Transcript Document 7251264

p+p
SPS
RHIC
AGS
e+e-
The Landscape of
the Strong Interaction:
Results from
.
Peter Steinberg
Brookhaven National Laboratory
Nuclear/Particle Physics Seminar
Yale University Physics Department
19 February 2004
Peter Steinberg
PHOBOS
What we do @ RHIC
bang
We collide gold nuclei
at the highest energies
100 GeV x
A nucleons
100 GeV/N x
A nucleons
9 GeV
SPS
9 GeV
2-4 GeV
AGS
2-4 GeV
Peter Steinberg
Quarks & Gluons
are released,
creating a hot & dense
state of matter
QGP
“freezes out”
to hadrons
(& leptons,
& photons)
Quark-Gluon plasma
PHOBOS
National Attention
New York Times coverage of
NATIONAL DESK | January 14, 2004, Wednesday
Tests Suggest Scientists Have
Found Big Bang Goo
By JAMES GLANZ (NYT)
At least three advanced diagnostic tests
suggest that an experiment at the
Brookhaven National Laboratory has
cracked open protons and neutrons like
subatomic eggs to create a primordial form
of matter that last existed when the universe
was roughly one-millionth of a second old,
scientists said here on Tuesday…
Peter Steinberg
PHOBOS
Lattice QCD calculations
Teraflop-scale computers are
used to study equilibrium QCD
on a space-time lattice
Calculations predict
phase transition at Tc
hadrons  quarks & gluons
New degrees of freedom!
Tc  173  15 MeV
 c ~ .7 GeV / fm3
cf. T0 ~ 170 MeV,
(proton) ~ .5 GeV/fm3
(nucleus) ~ .17 GeV/fm3
Peter Steinberg
PHOBOS
Proposed QCD Phase Diagram
Temperature
(Average
Kinetic Energy
per Particle)
Quark
Gluon
Plasma
T=170 MeV
(21012 oK!)
T>0
Hadron Gas
T=0
Peter Steinberg
Nuclei
r0
Neutron
Stars?
Nuclear Density
PHOBOS
QGP Search @ RHIC
PHOBOS
BRAHMS
PHENIX
STAR
Tandem
Peter Steinberg
PHOBOS
PHOBOS 2003
C
B
A
4
1
2
3
Peter Steinberg
1.
2.
3.
4.
Spectrometer
Vertex detector
“Octagon”
“Rings” A,B,C
PHOBOS
PHOBOS Collaboration 2004
Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley,
Richard Bindel, Wit Busza (Spokesperson), Alan Carroll, Zhengwei Chai, Patrick Decowski,
Edmundo Garcia, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen, Stephen Gushue,
Clive Halliwell, Joshua Hamblen, Adam Harrington, Conor Henderson, David Hofman, Richard Hollis,
Roman Hołyński, Burt Holzman, Aneta Iordanova, Erik Johnson, Jay Kane, Nazim Khan, Piotr Kulinich, Chia
Ming Kuo, Willis Lin, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej
Olszewski, Robert Pak, Inkyu Park, Heinz Pernegger, Corey Reed, Michael Ricci,
Christof Roland, Gunther Roland, Joe Sagerer, Iouri Sedykh, Wojtek Skulski, Chadd Smith,
Peter Steinberg, George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek,
Carla Vale, Siarhei Vaurynovich, Robin Verdier, Gábor Veres, Edward Wenger, Frank Wolfs,
Barbara Wosiek, Krzysztof Woźniak, Alan Wuosmaa, Bolek Wysłouch, Jinlong Zhang
ARGONNE NATIONAL LABORATORY
INSTITUTE OF NUCLEAR PHYSICS, KRAKOW
NATIONAL CENTRAL UNIVERSITY, TAIWAN
UNIVERSITY OF MARYLAND
Peter Steinberg
BROOKHAVEN NATIONAL LABORATORY
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
UNIVERSITY OF ILLINOIS AT CHICAGO
UNIVERSITY OF ROCHESTER
PHOBOS
PHOBOS Physics Program
• Broad range of control
variables (“landscape”)
•
•
•
•
Beam Energy
System size
Impact parameter
Pseudorapidity
p+p
d+Au
• Research program
• Particle multiplicities
• Identified particle ratios
• Spectra at high pT
Au+Au
• Focus on Multiplicity
• Analog to entropy
Peter Steinberg
PHOBOS
Multiplicity as a QGP Signal
• 1st-order phase
transition
• Jump in entropy
density (s):
s  n T  T
3
hadrons  QGP
• “Jet quenching”:
energy loss of jets
leads to “additional”
gluons
• Clear effect in
models (HIJING)
Peter Steinberg
PHOBOS
Counting Particles in PHOBOS
f
Signals in the Si for
a single RHIC event!
z
Rings
Octagon
Peter Steinberg
PHOBOS
Angular Distributions in p+p
UA1 900 GeV
PHOBOS p+p Preliminary
q
=0
=1
 is an approximation to
rapidity (y)
1  E  pz 
1
y  ln 

tanh
 z 

2  E  pz 
Peter Steinberg
   ln tan q / 2 
Longitudinal distribution
PHOBOS
Centrality Dependence of d+Au
b
We slice our data
using signals in rings
Data vs. AMPT
Shape Changes!
Let’s integrate over
4p!
PHOBOS Preliminary
Peter Steinberg
PHOBOS
Total Multiplicity vs. Npart
b
d+Au scaled by Npp
vs.
# wounded nucleons
(2 in p+p)
N
d  Au
ch

Peter Steinberg
N part
2
 N chp  p
PHOBOS
Can we build d+Au with p+p?
PHOBOS 200 GeV
Yes
N
d  Au
ch

N part
2
 N chp  p
d+Au & p+p preliminary
Peter Steinberg
PHOBOS
Is Npart Fundamental?
Expectations in d+Au:
“stopping” in d direction
“cascading” in Au direction
Why do they add up to
Npart scaling so robustly?
“Long-range” correlation?
nucl-ex/0311009
Peter Steinberg
PHOBOS
Geometry of Au+Au Collisions
Do we have the
building blocks for
Au+Au collisions?
b
Impact parameter controls:
Number of participants &
Binary Collisions per participant
(some dependence on sNN)
Peter Steinberg
PHOBOS
Estimating Centrality in Au+Au
PHOBOS Data
We only assume signal
is monotonic with Npart
Top 6% in signal
correspond to
top 6% in Npart
Use full MC
calculations
to account for
fluctuations
Peter Steinberg
HIJING MC
PHOBOS
dN/d in Au+Au
dN/d
PHOBOS PRL91 (2003)
130 GeV
19.6 GeV
200 GeV
Most Central



Extensive data set:
3 CMS Energies, Npart from 65 – 340, ||<5.4
Once again, we just integrate over 4p!
Peter Steinberg
PHOBOS
Participant Scaling in Au+Au
N
Au  Au
ch

N part
2
 N ch? ?
Extrapolated
to 4p
PHOBOS Au+Au
nucl-ex/0301017
Peter Steinberg
PHOBOS
Can we build Au+Au with p+p/d+Au?
PHOBOS 200 GeV
N part
2
Fundamental difference
between p+p / d+Au & Au+Au?
N part
2
 N ch? ?
 N chp  p
No!
Au+Au nucl-ex/0301017
d+Au & p+p preliminary
Peter Steinberg
PHOBOS
Nch vs. s in p+p and A+A
Central A+A
PHOBOS nucl-ex/0301017
Particle Data Book (2000)
Peter Steinberg
PHOBOS
Comparisons with
+
e e
Multiparticle hadronic final states:
How do they compare?
q
q
DELPHI 209 GeV
UA1 900 GeV
Thrust axis is a natural way to compare pT & y
Peter Steinberg
PHOBOS
A New Wrinkle
Central A+A
PHOBOS nucl-ex/0301017
Particle Data Book (2000)
Peter Steinberg
PHOBOS
A New Wrinkle
N ch   sA exp( B /  s )
(MLLA pQCD, Mueller 1983)
Central A+A
PHOBOS nucl-ex/0301017
Particle Data Book (2000)
Peter Steinberg
PHOBOS
Au+Au approaches e+eCentral A+A
A+A
e+epp/pp
N
Peter Steinberg
Au  Au
ch

N part
2
N
ee
ch
PHOBOS
Angular Distributions
Peter Steinberg
PHOBOS
Energy Dependence near =0
(dN/dyT )
Peter Steinberg
PHOBOS
More Questions than Answers
1. Why is Npart appropriate?
•
How many participants in e+e-?
2. Why does Au+Au agree with e+e- at
high energies?
•
How does p+p fit in?
3. Why do A+A and e+e- disagree at
lower energies?
Peter Steinberg
PHOBOS
1. Is Npart/2 Appropriate?
A A
e e  p p 
N part / 2


So, by transitivity…
A A
e e 
N part / 2

Peter Steinberg

PHOBOS
2. What about p+p?
• In p+p collisions,
have “leading
particles”
• Flat distribution of
dN
dx F
xF  pz / pzmax
independent of energy
• Only ½ of energy
available for
particle production
s p p  s / 2
Peter Steinberg
PHOBOS
Three Behaviors…
Correct for
leading particles
Peter Steinberg
PHOBOS
…Down to Two
Universality of
particle production?
Peter Steinberg
PHOBOS
Historical Note
Leading particle effect
studied at ISR p+p
by comparison to e+e(Basile et al, 1981-1984)
Peter Steinberg
PHOBOS
Why is A+A already like
+
e e?
• Leading particle effect is reduced
• Presumably by multiple collisions
• In PHOBOS result, at least 3 per participant
d+Au dominated by
singly-struck nucleons
Peter Steinberg
PHOBOS
3. Why does A+A “approach”
+
e e
A+A p+p e+e-
Peter Steinberg
PHOBOS
Thermal-Statistical Model
Pioneered by R. Hagedorn, 1963
1500
Grand Canonical Relativistic Gas
Ni  giV 
1000
Mass
(MeV)
r,w
fo

500
d3 p
 2p 
1
3
e
( p 2  m2   B ) / T
1
K
Hadron
Mass Spectrum
p
i  p , K , p, p, , , , , ,
0
0
10
20
30
40
Degeneracy
RHIC
appears to be
in chemical
equilibrium
at T~170 MeV
& B ~ 41 MeV!
Figure from P. Braun-Munziger, D. Magestro, J. Stachel
Peter Steinberg
PHOBOS
Phase Diagram
3. Resonance gas, baryons &
anti-baryons equal
Kaneta & Xu
e+e- & pp?
(Beccatini ‘95)
High energy
Low energy
2. Increase available energy
(increases T, lowers B)
Energy
~ mp
Particle
1. Nucleus is a drop of
baryon liquid @ T=0
(Cleymans & Redlich 1998)
Peter Steinberg
PHOBOS
Statistical Models and
+
e e /pp
F. Becattini, hep-ph/9701275
Statistical models also describe e+e- and p+p:
• “Temperature” ~ constant vs. s
• Typically B assumed to be ~0
Peter Steinberg
PHOBOS
Relating A+A and
+
e e
Vee(s)
Thermal
Models
can
calculate
entropy
density
N chee  s To ,0 Vee  soVee
N
A A
ch
 N part

 2
A A
ch
ee
ch
2 N
N part N
Experimental
Peter Steinberg
VAA
VAA (s)

 s T ,  B VAA

VAA
VAA
s T ,  B 
VAA s  T ,  B 



Vee
so V  V
so
ee
Assumption!
AA
Theoretical
PHOBOS
Entropy Density vs. Beam Energy
s T , B 
J. Cleymans & M. Stankiewicz
University of Cape Town
so
Evaluated along
freezeout contour
 a

s  b
 1
 B

Ts    p   B n
s
Peter Steinberg
PHOBOS
Comparison with Data
s T ,  B 
so
N
Peter Steinberg
Qualititative
agreement
N
Au  Au
ch
 ee
B 

  N ch  

V2ee ~ VAA
T 
part
PHOBOS
Universality of Strong Interaction
• So it seems as if
• Separating wounded baryons (participants)
y
• Produce same number of particles (and ~dN/d)
as separating quarks with same available energy
Not a new concept,
even in gauge theories
Brodsky & Gunion (1976)
• Unless there are initial baryons to conserve!
Peter Steinberg
PHOBOS
What Now?
• Interesting phenomenology  will it work @ LHC?
HIJING is
x2 higher!
Peter Steinberg
JETSET
PHOBOS
What About the QGP?
Nch
Npart
Was the QGP
created at RHIC?
N
Au  Au
ch
N part  ee
B 

  Nch  

2
T 

Constraint on entropy  Constraint on Dynamics
Peter Steinberg
PHOBOS
We need a physical scenario that builds in:
Entropy creation & conservation
Thermal/Statistical Phenomenology
Peter Steinberg
PHOBOS
Landau Hydrodynamics
Thermal spectra
Landau considered
strong interactions as
complete stopping
of Lorentz-contracted
pancakes
…in 1953
Universal
Entropy
per Npart/2:
Isentropic,
scale-free
hydro
S~s1/4
  T   0
Landau, Carruthers, Cooper/Frye, …
P. Steinberg (BNL), G. Roland (QM04)
Peter Steinberg
p  /3

s
 2m p
s y2  ln 

  ln  

T~mp
Gaussian dN/dy
BRAHMS
prel.
s ~ 2.3
s y ~ 2.2
PHOBOS
Conclusions
• PHOBOS is an excellent detector to survey the
landscape of strong interactions
• p+p, d+Au, Au+Au (energies, centralities)
• Energy and species scan still to come!
• Nch reveals connections between Au+Au and
elementary reactions (p+p, e+e-) in conjunction
with thermal (& hydrodynamic) approaches
• Npart scaling, Universal multiplicity, B effect
• Counterintuitive, but apparently useful
• Consolidates understanding of strong interaction
• A “map” for understanding nuclear dynamics from AGS
through RHIC & LHC!
Peter Steinberg
PHOBOS
.
p+p
SPS
RHIC
AGS
e+e-
Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley,
Richard Bindel, Wit Busza (Spokesperson), Alan Carroll, Zhengwei Chai, Patrick Decowski,
Edmundo Garcia, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen, Stephen Gushue,
Clive Halliwell, Joshua Hamblen, Adam Harrington, Conor Henderson, David Hofman, Richard
Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Erik Johnson, Jay Kane, Nazim Khan,
Piotr Kulinich, Chia Ming Kuo, Willis Lin, Steven Manly, Alice Mignerey, Gerrit van
Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Inkyu Park, Heinz Pernegger,
Corey Reed, Michael Ricci, Christof Roland, Gunther Roland, Joe Sagerer, Iouri Sedykh,
Wojtek Skulski, Chadd Smith, Peter Steinberg, George Stephans, Andrei Sukhanov, Marguerite
Belt Tonjes, Adam Trzupek, Carla Vale, Siarhei Vaurynovich, Robin Verdier, Gábor Veres,
Edward Wenger, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Alan Wuosmaa, Bolek
Wysłouch, Jinlong Zhang
Peter Steinberg
PHOBOS
Gaussian Rapidity Distributions
E895
E895
E895
NA49
NA49
BRAHMS
prel.
Shown by G. Roland, QM04
Peter Steinberg
PHOBOS
Jet Quenching & Entropy
Suppression of high-pT
particles indicates
parton energy loss
~Npart scaling 
Surface emission
Absorbed jets must
radiate. Where is
this “extra” entropy?
Peter Steinberg
PHOBOS
Quarks & Gluons
Quarks are the “matter”
in everyday matter
Gluons are like “charged” photons
u c t
up
charm
top
d s b
down
strange
“QED”
(qqg)
Non-Abelian Terms
(ggg & gggg)
bottom
u
“QCD”
Quantum Chromodynamics
Field theory describing
interactions of quarks &gluons
Peter Steinberg
d
“EASY”
(perturbative QCD)
u
“HARD”
(non-perturative)
PHOBOS
p
Bound States of QCD
Instead, we see colorless
bound states  “hadrons”
No-one has ever seen a quark.
QCD is a “confining” gauge theory,
with an effective potential:
4 s
V 
 kr
3 r
“Coulomb”
“Coulomb”
“Confining”
“Confining”
V(r)
p
u
p
u
d
mp = 938 MeV

u
d
s
Ss
u
u
mp = 135 MeV
K
u
s
mK = 495 MeV
m = 1115 MeV
r
Peter Steinberg
We do not yet
understand these
masses (or their spins!)
by using pQCD!
PHOBOS
Strong Thermodynamics
Hadron 'level' diagram
Density of States vs Energy
1500
r M 
250
T0 ~ 170MeV
200
1000
Mass
(MeV)
Number of 150
available
states 100
r,w
fo

500
K
50
p
0
0
0
10
20
30
Degeneracy
40
0
500
1000
1500
2000
Mass (MeV)
Hagedorn (1963)
r  m ~ m e
a m / T0
 Z   r  m  e m / T dm   T  T0 
Suggestive of a phase transition, even w/ no dynamical details!
Figures from
W. Zajc, Columbia University
Peter Steinberg
PHOBOS
The Bulk of Particles @ RHIC
Peter Steinberg
PHOBOS
Strong “Blackbody” Radiation
PHOBOS Central (head-on) Au+Au 200 GeV
(Transverse momentum)
Peter Steinberg
PHOBOS
RHIC Experiments (to scale)
PHENIX
BRAHMS
STAR
PHOBOS
Two BIG Spectrometers:
100’s-1000’s particles event
Particle ID, photons & leptons
Peter Steinberg
Two small detectors:
Forward particles,
Particle multiplicity
PHOBOS
2-jet Events in
Peter Steinberg
+
e e
PHOBOS
What happened to leading particles?
• BRAHMS measured net protons vs. y @ 200 GeV
• Baryons not fully stopped at 200 GeV: Ep/Ebeam ~ 28±6%
nucl-ex/0312023
• Why does Au+Au seem to get the whole s?
Peter Steinberg
PHOBOS
Hint: Leading Particles in
+
e e
• What fraction of beam energy does fastest particle
in e+e- get?
PYTHIA 6.205/JETSET 7.3
ee
Emax
~ 0.26
Ebeam
• BRAHMS estimates
AA
Enet
p
Ebeam
~ 0.28
• Neither e+e- nor A+A
are fully “stopped”
Peter Steinberg
PHOBOS
Non-Universality?
Details show
differences between
kinematic quantites
vs. s
(4p)
(=0)
Again, only claim
is that entropy
is universal
These differences
may illuminate the
essential differences
(e.g. transverse size,
fluctuations)
Peter Steinberg
PHOBOS
Predictions at =0
Peter Steinberg
PHOBOS