Marguerite Belt Tonjes,

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Results From the Experiment at RHIC

• Marguerite Belt Tonjes,
• U. Maryland group at Brookhaven National Lab
• for the Phobos Collaboration

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Collaboration (May 2003)
Birger Back, Mark Baker, Maarten Ballintijn,
Donald Barton, Bruce Becker, Russell Betts,
Abigail Bickley, Richard Bindel, Andrzej
Budzanowski, Wit Busza (Spokesperson), Alan
Carroll, 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 Holynski,
Burt Holzman, Aneta Iordanova, Erik Johnson, Jay
Kane, Nazim Khan, Piotr Kulinich, Chia Ming Kuo,
Jang Woo Lee, Willis Lin, Steven Manly, Alice
Mignerey, Gerrit van Nieuwenhuizen, Aaron Noell,
Rachid Nouicer, Andrzej Olszewski, Robert Pak,
Inkyu Park, Heinz Pernegger, Corey Reed, Louis
Remsberg, Christof Roland, Gunther Roland, Joe
Sagerer, Pradeep Sarin, Pawel Sawicki, Iouri
Sedykh, Wojtek Skulski, Chadd Smith, Peter
Steinberg, George Stephans, Andrei Sukhanov, Ray
Teng, Marguerite Belt Tonjes, Adam Trzupek,
Carla Vale, Robin Verdier, Gábor Veres, Bernard
Wadsworth, Frank Wolfs, Barbara Wosiek,
Krzysztof Wozniak, Alan Wuosmaa, Bolek Wyslouch,
Jinlong Zhang ARGONNE
NATIONAL LABORATORY BROOKHAVEN NATIONAL
LABORATORY INSTITUTE OF NUCLEAR PHYSICS, KRAKOW
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
NATIONAL CENTRAL UNIVERSITY, TAIWAN
UNIVERSITY OF ILLINOIS AT CHICAGO
UNIVERSITY OF MARYLAND
UNIVERSITY OF ROCHESTER
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Experiment 2002
f
0
3
-3
-5.4
5.4
h
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Measurements of Interest

• Bulk particle properties
• Compare to ee-, pp, pA reference
• Properties of hadrons at high pT
• Ncoll, Npart system dependence
• scaling violations jet quenching...

Ncoll NN collisions a A4/3
Npart/2 participating nucleon pairs a A
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PHOBOS Data, dN/dh in AuAu(Centrality and vs)
200 GeV
19.6 GeV
130 GeV
more central
PHOBOS
PHOBOS
PHOBOS
dN/d?
Typical systematic band
(90C.L.)
Phys. Rev. Lett. (2003), in press
h
h
h
? Extensive systematic multiplicity data set
Fragmentation region
dN/dh _at_ h 0
Integral ltNChgt
h 0
h ybeam
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ltNchgt/ltNpart/2gt vs. Energy
AuAu
ee- calculation
(A. Mueller, 1983)
nucl-ex/0301017 Submitted to Phys Rev Lett
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Comparison to ee- Fit
ee-
PHOBOS Central AuAu
ee-
pp (pp) data _at_ vseff
SPS
ltNchgt (ltNchgt/ltNpartgt/2)/ ee- Fit
Central AA
Different systems converge at high
energy. Universality of Nch?
AGS
1 10 102 103
vs (GeV)
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Examine pT Distribution of Charged Particles
AuAu
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 Spectra for AuAu
Npart
Centrality
65 4
45-50
93 5
35-45
138 6
25-35
200 8
15-25
276 9
6-15
344 12
0-6
Centrality range ltbgt from 10 to 3 fm
0.2ltyp lt1.4
nucl-ex/0302015 Submitted to Phys Lett B
Does Npart scaling work at high pt?
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Comparison of AuAu and pp Spectra at 200 GeV

• We observe a significant change in the spectral
  shape between pp and AuAu collisions even for
  mid-peripheral events
• There is a clear suppression of Ncoll scaling at
  high pT
• Causes?
• initial state already in Au wave function
• final state effects

nucl-ex/0302015 Submitted to Phys Lett B
pp from UA1 Nucl.Phys.B335, (1990) 261
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Phobos dAu Preliminary
Transverse Momentum Distributions in dAu
Centrality Determination
0 20
0.2lthlt1.4
3.0lthlt5.4
20 40
PHOBOS dAu preliminary
40 70
Counts
70 100
Energy (arb. units )
Central
Peripheral
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Phobos Preliminary dAu Results
6 central
pp from UA1 Nucl.Phys.B335, (1990) 261
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Summary

• Comprehensive set of dN/dh (-5.3 h 5.3)
  measurements over a broad range of vs (19.6, 130,
  200 GeV), and centrality
• ltNchgt/(ltNpartgt/2) at high energies is the same
  for AuAu and ee-
• Central AuAu collisions show a strong violation
  of collision scaling at high pT
• Preliminary dAu spectra show a qualitative
  difference from AuAu
• This implies that scaling in central AuAu
  collisions is due to final state effects . . . ?
• dAu spectra paper submitted tomorrow
• In progress . . .
• dAu pp identified particle ratios, spectra,
  multiplicity

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Extra slides
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Experiment2003

• Moved TOF walls to 5m from interaction point
• New spectrometer trigger selects high pT tracks
• New T0 Cerenkov detectors for triggering, online
  vertexing, and as a start time for TOF walls
• Proton calorimeter for dA run

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