Global Observations from PHOBOS

1
Global Observations from PHOBOS
Mark D. Baker Brookhaven National Laboratory
for the Collaboration Quark
Matter 2002 July 18-24, 2002, Nantes
2
Collaboration
ARGONNE NATIONAL LABORATORY Birger Back, Alan
Wuosmaa BROOKHAVEN NATIONAL LABORATORY Mark
Baker, Donald Barton, Alan Carroll, Nigel George,
Stephen Gushue, George Heintzelman, Burt
Holzman, Robert Pak, Louis Remsberg, Peter
Steinberg, Andrei Sukhanov INSTITUTE OF NUCLEAR
PHYSICS, KRAKOW Andrzej Budzanowski, Roman
Holynski, Jerzy Michalowski, Andrzej Olszewski,
Pawel Sawicki, Marek Stodulski, Adam Trzupek,
Barbara Wosiek, Krzysztof Wozniak MASSACHUSETTS
INSTITUTE OF TECHNOLOGY Maartin Ballintijn, Wit
Busza (Spokesperson), Patrick Decowski, Kristjan
Gulbrandsen, Conor Henderson, Jay Kane, Judith
Katzy, Piotr Kulinich, Jang Woo Lee, Heinz
Pernegger, Corey Reed, Christof Roland, Gunther
Roland, Leslie Rosenberg, Pradeep Sarin,
Stephen Steadman, George Stephans, Carla Vale,
Gerrit van Nieuwenhuizen, Gábor Veres, Robin
Verdier, Bernard Wadsworth, Bolek
Wyslouch NATIONAL CENTRAL UNIVERSITY,
TAIWAN Chia Ming Kuo, Willis Lin, Jaw-Luen
Tang UNIVERSITY OF ILLINOIS AT CHICAGO Russell
Betts, Edmundo García, Clive Halliwell, David
Hofman, Richard Hollis, Aneta Iordanova, Wojtek
Kucewicz, Don McLeod, Rachid Nouicer, Michael
Reuter, Joe Sagerer UNIVERSITY OF
MARYLAND Abigail Bickley, Richard Bindel, Alice
Mignerey, Marguerite Belt Tonjes UNIVERSITY
OF ROCHESTER Joshua Hamblen, Erik Johnson, Nazim
Khan, Steven Manly, Inkyu Park, Wojtek
Skulski, Ray Teng, Frank Wolfs
3
The PHOBOS Detector (2001)
Spectrometer
Vertex
1m
Octagon
Paddle Trigger Counter
Ring Counters
Cerenkov Counter
137000 Silicon Pad Channels
ZDC
ZDC
DX magnet
DX Magnet
12m Be Beampipe
4
Hits and Tracks in PHOBOS
Nearly 4p Coverage
Spectrometer
p
PID
f
K
?
0
3
-3
5.4
-5.4
h
Distribution of hits and energy deposition ? dN/dh
5
PHOBOS _at_ QM2002 Physics Topics

• Charged Particle Multiplicities
• P. Steinberg Thursday 18th, 1430 Session I
• Flow and HBT
• S. Manly Thursday 18th, 1430 Session II
• Identified Particles
• B. Wosiek Friday 19th, 1430 Session I
• High pT Hadrons
• C. Roland Saturday 20th, 1430 Session I

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PHOBOS Data on dN/dh in AuAuvs Centrality and ?s
200 GeV
19.6 GeV
130 GeV
PHOBOS
PHOBOS
PHOBOS
Preliminary
dN/dh
Typical systematic band
(90C.L.)
h
h
h
Extensive systematic multiplicity data set
7
v2 vs h and ?s
Averaged over Centrality
PHOBOS AuAu
nucl-ex/0205021
200 GeV
130 GeV
From talk by S. Manly
8
Charged Hadron Spectra out to High pT
See talk by Christof Roland
9
v2 vs pT (200 GeV)
0 lt h lt 1.5
200 GeV AuAu
v2
Averaged over centrality
PHOBOS preliminary
pT (GeV/c)
10
Yields at Low pT (AuAu _at_ 200 GeV)
15 central -0.1lt y lt0.4
p p -
K K-
1/(2?pT) d2N/dydpT
p p
PHOBOS preliminary
See talk by Barbara Wosiek
pT (GeV/c)
11

• Broad range systematic dataset
• AuAu at ?s19.6, (56), 130, 200 GeV
• d2N/dhdf over 11 units of h, 2p in f
• d2N/dpTdy up to a pT of 5 GeV/c
• Global Observations
• Empirical Scaling Rules

12
Energy Dependence of Central dN/dh
Scale by Npart/2 shift to hh- ybeam
PHOBOS AuAu
dNch/dh
dNch/dh /ltNpartgt
6 central
PHOBOS AuAu
19.6 GeV is preliminary
19.6 GeV is preliminary
Systematic errors not shown
The fragmentation region extent grows with ?sNN
13
Rule 1 Universal Limiting Curve for Particle
Production
UA5, Z.Phys.C33, 1 (1986)
p p inel.
dNch/dh /ltNpartgt
6 central
dN/dh
PHOBOS AuAu
19.6 GeV is preliminary
Systematic errors not shown
14
Total Multiplicity for AA and pp (pp)
AA data is central
19.6 GeV is preliminary
15
Remove the Leading Proton Effect
?s
?seff
Basile et al (1980-1984)
pQCD ee- Calculation
(A. Mueller, 1983)
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Comparison of áNchñ vs. Energy
pQCD ee- Calculation
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Comparison of áNchñ vs. Energy
PHOBOS Preliminary Central AuAu
ee-
pp (pp) data _at_ ?seff
Central AA

• Different systems converge
• at high energy.
• Universality of Nch?

1 10 102 103
?s (GeV)
From talk by P. Steinberg
18
Rule 2 Similarity of AA and ee-at High Energy
200 GeV
ee- measures dN/dyT(rapidity relative
tothrust axis)
19
Centrality Dependence at Mid-rapidity
PHOBOS AuAu
200 GeV
PRC 65 (2002) 061901R
130 GeV
19.6 GeV preliminary
See Aneta Iordanovas Poster
20
?Nch? scales with Npart
Error bands due to high-h extrapolation
AuAu
(preliminary)
Total charged particle production Npart
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Results Limiting Fragmentation vs Centrality
Centrality dependence dNch/dh

• Shape changes with centrality
• Full integral changes very little with centrality

PHOBOS AuAu
0-3 central
35-40 central
200 GeV
19.6 GeV preliminary
Systematic errors not shown
22
Charged Hadron Spectra

• Normalize by ltNpartgt/2
• Divide by the value at Npart65

23
Normalize by Npart/2. Divide by the value at
Npart65
Collision scaling would imply
PHOBOS Preliminary
AuAu 200 GeV
UA1 pp (200 GeV)
Rule 3 Particle Production Scales with Npart
See Christof Rolands talk
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Global Observations for AA Particle Production

• Broad, systematic dataset
• Empirical Scaling Rules
• Universal Limiting Curve for Particle Production
• No broad boost-invariant region
• Similarity of AA and ee- at High Energy
• Particle production scales with Npart
• Even at pT of 4-5 GeV/c!

25
Backup slides
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Many ways to slice pz
Rapidity Generalized velocity
Feynman x scaled pz
Pseudorapidity y easier to measure
Away from mid-rapidity
27
Universal Behaviorof Charged Particle
Multiplicitiesin Heavy-Ion Collisions

• Peter Steinberg
• Brookhaven National Laboratory
• for the PHOBOS Collaboration
• Quark Matter 2002
• July 18-24, 2002, Nantes

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Rapidity Distributions at 200 GeV
q
q
200 GeV Central AuAu
ee- measures dN/dyT(rapidity relative
tothrust axis)
yT
h
AA/pp 1.4-1.5
Surprising agreement in shape between AA/ee- /pp
Correspondence between perturbative and
non-perturbative approaches?
29
Particle density near midrapidity
30
Total Multiplicity vs. Beam Energy
Central AA
31
How can AA scale like ee-?
E910
pA collisions
NA49
n counts collisions Npartn1

• With increasing n
• Proton stops (i.e. deposits energy)
• Pion yield saturates

• Above n3, pion yields constant
• Central AA has n5-6 per participant
• Scaling with Npart
• Reduces leading particle effect
• Scaling with ?s

32
Centrality Dependence of ?Nch?
Error band due to high-h extrapolation
sinel42 mb (RHIC)
AuAu
sinel33 mb (SPS)
sinel21 mb (AGS)
Glauber Monte Carlo
19.6 GeV Preliminary
The Return of the Wounded Nucleon Model
Bialas Czyz 1976, Elias et al 1978
33
Scaling of Charged Hadron pT distributions in
AuAu collisions at 200 GeV
Christof Roland MIT for the PHOBOS
Collaboration Quark Matter 2002 July 18-24,
2002, Nantes
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Spectrometer Performance
Acceptance
Momentum Resolution

• Data Sample Production Run 2001(200 GeV)
• 7.8 M AuAu Events, Min. Bias Trigger
• 32 M reconstructed particles

35
PHOBOS-Spectra _at_ 200GeV

• Spectra corrected for
• Acceptance/Efficiency
• Ghost Tracks
• Momentum resolution
• Variable bin width
• Secondaries
• At 200GeV min. bias. pp reference data exists

_
0.2ltyp lt1.4
36
Scaled Spectra / pp-Fit
_
PHOBOS Preliminary

• Centrality range
• ltbgt from 10 to 3 fm
• ltngt from 3 to 6

37
Centrality scaling in pT bins
Relative Yield
Npart
Spectra normalized to yield at Npart 65
38
Comparison to Lower Energies

• Data taken at 130GeV shows similar trends
• Shape is consistent with measurements by STAR

Relative Yield
39
Number of collisions at different Energies
40
Integrated Yields vs Centrality
dN/dy Spectra Integral
dN/dh - Multiplicity data
41
Mean pT vs centrality
42
Centrality scaling in pT bins
Relative Yield
Npart
Spectra normalized to FIT to yield at Npart 65
43
Evolution with Centrality
PHOBOS

• Follow change of shape vs most peripheral bin.

44
Triggering on Interactions
Positive Paddles
Negative Paddles
ZDC N
ZDC P
Au
Au
PN
PP

• Coincidence between
• Paddle counters
• Paddle ZDC timing reject background

Valid Collision
45
Centrality Determination
Data
HIJING GEANT Glauber calculation Model of
paddle trigger
Paddle signal
DataMC
Nparticipants
46
Flow and Bose-Einstein Correlations in Au-Au
Collisions at RHIC
Steven Manly (Univ. of Rochester) For the
PHOBOS Collaboration
Flow constitutes the bulk of this talk
Probe the source dynamics through correlations
47
Flow Hit-based method
nucl-ex/0205021 submitted to PRL
48
Flow Hit-based method
nucl-ex/0205021 submitted to PRL
Select vertices offset in Z, symmetric coverage
in ?, ?
49
Flow Hit-based method
nucl-ex/0205021 submitted to PRL
Select vertices offset in Z, symmetric coverage
in ?, ?
Reaction plane determined by subevents in -2lt?lt2
50
Flow Track-based
New for QM2002!
51
Flow Track-based
New for QM2002!
Reaction plane determined by hits in widely
separated subevent regions, symmetric in ?, ?
52
Hit-based analysis
Track-based analysis

• pt dependence
• Tracks less background sensitive
• Minimal MC dependence
• Subevents and tracks wwwidely separated in h
• (Species dependence)

• Large h coverage
• Event-by-event
• Uniform acceptance in ?
• Separated subevents

53
v2 vs. centrality and energy
hlt1
v2
200
130
PHOBOS Au-Au
Hit-based result v2200 v2130 similar
ltNpartgt
130 GeV result nucl-ex/0205021, submitted to PRL

54
v2 vs. centrality, method comparison
v2
hlt1
v2200 (hit)
v2200 (track)
track
hit
PHOBOS Preliminary 200 GeV Au-Au
ltNpartgt
Hit and track-based results agree!
55
Identified Particles in AuAu Collisions at ?sNN
200 GeV
Barbara Wosiek Institute of Nuclear Physics,
Kraków, Poland for the
Collaboration
56
pT measurements with the
spectrometer
Z
dN/dpT
near mid-rapidity
up to 5 GeV/c
0.03 0.2 1.0
pT, GeV/c
Charge
PID
Mass Charge
Mass
This talk Christof Rolands
talk, Sat.
57
?sNN 200 GeV Comparison to models
HIJING RQMD HYDROTHERMAL W.Broniowski,W.Florkow
ski (PRL87,2001,272302PRC65,2002,064905)
AuAu yields scaled by 1/ltNpart/2gt
(???)
(KK)
(pp)
10
10
10
1
1
1
1/ (2?mT) d2N/dydmT 1/ltNpart/2gt
10-1
10-1
10-1
PHOBOS preliminary
PHOBOS preliminary
PHOBOS preliminary
10-1
10-2
10-1
10-2
10-1
10-2
1
1
1
mT m0
PHENIX 130 GeV PRL88,2002,242301
(pp) corrected for feeddown

• very low pT
• (pp) models differ by a factor 2 to 6