s. manly – u. rochester xi’an, china, nov. 23, 20061 the eccentricities of flow s. manly...
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S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 1
The eccentricities of flow
S. Manly
University of Rochester
International Workshop on Hadron Physics and Properties of High Baryon Density Matter
Xi’An, China
November 23, 2006
Direct evidence for color strings?
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 2
ec·cen·tric·i·ty ( k s n-tr s -t ) n. pl. ec·cen·tric·i·ties
The quality of being eccentric. Deviation from the normal, expected, or established.
An example or instance of eccentric behavior. Physics. The distance between the center of an eccentric and its axis. Mathematics. The ratio of the distance of any point on a conic section
from a focus to its distance from the corresponding directrix. This ratio is constant for any particular conic section.
From American Heritage Dictionary
The eccentricities of flow
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 3
Burak Alver, Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton,
Russell Betts,
Richard Bindel, Wit Busza (Spokesperson), Vasundhara Chetluru, Edmundo
García, Tomasz Gburek, Joshua Hamblen, Conor Henderson, David Hofman,
Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Chia Ming
Kuo, Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey,
Gerrit van Nieuwenhuizen,
Rachid Nouicer, Andrzej Olszewski, Robert Pak, Corey Reed, Christof Roland,
Gunther Roland, Joe Sagerer, Peter Steinberg, George Stephans, Andrei
Sukhanov, Marguerite Belt Tonjes, Adam Trzupek, Sergei Vaurynovich, Robin
Verdier,
Gábor Veres, Peter Walters, Edward Wenger, Frank Wolfs, Barbara Wosiek,
Krzysztof Woźniak, Bolek Wysłouch
ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORYINSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY
NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGOUNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER
The PHOBOS Collaboration
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 4
I offer a humble apology for some repetition to those of you who saw the PHOBOS talks in Shanghai …
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 5
Average Flow in PHOBOS
Ring counter
Octagon
Spectrometer arm
Paddle trigger
Vertex detector
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 6
Correlate reaction plane determined from azimuthal pattern of hits in one part of detector
Subevent A
Average Flow in PHOBOS
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 7
with azimuthal pattern of hits in another part of the detector
Average Flow in PHOBOS
Subevent B
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 8
Or with tracks identified in the spectrometer arms
Average Flow in PHOBOS
Tracks
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 9
Separation of correlated subevents typically large in
Average Flow in PHOBOS
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 10
PHOBOS has made differential measurements of the average flow:
CentralitypT
PseudorapidityEnergySpecies
Flow in PHOBOS
I will give you an update of ongoing work on understanding how flow scales from species to species and a new event-by-event measurement
of fluctuations in v2
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 11
Elliptic Flow: new results for Cu-Cu at 22.4 GeV
Au+AuAu+AuAu+Au:PHOBOS CollaborationPRL. 94 (2005) 122303
Cu+Cu:PHOBOS CollaborationPRL: nucl-ex/0610037 Cu+CuCu+CuPreliminary
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 12
Au+Au:PHOBOS CollaborationPRL 97, 012301 (2006)
Cu+Cu at 200, 62.4 GeV:PHOBOS CollaborationPRL: nucl-ex/0610037
Statistical errors onlyStatistical errors only
Elliptic Flow: new results for Cu-Cu at 22.4 GeV
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 13
Preliminary
Preliminary
Au+Au Au+Au
0-20%0-20% 20-40%20-40%
Cu+CuCu+Cu
• Track-based method 0 < < 1.6
Elliptic Flow: Au+Au and Cu+Cu v2 vs pt comparison
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 14
Statistical errors onlyStandard Eccentricity
PHOBOS CollaborationPRL: nucl-ex/0610037
Au+Au200 GeV
Cu+Cu200 GeV
Statistical errors only
200 GeV
PRL: nucl-ex/0610037
Au+Au 200 GeV
Cu+Cu200 GeV
PRC C72, 051901R (2005)
Scaling out the geometry
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 15
Participant Eccentricity
PHOBOS CollaborationPRL: nucl-ex/0610037
Au+Au 200 GeVCu+Cu
200 GeV
Statistical errors only
PHOBOS CollaborationPRL: nucl-ex/0610037
Cu+Cu200 GeV
Au+Au 200 GeV
Scaling out the geometry
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 16
It has been suggested that v2 may scale as instead of
- Bhalerao, Ollitrault – PLB 641, 260 (2006)- Ollitrault – private communications (2006)
• In Collaboration with Ulrich Heinz
2partε partε
PHOBOS MCThe difference
between
is as small as our estimate of the
robustness of the calculation … will
ignore for now.
What is the appropriate form of the eccentricity scaling?
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 17
STAR, NA49 and E877 data taken from STAR Collaboration, Phys.Rev. C66 (2002) 034904 with no adjustments
Statistical errors only
Au+Au at 200, 130, 62.4 and 19.6 GeV :PHOBOS CollaborationPRL 97, 012301 (2006)
Cu+Cu at 200, 62.4 GeV:PHOBOS CollaborationPRL: nucl-ex/0610037
Cu+Cu at 22.4 GeV PHOBOS Preliminary
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 18
Similar area density (1/S)dN/dy Similar area density (1/S)dN/dy
Statistical errors only
Similar area density (1/S)dN/dy Similar area density (1/S)dN/dy
and and scaled by scaled by partpartStatistical errors only
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 19
Au+Au vs. Cu+Cu at Au+Au vs. Cu+Cu at 200 GeV200 GeV Au+Au vs. Cu+Cu at Au+Au vs. Cu+Cu at 62.4 GeV62.4 GeV
Same area density (1/S)dN/dy Same area density (1/S)dN/dy and and Scaled by Scaled by partpart
Statistical errors onlyStatistical errors only
Npart=80Npart=82
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 20
Scaled by Scaled by partpart
Same centrality (40%)Same centrality (40%)
Scaled by Scaled by partpart
Same area density (1/S)dN/dySame area density (1/S)dN/dy Statistical errors only Statistical errors only
PHOBOS
PHOBOS
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 21
Elliptic flow develops event-by-event with respect to the participant ellipse
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 22
Expected fluctuations from the part model
Elliptic flow develops event-by-event with respect to the participant ellipse
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 23
A new event-by-event flow analysis from PHOBOS
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 24
A new event-by-event flow analysis from PHOBOS
Determine v2obs
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 25
A new event-by-event flow analysis from PHOBOS
Determine v2obs
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 26
A new event-by-event flow analysis from PHOBOS
Construct kernel
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 27
A new event-by-event flow analysis from PHOBOS
Determine dynamical fluctuations
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006
Event-by-event mean v2 vs published results
|η|<1<v2>
PRC 72, 051901 (2005)
Number of participants
Very good agreement of the event-by-event measured mean v2 with the hit- and tracked-based, event averaged, published results
<v2>(|η|<1) = 0.5 x (11/12 <v2triangular> + <v2
trapezodial>)
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006
Elliptic flow fluctuations: <v2> and σv2
Au+Au 200 GeV
⟨v2 ⟩
Number of participants
|η|<1 PHOBOS preliminary (90% C.L.)• <v2>
Au+Au 200 GeV
v 2
Number of participants
PHOBOS preliminary (90% C.L.)• σv2
|η|<1
“Scaling” errors cancel in the ratio:relative fluctuations, σv2/<v2>
Mean elliptic flow Dynamical flow fluctuations
Systematic errors: Variation in η-shape Variation of f(v2) MC response Vertex binning Ф0 binning
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006
Number of participants
PHOBOS preliminary (90% C.L.)• σv2/<v2>
|η|<1 Au+Au 200 GeV
2
v
v2
Elliptic flow fluctuations: σv2/ <v2>
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 31
Elliptic flow fluctuations: σv2/ <v2>
Number of participants
PHOBOS preliminary (90% C.L.)• σv2/<v2>
|η|<1 Au+Au 200 GeV
Number of participants
PHOBOS preliminary (90% C.L.)• σv2/<v2>
|η|<1 Au+Au 200 GeV
2
v
v2
MC with nofluctuations
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 32
Number of participants
PHOBOS preliminary (90% C.L.)• σv2/<v2>
|η|<1 Au+Au 200 GeV
2
v
v2
MC with nofluctuations
Participanteccentricitymodel prediction
part
part
Elliptic flow fluctuations: σv2/ <v2>
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 33
Things to consider and naïve questionsHow seriously should we take this Glauber-
driven participant eccentricity model?
Number of participants
2
v
v2
Allows us to make sense of both the system size scaling and fluctuations in the data
Really need Cu-Cu fluctuations measurement where the eccentricity fluctuations will be larger … let’s hope the measurements can be made
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 34
Things to consider and naïve questionsHow seriously should we take this Glauber-
driven participant eccentricity model?
Number of participants
2
v
v2
PHOBOS fluctuations analysis depends on MC … things not yet in the MC used to determine the kernel (such as short range correlations) can show up as fluctuations
Fortunately, the wonderful and complementary STAR measurement (P. Sorensen – QM2006) provides a consistency check. Data-driven and independent. Agrees well.
Measurement will likely hold up
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 35
Things to consider and naïve questionsHow seriously should we take this Glauber-
driven participant eccentricity model?
Number of participants
2
v
v2
Participant eccentricity model calculation has proven to be robust during studies that followed its introduction at QM2005
It seems we should take it seriously
Should we be bothered that we don’t have much room for other sources of fluctuations?
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 36
Things to consider and naïve questionsIf we take the participant eccentricity model
seriously, what do we learn?
Whatever the form of the matter in the early stage of the collision, it seems the relevant interactions that drive the flow signal are initially localized transversely in a way similar to the participant nucleons.
Inconsistent with any picture where the initial state is driven by a large number of low-x partons that fill the nuclear transverse area.
S. Manly – U. Rochester Xi’an, China, Nov. 23, 2006 37
Things to consider and naïve questions
It seems we are seeing transversely localized parton production with a granularity not so different from the interacting nucleons! Something
like color strings? Is this telling us something about the reality of some models vs. others? This seems rather fundamental … are there
other measurements that show “stringiness” so directly?
If we take the participant eccentricity model seriously, what do we learn?