Systematic Study of High-p T Direct Photon Production with the PHENIX Experiment at RHIC
April 28, 2005Ohio State University, S. Manly1 The Information of Flow at RHIC Not a systematic...
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Transcript of April 28, 2005Ohio State University, S. Manly1 The Information of Flow at RHIC Not a systematic...
April 28, 2005Ohio State University, S. Manly 1
The Information of The Information of Flow at RHICFlow at RHIC
Not a systematic review of historical/RHIC/PHOBOS results. More a personal tour of what I find
interesting with emphasis on PHOBOS results.
Steven ManlyUniv. of Rochester
Ohio State UniversityApril 28, 2005
[email protected]://hertz.pas.rochester.edu/smanly/
April 28, 2005Ohio State University, S. Manly 2
Trying to understand the Trying to understand the different faces of QCD different faces of QCD
Why do we believe in this QCD crap anyway?
April 28, 2005Ohio State University, S. Manly 3
q qqq
Quantum Chromodynamics - QCDQuantum Chromodynamics - QCD
Similar to QED … Similar to QED … But ... Gauge field But ... Gauge field carries the chargecarries the charge
q q
distance
energy density, temperature
rel
ativ
e st
ren
gth
asymptotic freedom
qq qq
confinement
April 28, 2005Ohio State University, S. Manly 4
A few reasons we believe QCD is a good description of the strong interaction?
Deep inelastic scattering: There are quarks.
From D.H. Perkins, Intro. to High Energy Physics
nucleon
parton
P
Px
April 28, 2005Ohio State University, S. Manly 5
A few reasons we believe QCD is a good description of the strong interaction?
No direct observation of quarks: confinement
April 28, 2005Ohio State University, S. Manly 6
A few reasons we believe QCD is a good description of the strong interaction?
ee
qqhadronseeR
)(
P. Burrows, SLAC-PUB7434, 1997
R. Marshall, Z. Phys. C43 (1989) 595
Need the “color” degree of freedom
April 28, 2005Ohio State University, S. Manly 7
A few reasons we believe QCD is a good description of the strong interaction?
Event shapes
e+e- Zo qq e+e- Zo qqg
April 28, 2005Ohio State University, S. Manly 8
A few reasons we believe QCD is a good description of the strong interaction?
Measure the coupling
P. Burrows, SLAC-PUB7434, 1997
April 28, 2005Ohio State University, S. Manly 10qqqq
qqqq
qqq
qqq
qqq
qqq
The essence of mass at the quantum levelThe essence of mass at the quantum level(quantum field theory)(quantum field theory)
Strongly interacting particles interact with the vacuum
condensate … which makes them much heavier than the constituent
quark masses.
April 28, 2005Ohio State University, S. Manly 15
“Flow” = patterns in the energy, momentum, or particle density distributions that we use to ferret out clues as to the nature of the collision/matter
To what extent is the initial geometric
asymmetry mapped into the final state?
View along beamline
April 28, 2005Ohio State University, S. Manly 16
Flow as an experimental probeFlow as an experimental probe
Sensitive to interaction strength
Sensitive to very early times and particle velocities since asymmetry disappears with
time With sufficient coverage, it probes longitudinal
uniformity of system
View along beamline
April 28, 2005Ohio State University, S. Manly 17
(reaction plane)
Flow quantifiedFlow quantified
dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R) + ... )
View along beamline
Fourier decomposition of the azimuthal multiplicity distribution
Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671
Best estimate event plane
iii
iii
w
w
2cos
2sintan
2
1 12
April 28, 2005Ohio State University, S. Manly 18
(reaction plane)
dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R) + ... )
Directed flow
Flow quantifiedFlow quantifiedView from
above
View along beamline
April 28, 2005Ohio State University, S. Manly 19
(reaction plane)
dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R) + ... )
Elliptic flow
Flow quantifiedFlow quantified
View along beamline
April 28, 2005Ohio State University, S. Manly 20
(reaction plane)
dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R) + ... )
Higher terms
Flow quantifiedFlow quantified
View along beamline
April 28, 2005Ohio State University, S. Manly 21
b (reaction plane)
View along beamline
n=2, elliptic flown=2, elliptic flow
April 28, 2005Ohio State University, S. Manly 22
Flow at RHIC to date (a few highlights)Flow at RHIC to date (a few highlights)
Elliptic flow is large near =0 (relative to hydro limit)
||<1
(PHOBOS : Normalized Paddle Signal)
Hydrodynamic limit
STAR: PRL86 (2001) 402
PHOBOS preliminary
Hydrodynamic limit
STAR: PRL86 (2001) 402
PHOBOS preliminary
Thanks to M. Kaneta
April 28, 2005Ohio State University, S. Manly 23
Flow at RHIC to date (a few highlights)Flow at RHIC to date (a few highlights)
Elliptic flow is large near =0 (relative to hydro limit)
V2(pT) grows with pT at low pT, consistent with hydro (including fine structure!)
PRL 91 (2003) 182301
April 28, 2005Ohio State University, S. Manly 24
Flow at RHIC to date (a few highlights)Flow at RHIC to date (a few highlights)
Elliptic flow is large near =0 (relative to hydro limit)
V2(pT) grows with pT at low pT, consistent with hydro
V2(pT) saturates at high pT
STAR 130 GeV 4-cumulant
STAR 130 GeV 2-cumulant
STAR 130 GeV Reaction Plane
5-53% central
Preliminary
PHOBOS 200 GeV0-55% central
pT (GeV/c)
v 2
Preliminary
April 28, 2005Ohio State University, S. Manly 25
Flow at RHIC to date (a few highlights)Flow at RHIC to date (a few highlights)
Elliptic flow is large near =0 (relative to hydro limit)
Partonic energy loss plus quark coalescence may explain saturation and meson-baryon difference
Perhaps viscous corrections to elliptic flow grow with pT reducing v2 Teaney Phys. Rev. C 68 (2004) 034913
V2(pT) grows with pT at low pT, consistent with hydro
V2(pT) saturates at high pT
Xhangbu Xu, Quark Matter 2004nucl-ex/0306007
April 28, 2005Ohio State University, S. Manly 26
Flow at RHIC to date (a few highlights)Flow at RHIC to date (a few highlights)
Elliptic flow is large near =0 (relative to hydro limit)
V2(pT) grows with pT at low pT, consistent with hydro
V2(pT) saturates at high pT
Partonic energy loss plus quark coalescence may explain saturation and meson-baryon difference
Elliptic flow falls off sharply as a function of ||
T.Hirano, K.Tsuda, PRC66,054905(2002).
April 28, 2005Ohio State University, S. Manly 27
Flow at RHIC to date (a few highlights)Flow at RHIC to date (a few highlights)
Elliptic flow is large near =0 (relative to hydro limit)
V2(pT) grows with pT at low pT, consistent with hydro
V2(pT) saturates at high pT
Partonic energy loss plus quark coalescence may explain saturation and meson-baryon difference
Elliptic flow falls off sharply as a function of ||
n2 terms observed
April 28, 2005Ohio State University, S. Manly 28
Flow at RHIC to date (a few highlights)Flow at RHIC to date (a few highlights)
Elliptic flow is large near =0 (relative to hydro limit)
V2(pT) grows with pT at low pT, consistent with hydro
V2(pT) saturates at high pT
Partonic energy loss plus quark coalescence may explain saturation and meson-baryon difference
Elliptic flow falls off sharply as a function of ||
n2 terms observed
Strongly interacting
dense matter! Partonic?
Longitudinal structure of the collision not trivially understood
Systematic study of v2(E,) probes the longitudinal dynamics of the collisionRecent work
April 28, 2005Ohio State University, S. Manly 30
Large coverage
Data at 19.6, 62.4, 130 and 200 GeV
1m2m
5m
0 1 2 3 4 512345
coverage for vtx at z=0
April 28, 2005Ohio State University, S. Manly 31
Subevent technique: correlate event plane in one part of detector to asymmetry in track pattern in other part of detector
Correct for imperfect reaction plane resolution
-2.0 < < -0.1
SubE (a) SubE (b)
na n
b
0.1 < < 2.0
dependence of the multiplicity
Flow: basic methodFlow: basic method
April 28, 2005Ohio State University, S. Manly 32
Pixelized detectorPixelized detector
Hit saturation, grows with occupancy
Sensitivity to flow reduced
Can correct using analog energy deposition
–or-
measure of occupied and unoccupied pads in local region assuming Poisson statistics
April 28, 2005Ohio State University, S. Manly 33
z
Dilutes the flow signal
Remove Background
Estimate from MC and correct
flow signal
Azimuthally symmetric background
+
Azimuthally symmetric backgroundsAzimuthally symmetric backgrounds
April 28, 2005Ohio State University, S. Manly 34
Background suppressionBackground suppression
Works well in Octagon
dE
(keV)cosh
Background!
Technique does not work in rings because angle of incidence is ~90
Beampipe
Detector
Demand energy deposition be consistent with angle
April 28, 2005Ohio State University, S. Manly 36
RingsN Octagon RingsP
Hit-based methodHit-based method
Vertex range -10<z<10
Subevents for reaction plane evaluation
April 28, 2005Ohio State University, S. Manly 37
Flow: method continuedFlow: method continued
Method from Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671
Determine event plane in each subevent, 2±
RingsN Octagon RingsP
April 28, 2005Ohio State University, S. Manly 38
Flow: method continuedFlow: method continued
RingsN Octagon RingsP
Method from Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671
Correlate 2± with hits outside of given subevent to get raw v2
April 28, 2005Ohio State University, S. Manly 39
Flow: method continuedFlow: method continued
Method from Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671
Determine event plane resolution by correlating 2+ and 2
-
RingsN Octagon RingsP
April 28, 2005Ohio State University, S. Manly 40
Flow: method continuedFlow: method continued
Method from Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671
Correct raw v2 by resolution (factor of 1.7 to 3 depending on energy and centrality, well understood)
Correction determined from data
RingsN Octagon RingsP
April 28, 2005Ohio State University, S. Manly 41
Flow: method continuedFlow: method continued
Resolution-corrected v2 is further corrected by ~30%
dilution due to azimuthally symmetric background
effects due to residual bias in 2± due to hole filling
Correction derived from Monte Carlo
RingsN Octagon RingsP
April 28, 2005Ohio State University, S. Manly 42
Flow: method continuedFlow: method continued
Have agreement between:
Two hit-based analyses one “holy”, one not
Track-based analysis with NO background
RingsN Octagon RingsP
April 28, 2005Ohio State University, S. Manly 43
vv2 2 vs. vs. (four energies) (four energies)
(0-40% central Au+Au data)
Bars are 1 “statistical” errors, expect some correlation
April 28, 2005Ohio State University, S. Manly 44
vv2 2 vs. vs. (four energies) (four energies)
(0-40% central Au+Au data)
Boxes are 90% C.L. systematic errors
April 28, 2005Ohio State University, S. Manly 45
vv2 2 vs. vs. (four energies) (four energies)
(0-40% central Au+Au data)
Shape is triangular at all four energies, no evidence of plateau
April 28, 2005Ohio State University, S. Manly 46
vv2 2 vs. vs. (four energies) (four energies)
(0-40% central Au+Au data)
Drop highest || points at 19.6 GeV in following results
April 28, 2005Ohio State University, S. Manly 47
Systematic errorsSystematic errors
Hit definition
Beam orbit/alignment
Subevent definition
Transverse vertex position cut
Bins for weighting matrix definition
Dead channel correction algorithm
Poisson occupancy correction algorithm
Hole filling algorithm
Knowledge of azimuthally symmetric background
dN/d shape
Symmetry in
April 28, 2005Ohio State University, S. Manly 48
vv2 2 vs. vs. (four energy overlay) (four energy overlay)
Only statistical errors shown
Preliminary
Au+Au data(0-40% central)
April 28, 2005Ohio State University, S. Manly 49
ppTT selection important selection important
PHENIX, nucl-ex/0411040
April 28, 2005Ohio State University, S. Manly 50
CGC+Hydro
Flat+Gaussian initialization
T. Hirano, RBRC flow workshop, Nov. 2003
T. Hirano, nucl-th/0410017, presented at ISOMD in July 2004
April 28, 2005Ohio State University, S. Manly 52
M. Csanad, T. Csorgo, B. Lorstad, Nucl.Phys.A742:80-94,2004. [NUCL-TH 0310040]
Buda-Lund hydrodynamic modelBuda-Lund hydrodynamic model
April 28, 2005Ohio State University, S. Manly 53
M. Csanad, T. Csorgo, B. Lorstad, Nucl.Phys.A742:80-94,2004.[NUCL-TH 0310040] and M. Csanad et al, private communication and work in preparation.
April 28, 2005Ohio State University, S. Manly 54
Evolution of vEvolution of v22 with energy with energy
Preliminary
Au+Au data(0-40% central)
Note: pT-integrated values
April 28, 2005Ohio State University, S. Manly 55
Take out differing beam boosts by going into
approximate frame of reference of target
Look at ’ scaling
Extended longitudinal scalingExtended longitudinal scaling
PHOBOS Au+Au results
PRL 91, 052303 (2003)“limiting fragmentation” energy
independence in ’=||-ybeam
April 28, 2005Ohio State University, S. Manly 56
y vs. y vs.
Boost invariant spectra transform as:
)(cosh
cosh
)()(),(
222 TTTT
T
TTT
TTT
TTT
pdydpp
dN
pm
p
pdydpp
dNp
dydpp
dN
d
dyp
ddpp
dN
Jacobian suppresses spectra at low , low pT, and for large mass
April 28, 2005Ohio State University, S. Manly 57
y vs. y vs. : effect on multiplicity: effect on multiplicity
dN/ddN/dy
0
April 28, 2005Ohio State University, S. Manly 58
y vs. y vs. : effect on multiplicity: effect on multiplicity
April 28, 2005Ohio State University, S. Manly 59
y vs. y vs. : effect on v: effect on v22
0
V2()V2(y)
No change in the qualitative features of the result (<20% at =0)
April 28, 2005Ohio State University, S. Manly 61
Only statistical errors shown
Preliminary
Au+Au data
(0-40% central)
Extended longitudinal scaling of vExtended longitudinal scaling of v22
April 28, 2005Ohio State University, S. Manly 62
Longitundinal scaling and elliptic flowLongitundinal scaling and elliptic flow
Only statistical errors shown
Preliminary
Au+Au data(0-40% central)
’=||-ybeam
April 28, 2005Ohio State University, S. Manly 63
Near future: Near future: finalizing directed flowfinalizing directed flow
Cu-Cu flowCu-Cu flow
Does flow scale with multiplicity and eccentricity? Would be strange given success of hydrodynamics.
Different system with different energy density in the initial state, perhaps we test if falling v2 is due to the highly
viscous late hadronic stage
Heinz, nucl-th/0412094 and Teaney, Lauret, Shuryak, nucl-th/0110037
With all the differential flow data and progress in hydro models, we may be entering a stage where we can probe the
nature of the beast.
April 28, 2005Ohio State University, S. Manly 64
ConclusionsConclusions
Interaction length is short - early thermalization likelyInteraction length is short - early thermalization likely
Hydro works well at mid-Hydro works well at mid- … dense, almost ideal fluid … dense, almost ideal fluid
Flow gives evidence for partonic energy loss in medium and Flow gives evidence for partonic energy loss in medium and quark coalescencequark coalescence
Is Hydro/Bjorken/Feynman consistent with multiplicity and Is Hydro/Bjorken/Feynman consistent with multiplicity and elliptic flow data as function of elliptic flow data as function of ηη? Evidence for Landau?? Evidence for Landau?
No indication of sharp change in dynamics of particle No indication of sharp change in dynamics of particle production as function of production as function of or E from 20-200 GeV. But maybe or E from 20-200 GeV. But maybe a smooth evolution as initial energy density decreased and a smooth evolution as initial energy density decreased and viscosity/time spent as hadronic gas increases?viscosity/time spent as hadronic gas increases?
Stay tuned for Cu-Cu results.Stay tuned for Cu-Cu results.
April 28, 2005Ohio State University, S. Manly 68
Acceptance (phase space) weightingAcceptance (phase space) weighting
Octagonal detector
Require circular symmetry for equal phase space per pixel
Pixel’s azimuthal phase space coverage depends on location
Relative phase space weight in annular rings = <Nocc>-1
April 28, 2005Ohio State University, S. Manly 69
Determining the collision pointDetermining the collision point
High Resolution
extrapolate spectrometer tracks
Low Resolution
octagon hit density peaks at vertex z
position
April 28, 2005Ohio State University, S. Manly 70
RingsN Octagon RingsP
Spec holes
Vtx holes
Detector symmetry issues where SPEC vertex efficiency highest
Most data taken with trigger in place to enhance tracking efficiency
April 28, 2005Ohio State University, S. Manly 71
RingsN Octagon RingsP
Offset vtx methodOffset vtx method
Limited vertex range along z
Subevents for reaction plane evaluation
Good azimuthal symmetry
Fewer events, no 19.6 GeV data
Technique used for published elliptic flow signal at 130 GeV
April 28, 2005Ohio State University, S. Manly 72
Dealing with the holesDealing with the holes
RingsN Octagon RingsP
Inner layer of vertex detector fills holes in top and bottom. Must map hits from Si with different pad pattern and radius onto a “virtual” octagon Si layer
April 28, 2005Ohio State University, S. Manly 73
Dealing with the holesDealing with the holes
RingsN Octagon RingsP
Fill spectrometer holes by extrapolating hit density from adjoining detectors onto a virtual Si layer. (Actual spec layer 1 is much smaller than the hole in the octagon.)
April 28, 2005Ohio State University, S. Manly 74
RingsN Octagon RingsP
Track-based methodTrack-based method
Vertex range -8<z<10
Subevents for reaction plane
Momentum analysis
200 GeV data
Gap between tracks and subevents large
Little/no background
April 28, 2005Ohio State University, S. Manly 75
Elliptic flow vs Elliptic flow vs
width of bin
PHOBOSPreliminary
central 3-15%midcentral 15-25%peripheral 25-50%
Hit-based method
h±
M. Belt-Tonjes, Quark Matter 2004
200 GeV Au+Au
April 28, 2005Ohio State University, S. Manly 76
Track-basedHit-based
peripheral25-50%h±
v 2
PHOBOS Preliminary
Track-basedHit-based
midcentral15-25%h±
v 2
PHOBOS Preliminary
central3-15%h±
Track-basedHit-based
v 2
PHOBOS Preliminary
v2 vs. v2 vs. 200 GeV method comparison 200 GeV method comparison
April 28, 2005Ohio State University, S. Manly 77
STAR 130 GeV 4-cumulant
STAR 130 GeV 2-cumulant
STAR 130 GeV Reaction Plane5-53% central
Preliminary
PHOBOS 200 GeV0-55% central
pt (GeV/c)
v 2
Elliptic flow vs pElliptic flow vs pTT
Preliminary
April 28, 2005Ohio State University, S. Manly 78
Transformation of spectra from to y leads to
suppression of multiplicity at low pt and low ||
This leads to an enhancement of inclusive v2
at mid-
P. Kolb, Proc. of 17th Winter Workshop on Nuclear Dynamics (2001)
T. Hirano, BNL-Riken Workshop on Collective Flow and the QGP (Nov. 2003)
~10%
April 28, 2005Ohio State University, S. Manly 79
Poisson occupancy weighting
)1ln(
1),(
unocc
occ
N
N
eOcc
April 28, 2005Ohio State University, S. Manly 80
Directed flow as function of ’
Limiting fragmentationLimiting fragmentation
PHOBOS Au+Au results
M. Belt-Tonjes, QM04
April 28, 2005Ohio State University, S. Manly 81
Molnar and Voloshin, nucl-th/0302014
Partonic energy loss alone leads drop at very large pT and does not account for meson/baryon differences
Quark coalescence vs. fragmentationQuark coalescence vs. fragmentation
nucl-ex/0306007nucl-ex/0305013
April 28, 2005Ohio State University, S. Manly 82
v 1
PHOBOS Preliminary
PHOBOS AuAu √sNN=19.6 GeV
NA49 PbPb √sNN=17.2 GeV
Phys.Rev.C68, 034903, 2003
6-55%
MinimumBias
h±
±
19.6 GeV AuAu & 17.2 GeV PbPb
April 28, 2005Ohio State University, S. Manly 83
STAR AuAu 200 GeV 10-70% central
v1 at 200 GeV AuAu:PHOBOS & STARv 1
STAR, PRL 92 (2004) 062301
PHOBOS Preliminary
PHOBOS 6-55% centralh±