# Wisconsin by qingyunliuliu

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```									              Recent
Discoveries
at RHIC
Do they indicate a new
state of matter?
W.A. Zajc
17-Oct-03          W.A. University
ColumbiaZajc           1
It‟s In The News
2

No.

7
Are there new
states of matter
From the National Research Council Committee on
at ultrahigh
The Physics of the Universe:              temperatures
Connecting Quarks with the Cosmos:        and densities?
Eleven Science Questions for the New Century

17-Oct-03                                                               W.A. Zajc
Fermi‟s Vision
3

   (Almost) included RHIC physics

RHIC

From Fermi notes on
Thermodynamics

17-Oct-03                                                              W.A. Zajc
QCD is not QED
4

     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 ??

+               +…

17-Oct-03                                                                            W.A. Zajc
The Landscape of QCD
5

17-Oct-03                          W.A. Zajc
Relevant dimensions
6

   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       c = 0.2 GeV-fm
 1 fm-1  200 MeV
 200 MeV ~ characteristic scale associated
with confinement

17-Oct-03                                                     W.A. Zajc
7

Relevant Nuclear Physics
   Nuclei are
   (sort of) spherical
   contain A=N+Z protons and neutrons
    have ~ constant density r0 ~ 0.16 GeV / fm3

 MPROTON ~ MNEUTRON ~ 1 GeV
 R(A) = 0.92 A1/3 (rms) , where A = Atomic Number

 <r2PROTON>1/2 ~ <r2NEUTRON>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 Q 2” limit of QCD

17-Oct-03                                                                    W.A. Zajc
8

Relevant Thermal Physics
Q. How to liberate quarks and gluons from
~1 fm confinement scale?
A. Create an energy density
  ~ ( / 1 fm )4 ~ 0.2 GeV / fm 3 ~ Normal nuclear density ??
 Need better control of dimensional analysis:
2
g            T4                    Energy density for “g” massless d.o.f
30
8 gluons, 2 spins;
                                  
2
7                                 2 quark flavors, anti-quarks,
 2  8 g   2 s  2 a  2 f  3 c  T 4
         8                         30          2 spins, 3 colors

2                                            37 (!)
 37         T4
30                4
                                 “Reasonable”
 12  T  12  
4
  2.4 GeV / fm 3
 1 fm 
                                       estimate
17-Oct-03                                                                                  W.A. Zajc
9

Slightly More Refined Estimate
     Compare
2
P  3           T4       Pressure of “pure” pion gas at temperature T
90
2                              Pressure in plasma phase with
PQGP  g               T 4 - B, g  37
90                               “Bag constant” B ~ 0.2 GeV / fm3
       Select system with higher pressure:
0.5
Pion Phase
QGP Phase
PQGP         Phase transition at T ~ 140 MeV
with latent heat ~0.8 GeV / fm3
0.25

Pressure                                            P         Compare to best estimates (Karsch, QM01)
(GeV / fm 3)
from lattice calculations:
0
0            100              200
T ~ 150-170 MeV
latent heat ~ 0.70.3 GeV / fm3
Temperature (MeV)

-0.25
17-Oct-03                                                                                            W.A. Zajc
10

~1970: An Ultimate Temperature?
    The very rapid increase of                                  1500

~ equivalent to an exponential
1000

Mass                              rw
level density                                     (MeV)                   fo
h
500            K

dn
ρ
(m)
    ~ ma e m / TH                                                   
dm                                                    0
0             10            20        30          40
Degeneracy
 ρ
Density of States vs Energy
m / T
(m)e                    dm                              250

1 1                                   200
m(  )
~  ma e     TH T
dm                 Number of 150
available
states 100
   and would thus imply a
“limiting temperature”                                         50

TH ~ 170 MeV                        Hagedorn,                  0
0        500           1000      1500      2000
S. Fraustchi,
Phys.Rev.D3:2821-2834,1971                                  Mass (MeV)
17-Oct-03                                                                                                                        W.A. Zajc
(1970) TH  (2000) TC
11

That is: The „Hagedorn temperature‟ TH is now understood
as a precursor of TC
TC = Phase transition temperature of QCD
0.66 TC     Study
T =0
confining
potential
in Lattice QCD
at various
0.90 TC
temperatures
Current estimates from
lattice calculations:

1.06 TC     TC ~ 150-170 MeV

F. Karsch, hep-              L ~ 0.70.3 GeV / fm3
ph/0103314
(latent heat)

17-Oct-03                                                            W.A. Zajc
12

Making Something from Nothing
    Explore non-perturbative “vacuum”                 Non-perturbative Vacuum
that confines color flux by melting it
requires temperatur e T ~  / (1 fm ) ~ 200 MeV      c                c
 Particle production
 Our „perturbative‟ region
Perturbative Vacuum

is filled with
 gluons
 quark-antiquark pairs
which screen the “bare” interaction           c                c
 A Quark-Gluon Plasma (QGP)
     Experimental method:                                 Perturbative Vacuum
Energetic collisions of heavy nuclei
     Experimental measurements:
Use probes that are
c                c
   Auto-generated
   Sensitive to all time/length scales
Color Screening
17-Oct-03                                                                    W.A. Zajc
Previous Attempts
13

First attempt at QGP formation was successful

(~1010 years ago)

1                       E i ( p)              d3 p
g* (T )  2 4
 T / 30
 e
species 0
( E i   i ) / Ti
 1 ( 2 )3
g
( Effective
number of
degrees-
The Early Universe,                                        of-
Kolb and Turner
freedom
per
relativistic
particle )

17-Oct-03                                                                                        W.A. Zajc
RHIC Specifications
14

    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)

17-Oct-03                                            W.A. Zajc
RHIC Runs To Date
15

    Run-1 (2000):                               RHIC Successes (to date)
   Au-Au at 130 GeV ~ 1 b-1             based on ability to deliver
(p-p equivalent: ~ 0.04 pb-1)          physics at ~all scales:
barn    : Multiplicity (Entropy)
    Run-2 (2001-2):
    Au-Au at 200 GeV ~ 24 b-1        millibarn: Flavor yields
(p-p equivalent:  ~ 1 pb-1)        (temperature)
microbarn: Charm (transport)
 p-p      at 200 GeV 0.15 pb-1
nanobarn: Jets (density)
    Run-3 (2002-3):                          picobarn: J/Psi (deconfinement)
   d-Au at 200 GeV        2.7 nb-1
(p-p equivalent:       ~ 1 pb-1)

   p-p    at 200 GeV     0.35 pb-1

17-Oct-03                                                                         W.A. Zajc
How is RHIC Different?
16

   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
2 pT
Accessible x (parton momentum fraction) x ~
decreases by ~ same factor                    s

 Non-linear dE/dx           s = Center-of-mass energy (per nucleon collision)
pT = transverse momentum = |p| sin q
Q2 = (momentum transfer)2

   Its detectors are comprehensive
~All final state species measured with a suite of detectors that
nonetheless have significant overlap for comparisons

17-Oct-03                                                                                      W.A. Zajc
RHIC‟s Experiments
17

STAR

17-Oct-03                        W.A. Zajc
1 RHIC Event
18

Data 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

17-Oct-03                                                                  W.A. Zajc
Kinematics 101
19

Fundamental single-particle observable:
Momentum Spectrum

dn
d 3s
E 3                               d (cos q )
dp
Kinematics

-1        -0.5          0        0.5
cosq
1  E  pz       d s
3
y    ln       
E p  
dn
2       z    d 2 pT dy          dy

Dynamics            -6   -4          -2     0    2         4   6
y

d 2s dn           dn

2
d pT dy            dy
-6   -4          -2     0    2         4   6
y

17-Oct-03                                                                                              W.A. Zajc
(PID) Acceptances
20

PHOBOS Acceptance
BRAHMS Acceptance

STAR Acceptance

17-Oct-03                                             W.A. Zajc
Transverse Dynamics
21

     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
“High pT” is lower than
you think
17-Oct-03                                      W.A. Zajc
22

Predicting pT Distributions at RHIC
    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, ...

17-Oct-03                                                       W.A. Zajc
Luminosity
23

     Consider collision of „A‟ ions per bunch
with                  „B‟ ions per bunch:

Cross-sectional
area ‘S’


A
Luminosity
B
A B
L~
S
17-Oct-03                                                          W.A. Zajc
Change scale by ~ 109
24

     Consider collision of „A‟ nucleons per nucleus
with                  „B‟ nucleons per nucleus:

Cross-sectional
area ‘S’

A
     „Luminosity‟
B
A B                               Provided:
L~      ~ N Coll  A  B                    No shadowing
S
Small
not    N Part  A  B            cross-sections
17-Oct-03                                                                    W.A. Zajc
Q. Why did we build RHIC?
25

p+p → 0+X (200 GeV)
that are
A) Fundamental
B) Calculable
C) Interesting
which then allow us to use
}
Ncoll ( 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…)

17-Oct-03                                                                     W.A. Zajc
26

Systematizing our Knowledge
     All four RHIC experiments have
carefully developed techniques                     Spectators

for determining
Participants
    the number of participating
nucleons NPART in each collision             Spectators
(and thus the impact parameter)
    The number of binary nucleon-
nucleon collisions NCOLL as a         Binary Collisions
function of impact parameter
     This effort has been essential in
making the QCD connection
    Soft physics ~ NPART
    Hard physics ~ NCOLL
     Often express impact
Participants
parameter b in terms of
“centrality”, e.g., 10-20% most
17-Oct-03
b (fm) Zajc
W.A.
Example of Ncoll Scaling
27

   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

17-Oct-03                                                                       W.A. Zajc
„Jets‟ at RHIC
28

     Tremendous interest in hard
scattering (and subsequent                    Jet
R   Axis
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:
very difficult at RHIC
   Dominated by the soft
background
 Investigate by (systematics of)
high-pT single particles

17-Oct-03                                                   W.A. Zajc
29

Another Example of Ncoll Scaling

   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 peripheral
collisions scaled by
the number of collisions

PHENIX Preliminary

17-Oct-03                                                             W.A. Zajc
30

Central Collisions Are Profoundly Different

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 discovery
of new behavior at RHIC

 Suppression    of
low-x gluons in
the initial state?
 Energy loss in
a new state of matter?    PHENIX Preliminary

17-Oct-03                                                      W.A. Zajc
31

Energy Loss of Fast Partons
    Many approaches
dE 3 30 2       4 ET            4 ET 
          S  ln 2  ~  S T 2 ln 2 
2
   1983: Bjorken                        dx   4          M               M 
dE 4                 E          
1991: Thoma and Gyulassy (1991)                       C F S T 2 ln             
2
                                                                                    
dx   3                D          
kT
2
   1993: Brodsky and Hoyer (1993)                        
dE

dx      2
dE      CR D
2
 L
   1997: BDMPS- depends on path length(!)             S         L ln  
 
dx       8 g         g
kT
2
   1998: BDMS                                       
dE     N
 s C
dx      4             2

    Numerical values range from
       ~ 0.1 GeV / fm (Bj, elastic scattering of partons)
   ~several GeV / fm (BDMPS, non-linear interactions of gluons)

17-Oct-03                                                                                          W.A. Zajc
32

Systematizing Our Expectations
       Describe in terms of
scaled ratio RAA                “no effect”

Yield in Au  Au Events

A  B Yield in p  p Events

= 1 for “baseline
expectations”

       Will present most of
suppression data in
terms of this ratio

17-Oct-03                                                   W.A. Zajc
33

Is The Suppression Unique to RHIC?
   Yes- all previous
nucleus-nucleus
measurements see
enhancement,
not suppression.
SPS 17 GeV
   Effect at RHIC is
ISR 31 GeV         qualitatively new physics
ability to produce
   (copious) perturbative
probes
   (New states of matter?)
RHIC 200 GeV      Run-2 results show that this
effect persists (increases) to
the highest available
transverse momenta

   Describe in terms of
scaled ratio RAA
Yield in Au  Au Events

A  B Yield in p  p Events
= 1 for “baseline expectations”
17-Oct-03                                                                     W.A. Zajc
34

Is The Suppression Always Seen at 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

17-Oct-03                                                        W.A. Zajc
First Conclusion
35

   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

Final Data               Preliminary Data

17-Oct-03                                                              W.A. Zajc
36

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                                          d-Au
high pT probes
have been
calibrated
and are now                              Au-Au
being used to
explore the
precise properties
17-Oct-03                                                                  W.A. Zajc
37

Further Evidence
    STAR azimuthal
correlation
function shows
~ complete            G                                             G
absence of            O
N
O
N
“away-side” jet       E                                             E

Pedestal&flow subtracted

C2 (Au  Au)  C2 (p  p)  A *(1 2v 2 cos(2 ))
2

 Surface emission only (?)
 That is, “partner” in hard scatter
      is absorbed in the dense medium
17-Oct-03                                                               W.A. Zajc
Recombination
38

   The in vacuo fragmentation of a
high momentum quark to
competes with the in medium
recombination of lower
momentum quarks to produce
   Example:
   Fragmentation: Dq→h(z)
   produces a 6 GeV/c 
from a 10 GeV/c quark
Fries, et al, nucl-th/0301087
   Recombination:                 Greco, Ko, Levai, nucl-th/0301093
 produces a 6 GeV/c 
from two 3 GeV/c quarks
 produces a 6 GeV/c proton
from three 2 GeV/c quarks

17-Oct-03                                                                      W.A. Zajc
Data
39

     Provides a “natural” explanation of
   Spectrum of charged hadrons       ...requires the assumption of a thermalized
parton phase... (which) may be appropriately
   Enhancements seen in p/          called a quark-gluon plasma
   Momentum scale for same           Fries et al., nucl-th/0301087

“Extra” protons sampled
from ~pT/3

Fries, et al, nucl-th/0301087

17-Oct-03                                                                                   W.A. Zajc
Hydrodynamics of Elliptic Flow
40

Parameterize azimuthal asymmetry of charged particles as
dn/d ~ 1 + 2 v2 cos (2 )                                 z

asymmetry
(scaled) spatial Hydrodynamic limit
STAR: PRL86 (2001) 402
y
PHOBOS preliminary
x
Evidence that initial
spatial asymmetry is
translated quickly to
momentum space
( as per a hydrodynamic
description)

Compilation and Figure from M. Kaneta
17-Oct-03                                                                                          W.A. Zajc
Recombination Tested
41

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

17-Oct-03                                                           W.A. Zajc
Second Conclusions
42

   Suppression at high pT is characteristic of dense
matter formation in Au-Au collisions
(lack of suppression for heavy quarks, as observed in N coll
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?

17-Oct-03                                                                      W.A. Zajc
43

Results on Particle Composition

BRAHMS: 10% central
PHOBOS: 10%
PHENIX: 5%
STAR: 5%

200 GeV/A Au+Au

Just a sample!
There are also results on spectra of 0„s, K* ,  , L , LXX , …

17-Oct-03                                                                          W.A. Zajc
Longitudinal Dynamics
44

    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

17-Oct-03                                         W.A. Zajc
45

Is there a „Temperature‟?
    Apparently:
    Assume distributions described by one temperature T and

one ( baryon) chemical potential  :      dn ~ e ( E μ) / T d 3 p

One ratio (e.g., p / p ) determines  / T :                      p e  ( E μ ) / T

 ( E μ) / T  e 2μ / T
STAR preliminary    Systematic errors ~10-20%                           p e

Ratio (chemical fit)
130 GeV RHIC : STAR / PHENIX /
PHOBOS / BRAHMS                                        Central
17.4 GeV SPS : NA44, WA97                                              BRAHMS
PHENIX
PHOBOS
STAR

K/h
p/   K0s/h
K0/h

Model:N.Xu and M.Kaneta
X/h      nucl-ex/0104021
    A second ratio (e.g., K /  ) provides T                               X/h
   Then predict all other hadronic yields and ratios:                                         Ratio (data)
17-Oct-03                                                                                                            W.A. Zajc
Locating RHIC on Phase Diagram
46

Previous figure  RHIC has net baryon density ~ 0:
STAR preliminary Systematic errors ~10-20%
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

RHIC is as
close as
we‟ll get to
the early
universe for
some time

17-Oct-03                                                                W.A. Zajc
Questions
47

   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 

 The first round of RHIC experiments have determined
~all of these parameters (and more)

17-Oct-03                                                               W.A. Zajc
Open Questions
48

   Is the quark-gluon plasma being formed in RHIC
collisions? To be determined:
   Does charmonium show the expected suppression from
(color) Debye screening?

RHIC

   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) First results now available!
   What are the gluon and sea-quark contributions to
the proton spin? (polarized proton running)

17-Oct-03                                                                          W.A. Zajc
Screening by the QGP
49

(An explicit test of deconfinement) In pictures:

r -->                         r -->                          r -->
V(r)

V(r)

V(r)
QCD potential at
QCD potential at              QCD potential at                high T and
T=0                          high T                     high density

Non-perturbative Vacuum

c              c              c              c              c               c

Perturbative Vacuum                                            Color Screening
Perturbative Vacuum

17-Oct-03                                                                                     W.A. Zajc
Screening by the QGP
50

In first-order finger physics:
   Follow usual derivation of Debye screening


 2  4r  4no e  e / kT  e  e / kT   
1            kT
 4e 2no / kT  2  with D 
2                                    2


 D assumptions:  4e 2 no
Now put in QGP scales and        2
4e 2  g 2 ~ 1
no  3.6T 3  T 3 (Stefan - Boltzman for QGP)
T  200 MeV
1 1
 D              0.4 fm
2 gT
~ D will be dissolved
 Study “onium” bound states

17-Oct-03                                                    W.A. Zajc
51

J/Y Measurements To Date
    p-p results:
   ~comparable
facilities
(especially at low pT)

    Au-Au results:
   A limit only
Run-4

17-Oct-03                                             W.A. Zajc
52

    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
   Repeat “complete” measurements with x10-100 sensitivity

17-Oct-03                                                                            W.A. Zajc
Discovery
53

QCD Publications Versus Time


600

500

Discovery of Top

SPIRES Entries
400

300

“Discovery” of QCD
200

100

0
1970   1975     1980       1985        1990   1995   2000
Year

    “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

17-Oct-03                                                                                                      W.A. Zajc
54

Provocative (non)-Questions
“It’s a Quark-Gluon-Plasma,
Period.”
QGP =PQCD + pQCD + dA
Miklos Gyulassy
Columbia University

Three major discoveries at RHIC
1) Conclusive evidence for PQCD via v2 collective flow of 104 p, K, p
2) Conclusive evidence for pQCD jet quenching in Au+Au at RHIC
3) 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
e(t ~ 0.2 fm / c) : 100 e0
17-Oct-03                                                          W.A. Zajc
55

Open(?) Questions

New York Times 6/19/03
"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."

“If we were sure it was the quark-gluon plasma,
we would have said it was.“, W.A.Zajc.

"Most of us aren't quite ready to make that leap," T. Hemmick said.

“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)

17-Oct-03                                                                        W.A. Zajc
Closed Questions
56


     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?
17-Oct-03                                                 W.A. Zajc
57

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)
17-Oct-03                                                         W.A. Zajc
Other New Effects
58

         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                                                        Central
understand this?
Peripheral
A. Competition
between
Fragmentation
and
Recombination

at the quark level

(next slide)
17-Oct-03                                                               W.A. Zajc
59

Experimental Gauge Theory
   QCD is the only fundamental gauge theory
amenable to experimental study in both
   Weak and strong coupling limits
   Particle and bulk limits

Coupling Constant          Number Limit
Weak         Strong       Particle   Bulk
Gravity                     X            X         
Weak                        X                     X
QED                         X                     
QCD                                              

   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
17-Oct-03                                                                    W.A. Zajc
60

My 3 Part Definition of a QGP
QGP =PQCD + pQCD + dA
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 QCD
1.   e+e- -> q q g        2 ok but not 1
2.   p+p -> pi, K, p     2 ok but not 1
3.   e+A -> jets         2 ok but not 1
4.   Nucleus A           1 ok but not 2
5.   SIS,AGS res. gas    1 ok but not 2
6.   SPS A+A             1 ok but 2~OK but not 3!
17-Oct-03                                                       W.A. Zajc
61

17-Oct-03   W.A. Zajc
62

Below RHIC energies, QCD hydro over-predicts elliptic
flow!
v2(Ecm)           QGP hydro for the FIRST time at RHIC!

CERES            17 AGeV

17 AGeV

CERES/SPS                        dNch / dyd2 x ^   (fm- 2 )

17-Oct-03                                                                        W.A. Zajc
63

Yet Another Luminosity Limited Observable

     New PHENIX Run-2 result on v2 of 0‟s:

     Clearly would
benefit
from Run-4 statistics             PHENIX Preliminary

17-Oct-03                                                          W.A. Zajc

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