev. D11, 3105 (1975)
D. Antreasyan et al.,Phys. Rev. D19, 764 (1979)
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Other New EffectsOther New Effects Comparison of Au-Au, d-Au and p-p data indicate
Dense matter uniquely formed in Au-Au collisions How dense? Sufficient to “extinguish” jets
Q. Are there other anomalies observed in these collisions?A. Yes- the fragmentation function is drastically modified:
Q. How to understand this?
A. CompetitionbetweenFragmentation
andRecombination
at the quark level
(next slide)
Peripheral
Central
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Experimental Gauge Experimental Gauge TheoryTheory
QCD is the only fundamental gauge theory amenable to experimental study in both Weak and strong coupling limits Particle and bulk limits
RHIC (Strong, bulk ) limit : heavy ion collisions (Strong, particle) limit : spin physics (Weak , particle) limit : W’s as helicity probes (Weak , bulk ) limit : high pT probes of
plasma state
Coupling Constant Number Limit
Weak Strong Particle Bulk
Gravity X X
Weak X X
QED X
QCD
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My 3 Part Definition of a QGP
1. A form of matter (many body dynamical system) with a unique set of Bulk (collective)
phenomena and partonic diagnostics
2. which are calculable in the deconfined (Colored) quark-gluon basis of QCD
3. And which can be turned on or off via Control experiments
Examples of NON-QGP systems in QCD1. e+e- -> q q g 2 ok but not 12. p+p -> pi, K, p 2 ok but not 13. e+A -> jets 2 ok but not 14. Nucleus A 1 ok but not 25. SIS,AGS res. gas 1 ok but not 2 6. SPS A+A 1 ok but 2~OK but not 3!
QGP =PQCD + pQCD + dA
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CERES/SPS
Below RHIC energies, QCD hydro over-predicts elliptic flow!
2 2chdN /dyd x (fm )-
^
v2(Ecm) QGP hydro for the FIRST time at RHIC!
17 AGeV
CERES 17 AGeV
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Yet Another Luminosity Limited Yet Another Luminosity Limited ObservableObservable
New PHENIX Run-2 result on v2 of 0’s:
Clearly wouldbenefit from Run-4 statistics PHENIX Preliminary