Transcript THE PHOBOS EXPERIMENT AT RHIC Judith Katzy for the

THE PHOBOS EXPERIMENT
AT RHIC
Judith Katzy
for the
PHOBOS Collaboration
PHOBOS Collaboration
ARGONNE NATIONAL LABORATORY
Birger Back, Russell Betts, Alan Wuosmaa
, Nigel George
BROOKHAVEN NATIONAL LABORATORY
Mark D.Baker, Donald Barton, Alan Carroll, Stephen Gushue, George Heintzelman, Louis Remsberg,
Andrei Sukhanov
INSTITUTE OF NUCLEAR PHYSICS, KRAKOW
Wojciech Bogucki , Andrzej Budzanowski, Tomir Coghen, Kazimierz Galuszka, Jan Godlewski ,Roman
Holynski,
Jerzy Kotula, Marian Lemler, Jerzy Michalowski, Andrzej Olszewski, Pawel Sawicki
Marek Stodulski, 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, 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, TAIWAN
Yuan-Hann Chang, Augustine Chen, Willis Lin
UNIVERSITY OF ROCHESTER
Adam Hayes, Erik Johnson, Steven Manly, Robert Pak, Inkyu Park, Frank Wolfs
UNIVERSITY OF ILLINOIS AT CHICAGO
Russell Betts, Clive Halliwell, Burt Holzman, Judith Katzy, Wojtek Kucewicz,
Don McLeod, Rachid Nouicer, Michael Reuter
UNIVERSITY OF MARYLAND
Edmundo Garcia-Solis, Peter Stanskas, Alice Mignerey
Physics Goals of PHOBOS:
Study QCD Vacuum and Confinement
Look for Excess Entropy
• Multiplicity Distribution and Fluctuations
• Source Size and Lifetime
Look for Collective Phenomena over large V
• Low Transverse Momentum
Look for Unusual Medium Effects
• Phi Mass and Width
The Phobos detector
Time-of-Flight Walls
• multiplicity array:
|h| <5.4, Dh=0.1, Dh=p/16
• spectrometer:
0.5<h<1.5, Df=11deg
• vertex detector
• tof
• trigger detectors
• magnet
Spectrometer
Octagon and Vertex
Detector
Magnet
Ring Detectors
first year :
• full multiplicity and vertex detector
• 1 spectrometer arm
• 2 TOF elements
Triggering and data rates
Simple, unbiased trigger:
paddle scintillators 3.7  |h | 4.5
ring cerenkov
4.9  |h|  5.3
Rates at nominal Luminosity L = 1026 cm2 s1
R(Au+Au)
= 600 Hz (b  15 fm)
R(Au+Au, central) = 60 Hz
R(BeamGas)
= 100 Hz
Reduced by vertex timing
R(e+e+)
= 10 Hz
cut
data collection volume
18 kb/ event
=> 60 Tb raw - 430 Tb total / year
Multiplicity array and Vertex detector
Multiplicity measurement:
octagon and 6 ring counters
acceptance: |h| < 5.4 0  f  2p
bin width
Dh = 0.05 - 0.1, Df = p/16
5.0m
2.3m
vertex
octagon
1.1m
ring
counter
interaction
point
-1.1m
-5.0m
-2.3m
Vertex reconstruction
11 cm
5.5 cm
beam
beam
Vertex Resolution:
s = 60 mm
z
Vertex acceptance:
-20cm  z  20 cm
Vertex Reconstruction in x,y:
with tracks reconstructed in
spectrometer
z
z
Multiplicity array
Part of octagon
1 ring counter
Silicon Detector modules used in the
Multiplicity array
Ring module
6.5 cm
8.5cm
Octagon module
120 pads / sensor
Dh~0.05 - 0.1
Df=p/16
64 pads / sensor
Dh~0.05
Df=p/32
Multiplicity Reconstruction
from Energy Loss
Reconstructed multiplicity in Pad i:
Mi = Edepi / (Eisingle • Nitot/Niprim)
Edepi : deposited Energy (angle corrected)
Eisingle: mean energy loss for one particle
traversing pad
Nitot/Niprim : ratio of total/primary tracks
Error on total Multiplicity: 2/3
1.5 * 107 distributions in 1 month at 1% nominal luminosity
M
Event by Event Multiplicity
Average over 50 Events
Spectrometer and Tracking
+
The Magnet
conventional magnet
maximal B-field: 2.1 Tesla
Silicon Detectors mounted
on Spectrometer Frame
Response of Silicon Detector to
285MeV/c Pions - Data!
without gaussian addition
in collaboration with hephy in Vienna
Spectrometer Acceptance
Momentum Resolution
Track Finding - very low P
7 Planes, E>800 keV
8
f (deg.)
Stopping
Kaon
0
-8
20
40
q (deg.)
80
7 Planes, all Hits
8
f (deg.)
60
0
-8
20
40
60
q (deg.)
80
HBT Acceptance for p
Truth
Resolution smeared
Source Parameterization:
C2 = 1 + l * exp(-Qi2 Ri2)
i = L, TO,TS
HBT Capabilities
• “Standard” Scenario • Exotic Scenario I
– Extrapolate from
AGS/Cern Energies
– Very Large Source
• Error on Width: 1.0 MeV
f results after 1 nominal week, 15% central cut, Si pid:
• 50000 f
• Resolution: s(Minv) = 1.6 MeV
– Dominated by momentum resolution
Summary - PHOBOS Highlights
• Coverage for Charged Multiplicity in almost 4 p
with the Multiplicity Array
• Momentum Measurement and Particle Identification
at Mid-rapidity with Low pt Threshold with the
Spectrometer
• Unbiased Taking Data Due to High Data Rate Capability
READY
FOR RHIC START-UP
IN NOVEMBER