Status of the Phobos

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Status of the Phobos experiment at RHIC
http//phobos-srv.chm.bnl.gov/
S.Manly Univ. of Rochester (http//hertz.pas.roche
ster.edu/smanly/) for the Phobos
Collaboration RHIC 2000 Workshop Park City,
Utah March 11-18, 2000
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Phobos Collaboration
ARGONNE NATIONAL LABORATORY Birger Back, Nigel
George, Alan Wuosmaa BROOKHAVEN NATIONAL
LABORATORY Mark Baker, Donald Barton, Alan
Carroll, Stephen Gushue, George Heintzelman,
Louis Remsberg, Peter Steinberg, Andrei
Sukhanov INSTITUTE OF NUCLEAR PHYSICS,
KRAKOWAndrzej Budzanowski, Kazimierz Galuszka,
Jan Godlewski , Jerzy Halik, Roman Holynski,
Jerzy Kotula, Marian Lemler, Jozef Ligocki,
Jerzy Michalowski, Andrzej Olszewski?, Pawel
Sawicki Marek Stodulski, Adam Trzupek, Barbara
Wosiek, Krzysztof Wozniak, Pawel
Zychowski JAGELLONIAN UNIVERSITY, KRAKOWAndrzej
Bialas, Wieslaw Czyz, Kacper Zalewski MASSACHUSETT
S INSTITUTE OF TECHNOLOGYWit Busza, Patrick
Decowski, Kristjan Gulbrandsen, P. Haridas, Piotr
Kulinich, Heinz Pernegger, Miro Plesko, Gunther
Roland, Leslie Rosenberg, Pradeep Sarin, Stephen
Steadman, George Stephans, Gerrit van
Nieuwenhuizen, Carla Vale, Robin Verdier,
Bernard Wadsworth, Bolek Wyslouch NATIONAL
CENTRAL UNIVERSITY, TAIWANYuan-Hann Chang,
Augustine Chen, Willis Lin, JawLuen
Tang UNIVERSITY OF ROCHESTERErik Johnson, Steven
Manly, Robert Pak, Inkyu Park, Yanting Wang,
Frank Wolfs UNIVERSITY OF ILLINOIS AT
CHICAGORussell Betts, Clive Halliwell, Burt
Holzman, Judith Katzy, Wojtek Kucewicz, Don
McLeod, Rachid Nouicer, Michael Reuter UNIVERSITY
OF MARYLANDRichard Baum, Richard Bindel, Edmundo
Garcia-Solis, Alice Mignerey
Spokesperson?Also with Brookhaven National
Laboratory
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spectrometer

• ?4p detector
• measuring charged particle
• multiplicity and d N/dhdf
• multiparticle spectrometer
• covers 1 solid angle
• at midrapidity with
• low Pt threshold and good
• particle identification
• Time-of-flight walls
• Trigger counters

time of flight
multiplicity detectors
magnet
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Primary detector technology
Silicon detector scheme
Silicon strips and pads 300 microns
bias bus
signal lines
metal 2
Dielectric 2
vias
metal 1
Dielectric 1
p Implant
Polysilicon Drain Resistor
n

HV
5
Multiplicity array
h lt 5.3
-3.1 lthlt 3.1
-5.3 lt h
z
-1.13 m
1.13 m
2.35 m
-0.55 m
-5.05 m
-2.35 m
0.55 m
5.04 m

• 85 of 4p covered
• Charged part. multiplicity d2N/dhdj (j is
  azimuthal angle to beam) Dh 0.1 and Dj p/4
• Distinguish multiple hits by the energy
  deposition

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Multiplicity determination (event-by-event)
h
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The vertex detector
-12.5 cm
12.5 cm
11.8 cm
5.6 cm
x
Beam
Vertex detector
z
Octagon multiplicity detector
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Two-arm multiparticle Spectrometer
100 MeV/c
1 GeV/c

• 2 Tesla conventional magnet
• low field region helps with
• pattern recognition
• Particle ID via dE/dx

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Spectrometer performance
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Spectrometer physics

• Pt spectra
• correlations
• phi mass, width
• particle ratios

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magnet
RHIC!!
Danfysik
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Phobos Sensor Production
Vertex and Multiplicity
NCU Taiwan Production Pre-Testing
DHL
MIT and UIC Testing
Spectrometer
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Silicon detector assembly and testing
Hughes 2470-V bonder
Inspection stations
Si detectors mounted on spectrometer
cooling/support frame
Gluing Station
Clean Rooms
Probe Stations
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Trigger Counters
ir
Cherenkov counters (548 cm)
Paddle counters (321 cm)
Cherenkov counters
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Cherenkov counters
Paddle counters
Proud dad
ZDC
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Time-of-flight system
Hamamatsu R5900-00-M4MOD 12 stage multi-anode
PMTs
BC-404 fast plastic from Bicron
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Si Bias
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Event Builder
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Test beams
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Engineering Run - summer 99
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Root/C
Software
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Run Plan

• Detector has been assembled (Dec.-Jan.), gt95
  success rate
• Start current run with setup similar to what we
  had in engineering run
• two week shutdown after machine becomes stable,
  install full (1.5 arms) detector
• second arm modules finished by end of the summer
  

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Phobos physics

• high rate
• large acceptance in eta for multiplicity
  detector
• low Pt acceptance
• use global event characteristics (multiplicity,
  fluctuations in dn/deta) event-by-event as
  criteria to form inclusive samples to study in
  more detail with spectrometer/TOF
• multiplicity (and fluctuations), spectra, phi
  meson, particle correlations

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Preliminary studies at Rochester of sensitivity
to global K/? and ratios
P in GeV/c
Angle in degrees
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A discriminator that uses multiplicity detector
information
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K/pi 12.5
K/pi 3.5
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Studying use of vertex detector to separate
events with fluctuations in kaons vs. baryons
Vtx layer 2
Vtx layer 1
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Preliminary studies on flow reconstruction in the
Phobos multiplicity detector
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• 100 RQMD events at each of 90, 45, 0, -45,-90
  degrees
• Use hit multiplicity in map with granularity
  0.05(?)x0.2(?) and fit coordinate anisotropy
  (integrates over particle species and momenta)
• Offset vertex to avoid area around spectrometer
  holes for initial study
• Can reconstruct reaction plane to approximately
  0.5 radians

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SummaryPhobos is in excellent shape and will
be ready to do physics in year 1! In addition to
the usual Phobos physics program, recent
preliminary studies at Rochester indicate Phobos
may be sensitive to integrated species flow, K/
?, and on an event-by-event basis in
region ?lt3.1. Work is continuing hopefully
with real data soon!!