charged particle flow measurement for | h |
DESCRIPTION
Charged Particle FLOW measurement for | h |TRANSCRIPT
Charged Particle FLOW measurement for ||<5.3 with
the PHOBOS detector
Inkyu Park (Univ. of Rochester)for the PHOBOS Collaboration
2000-01-17 Flow@PHOBOS - Inkyu Park 2
ARGONNE NATIONAL LABORATORY Birger Back, Nigel George, Alan Wuosmaa
BROOKHAVEN NATIONAL LABORATORYMark Baker, Donald Barton, Alan Carroll, Stephen Gushue, George Heintzelman, Robert Pak,
Louis Remsberg, Peter Steinberg, Andrei SukhanovINSTITUTE OF NUCLEAR PHYSICS, KRAKOW
Andrzej Budzanowski, Roman Holynski, Jerzy Michalowski, Andrzej Olszewski, Pawel Sawicki, Marek Stodulski, Adam Trzupek, Barbara Wosiek, Krzysztof Wozniak
MASSACHUSETTS INSTITUTE OF TECHNOLOGYWit Busza*, Patrick Decowski, Kristjan Gulbrandsen, Conor Henderson, Jay Kane, Judith Katzy,
Piotr Kulinich, Johannes Muelmenstaedt, Heinz Pernegger, Corey Reed, Christof Roland, Gunther Roland,
Leslie Rosenberg, Pradeep Sarin, Stephen Steadman, George Stephans, Gerrit van Nieuwenhuizen,
Carla Vale, Robin Verdier, Bernard Wadsworth, Bolek WyslouchNATIONAL CENTRAL UNIVERSITY, TAIWAN
Willis Lin, Jawluen TangUNIVERSITY OF ROCHESTER
Joshua Hamblen, Erik Johnson, Nazim Khan, Steven Manly, Inkyu Park, Wojtek Skulski, Ray Teng, Frank Wolfs
UNIVERSITY OF ILLINOIS AT CHICAGORussell Betts, Clive Halliwell, David Hofman, Burt Holzman, Wojtek Kucewicz, Don McLeod,
Rachid Nouicer, Michael ReuterUNIVERSITY OF MARYLAND
Richard Bindel, Edmundo Garcia-Solis, Alice Mignerey
*spokesperson
PHOBOS Collaboration
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Physics Goal of RHIC & Flow
Flow
affect other physics: HBT, Spectra, etc
dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R) + ... )
In-plane OR Out-of-plane
Elliptic flow Directed flow
Flow strength
Equation of state
Initial state anisotropy
b (reaction plane)
Degree of thermalization
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PHOBOS Detector setup 2000
Ring Counters
Paddle Trigger Counter
Spectrometer
TOF
Octagon+Vertex
See Robert Pak’s talk
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Au Aux
z
PPPN
ZDC P
ZDC N
Negative
Paddles
Positive Paddles
Paddle counters : Trigger & Centrality
Paddle Signal
Np
art
Paddle Signal
Data MC
See Judith Katzy’s talk
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Spectrometer : Vertex Reconstruction
form 3D vertex z
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octagon
Ring counter
-1.1m
1.1m2.3m
-2.3m
5.0m
-5.0m
• || < 5.3 (, 0 (
Interaction Point
Octagon and Ring detectors
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Hit Definition
Particle direction
Charged particle
deposit energy in pad
hit
event vertex 1 hit = pad with energy > 60
keV
Octagon Ring
Energy deposit (keV) Energy deposit (keV)
60keV 60keV
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Event Selectionvertex available Rings PRings N
• To cover pseudo-rapidity -2.0 to 2.0, only events with vertex -38cm to -30 cm are used
• Rings will cover 3.0 < || < 5.3
• 13K events are used finally for the analysis
-56cm -14cmOctagon
z
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Centrality Bins
Acceptance affected by various strict vertex cuts
Normalized Paddle Signal
Triggered
Accepted
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Event Plane Reconstruction
n = tan-1 ( Xn / Yn ) / n
(Xn,Yn)=w cos(n), w sin(n) )
n
Xn
Yn
(p
ixel
num
ber)
Z (pixel number)
w is weight to compensate for detector
related azimuthal asymmetries
(inverse of hit density)
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Particle distribution w.r.t. Event Plane
N V 2
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• If we know the reaction plane perfectly: Vn = < cos (n(R)) >
Flow Analysis* (Subevent correlation)
• In real experiment, R is unknown: use n
Vnobs = < cos (n(n)) >
<cos(nna,bRcos(n(n
a nb))> )1/2
• Finally, correct for event plane resolution
Vn= Vnobs / < cos (n(n R)) >
-2.0 < < -0.1
RingPRingNSubE (a) SubE (b)
na n
b
* Phys. Rev. C 58, 1671
A. M. Poskanzer,
S. A. Voloshin
0.1 < < 2.0
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Subevent Plane Correlation
Normalized Paddle Signal
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With our hit counting method, high occupancy reduces flow
signal
Occupancy Correction
V2corr = V2
raw / (1 -Occ)
V2raw = < cos (2(hit2)) >
Centrality bin
V2 = V2corr / cos (2(
a b)) > )1/2
Occupancy = fraction of hit
pads
Independent of the magnitude of flow
MC
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Centrality Dependence
midrapidity : || < 1.0
Centrality bin
V2PHOBOS Preliminary
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Centrality Dependence
Hydrodynamic model
V2
Normalized Paddle Signal Errors are statistical only
(systematic errors ~ 0.007)
midrapidity : || < 1.0
SPS
AGS
(STAR : Normalized Nch )
Preliminary
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Pseudorapidity dependence of V2
V2 Averaged over centrality
PHOBOS Preliminary
Errors are statistical only (systematic errors ~ 0.007)
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Pseudorapidity dependence of V2
V2 PHOBOS Preliminary STAR (PRL)
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0 1 2 3 4 5 6
SPS NA49 (QM99)
rapidity
PHOBOS Errors are statistical only (systematic errors ~ 0.007)
STAR : averaged over their centrality
Pion (b<11fm)
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• Elliptic Flow at midrapidity reaches 6-7% in
peripheral collisions, and drops in central
collisions
• Elliptic Flow is a strong function of
pseudorapidity
• Indication of sensitivity to V1 (we are
studying…)
Thank you!
Summary