Burak Alver, Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Richard Bind

1
Energy and System Size Dependence of Charged
Hadron pT Spectra from CuCu and AuAu at ?sNN
62.4 and 200 GeV
Detector (2005)
Collaboration (2005)
CuCu
All-inclusive count
Run 5
AuAu
Run 4
dAu
Burak Alver, Birger Back, Mark Baker, Maarten
Ballintijn, Donald Barton, Russell Betts, Richard
Bindel, Wit Busza ( Spokesperson ), Zhengwei
Chai, Vasundhara Chetluru, Edmundo García, Tomasz
Gburek, Kristjan Gulbrandsen, Clive Halliwell,
Joshua Hamblen, Ian Harnarine, Conor Henderson,
David Hofman, Richard Hollis, Roman Holynski,
Burt Holzman, Aneta Iordanova, Jay Kane, Piotr
Kulinich, Chia Ming Kuo, Wei Li, Willis Lin,
Steven Manly, Alice Mignerey, Gerrit van
Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski,
Robert Pak, Corey Reed, Eric Richardson,
Christof Roland, Gunther Roland, Joe Sagerer,
Iouri Sedykh, Chadd Smith, Maciej Stankiewicz,
Peter Steinberg, George Stephans, Andrei
Sukhanov, Artur Szostak, Marguerite Belt Tonjes,
Adam Trzupek, Sergei Vaurynovich, Robin Verdier,
Gábor Veres, Peter Walters, Edward Wenger,
Donald Willhelm, Frank Wolfs, Barbara Wosiek,
Krzysztof Wozniak, Shaun Wyngaardt, Bolek
Wyslouch ARGONNE NATIONAL LABORATORY BROOKHAVEN
NATIONAL LABORATORY INSTITUTE OF NUCLEAR PHYSICS
PAN, KRAKOW MASSACHUSETTS INSTITUTE OF
TECHNOLOGY NATIONAL CENTRAL UNIVERSITY,
TAIWAN UNIVERSITY OF ILLINOIS AT
CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF
ROCHESTER
Run 3
AuAu
Run 2
PHOBOS Spectrometer NIM A 499, 603-623 (2003)
Results (hh- spectra)
How do we find tracks?
What is our motivation?

• Tracks Corrected for
• Acceptance
• Efficiency
• Feed-down
• Secondaries
• Ghosts
• Momentum Resolution
• Bin width
• Dead channels

10 cm
70 cm
z
x
PHOBOS preliminary
PHOBOS preliminary
y
Results ( )
Centrality measures
Nuclear Modification Factor
Participants
pp reference data 62.4 GeV ISR SFM,
0.5lt?lt1 200 GeV UA1 -2.5lt?lt2.5 (acceptance
correction with PYTHIA)
Npart/2 A (volume)
Collisions
LA1/3
Ncoll of binary collisions A4/3
PRL 94, 082304 (2005)
Phys. Lett. B578, 297 (2004)
Collisions
versus Npart (62.4 GeV)
versus Npart (200 GeV)
Scaling of Hadron Production
PRL 94, 082304 (2005)
Phys. Lett. B578, 297 (2004)
Phys. Lett. B561, 82 - 92 (2003)
Conclusions
Energy / Centrality Factorization
Energy / Centrality Factorization
In both CuCu and AuAu, the ratio of 200 GeV to
62.4 GeV yields are independent of centrality at
all pT.
PRL 94, 082304 (2005)
PRL 94, 082304 (2005)
Edward Wenger, MIT