Mark D. Baker (BNL)

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PHOBOS

• Mark D. Baker (BNL)
• for the PHOBOS collaboration
• August 7, 2000
• RHIC/AGS Users Meeting

dN/dh (h0) for central events Full (1-arm)
detector commissioning
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PHOBOS Collaboration

• ARGONNE NATIONAL LABORATORY
• Birger Back, Nigel George, Alan Wuosmaa
• BROOKHAVEN NATIONAL LABORATORY
• Mark Baker, Donald Barton, Mathew Ceglia, Alan
  Carroll, Stephen Gushue, George Heintzelman,
  Hobie Kraner ,Robert Pak,Louis Remsberg, Joseph
  Scaduto, Peter Steinberg, Andrei Sukhanov
• INSTITUTE OF NUCLEAR PHYSICS, KRAKOW
• Wojciech Bogucki, Andrzej Budzanowski, Tomir
  Coghen, Bojdan Dabrowski, Marian Despet,
  Kazimierz Galuszka, Jan Godlewski , Jerzy Halik,
  Roman Holynski, W. Kita, Jerzy Kotula, Marian
  Lemler, Jozef Ligocki, Jerzy Michalowski, Andrzej
  Olszewski?, Pawel Sawicki , Andrzej Straczek,
  Marek Stodulski, Mieczylsaw Strek, Z. Stopa, Adam
  Trzupek, Barbara Wosiek, Krzysztof Wozniak, Pawel
  Zychowski
• JAGELLONIAN UNIVERSITY, KRAKOW
• Andrzej Bialas, Wieslaw Czyz, Kacper Zalewski
• MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• Wit Busza, Patrick Decowski, Piotr Fita, J.
  Fitch, C. Gomes, Kristjan Gulbrandsen, P.
  Haridas, Conor Henderson, Jay Kane , Judith Katzy
  , Piotr Kulinich, Clyde Law, Johannes
  Muelmenstaedt, Marjory Neal, P. Patel, Heinz
  Pernegger, Miro Plesko, Corey Reed, Christof
  Roland, Gunther Roland, Dale Ross, Leslie
  Rosenberg, John Ryan, Pradeep Sarin, Stephen
  Steadman, George Stephans, Katarzyna Surowiecka,
  Gerrit van Nieuwenhuizen, Carla Vale, Robin
  Verdier, Bernard Wadsworth, Bolek Wyslouch
• NATIONAL CENTRAL UNIVERSITY, TAIWAN
• Yuan-Hann Chang, Augustine Chen, Willis Lin,
  JawLuen Tang
• UNIVERSITY OF ROCHESTER
• A. Hayes, Erik Johnson, Steven Manly, Robert Pak,
  Inkyu Park, Wojtech Skulski, Teng, Frank Wolfs
• UNIVERSITY OF ILLINOIS AT CHICAGO
• Russell Betts, Christopher Conner, Clive
  Halliwell, Rudi Ganz, Richard Hollis, Burt
  Holzman,, Wojtek Kucewicz, Don McLeod, Rachid
  Nouicer, Michael Reuter
• UNIVERSITY OF MARYLAND
• Richard Baum, Richard Bindel, Jing Shea, Edmundo
  Garcia-Solis, Alice Mignerey

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Min. Bias Trigger Event Selection
Positive Paddles
Negative Paddles
ZDC N
ZDC P
Au
Au
PN
PP

• We attempt to trigger on ALL collisions.
• Good paddle timing.
• Good ZDC timing OR Large paddle signal.

3lthlt4.5
h
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ZDC Sum vs. Paddle Sum
130 AGeV
central
peripheral
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Estimating Npart
Events/bin
Npart

• 6 most central events based on paddles gives

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What do we learn from dNch/dh hlt1 ?

• Its a fundamental handle on the initial state
• Proportional to energy density
• Proportional to entropy density
• Proportional to initial gluon density
• It constrains models, especially when energy and
  centrality systematics are included.

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Commissioning Run Setup
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Tracklets
2 hits vertex
Si
Si
beampipe
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dN/dh for hlt1
56 AGeV 4081230
130 AGeV 5551235
Submitted to PRL hep-ex/0007036
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Constraining the Models
X.N.Wang et al.
PHOBOS
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Silicon Detectors
Partially assembled Octagon
Ring arrays
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More Silicon Detectors
Spectrometer
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PHOBOS Apparatus
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Full Detector Event
100,000 channels
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Octagon Unrolled
VTX
f
VTX
Z
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Plans Conclusions

• dN/dhh0 measured for central events.
• Full detector installed.
• Looks healthy.
• Hit processing, alignment, tracking
• Physics Plans
• dN/dh
• Centrality dependence
• Shape over full h range.
• Spectrometer physics (ratios, HBT, spectra)