Scaling Properties in Heavy Ion Collisions

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Scaling Properties in Heavy Ion Collisions
Nigel George BNL For the Collaboration
AGS/RHIC Users Meeting September 20-21, 2002, BNL
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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
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The PHOBOS Detector (2001)
137000 Silicon Pad Channels
Spectrometer
1m
Ring Counters
Octagon
Nearly 4p Coverage
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QGP Signatures and Scaling with System Size and
Energy

• QGP signatures/diagnostics
• Strangeness enhancement
• Entropy production
• J/psi suppression
• Jet quenching
• Scaling violations relative to
• Reference (e.g. pp, pA)
• Scaling assumption (Npart, Ncoll)
• Study scaling properties for
• Bulk particle production
• High pT hadrons

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Systematic level arm
Over centrality range
Over energy range
65
20
200 GeV
355
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PHOBOS Data on dN/dh in AuAu vs Centrality and ?s
200 GeV
19.6 GeV
130 GeV
PHOBOS
PHOBOS
PHOBOS
dN/dh
Typical systematic band
(90C.L.)
h
Extensive systematic multiplicity data set
Fragmentation region
dN/dh _at_ h 0
Integral ltNChgt
h 0
h ybeam
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Energy dependence of dN/dh shape
PHOBOS AuAu
dNch/dh
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Universal Limiting Curve in AA fragmentation
region
19.6 data allows extrapolation to extract Nch
Significant particle production in AA
fragmentation region
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Total Charged Multiplicity
Systematic errors not shown
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Physical relevance of the slope?
Systematic errors not shown
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Need to consider leading particle effect in pp
Measured by Basile et al (1980-1984)
?s
?seff
pQCD ee- Calculation
(A. Mueller, 1983)
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Comparison ltNChgt vs. Energy
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Comparison ltNChgt vs. Energy
PHOBOS Central AuAu
ee-
ee-
pp (pp) data _at_ ?seff
Central AA
Different systems converge at high
energy. Universality of Nch?
1 10 102 103
?s (GeV)
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AA and ee- _at_ 200GeV similar in shape
200 GeV
ee- measures dN/dyT(rapidity relative
tothrust axis)
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Particle density near midrapidity
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Results Limiting Fragmentation vs Centrality
Centrality dependence dNch/dh

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

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Mid-rapidity multiplicity dependence on Npart
Preliminary
Systematic errors not shown
dN/dh varies from Npart scaling
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PT distribution of charged particles
Phobos Preliminary
Soft part of spectrum
Systematic Errors not shown
What about high pt?
Hard part of spectrum
Different regime from measurements ..
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Pt dependence of yields at midrapidity (y0.8)
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Centrality dependence in the low pT regime
Charged particle mid-rapidity density
Phobos Preliminary
Phobos Preliminary
Centrality dependence of spectra
consistent with charged particle dependence
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Npart scaling in the high pt regime
Phobos Preliminary
Phobos Preliminary
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Npart Scaling at high pT
PHOBOS Preliminary
Ncoll-scaling
Normalized to yield at Npart 65

• Npart scaling describes data at pT 4.25 GeV/c

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Summary

• Universal limiting curve for particle
  production - No broad boost-invariant region
• Total particle production scales with Npart
• - High pt production also scales with Npart
• Universality of energy dependence of ltNChgt in
  ee-,pp,AA collisions
• - Similarity of dN/dh in AA and ee- at high
  energies