cone is medium response, ridge is medium itself
DESCRIPTION
Cone is medium response, Ridge is medium itself. Fuqiang Wang Purdue University For the STAR Collaboration. Bridger ridge, Montana. Plan of talk. Away-side cone: medium response to hard probes. Near-side ridge: medium response or itself ?. High p T trigger particle. Df. trigger jet. - PowerPoint PPT PresentationTRANSCRIPT
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Cone is medium response, Ridge is medium itself.
Fuqiang WangPurdue University
For the STAR Collaboration
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Plan of talk
• Away-side cone: medium response to hard probes
• Near-side ridge: medium response or itself?
Bridger ridge, Montana
2Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
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The away-side structure
3
p+p
Au+Au
Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
PHENIX
Df
High pTtrigger particle
associatedparticles Away-
side
triggerjet
0 p1-1 Df
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Possible physics scenariospT
trig=3-4 GeV/c, pTassoc=1-2.5 GeV/c
Away-side
triggerjet
0 p1-1 Df
trigger jet
Mach coneaway
away
trigger jet
deflected jets away
event1
event2
Surface bias
4Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
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Df1= f1-ftrig
Df2
p
p0
0
= f2-ftrig
3-particle azimuthal correlation
Df1
Df2
p0
0
p
away
trigger jet
deflected jets away
event1
event2
trigger jet
Mach cone
away away
signature of conicalemission
5Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
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Evidence of conical emission
d+Au Au+Au central
Df1
Df2
p00
p
Away-side
STAR, PRL 102, 052302 (2009)
trigger
6Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
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Conical emission angle
q = 1.37 ± 0.02 (stat.) ± 0.06 (syst.)
STAR, PRL 102, 052302 (2009)
Away-side
trigger
q
Constant cone angle vs pT suggests Mach Cone shock waves may be the underlying mechanism.
7Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
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Higher trigger pT
4 < pTtrig < 6 GeV/c
1 < pTassoc < 2.5 GeV/c
6 < pTtrig < 10 GeV/c
1 < pTassoc < 2.5 GeV/c
1 < pTassoc < 2 GeV/c
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Theory calculations
Parton energy loss:Renk et al. PRC 76, 014908 (2007)
pQCD + hydro:Neufeld et al.arXiv:0807.2996 quark v = 0.99955
(z -
ut)
x (rx)mD
2 T
x gz (rx)
mD2 T
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AdS/CFT Correspondence
N = 4 Super-Yang-Millstheory in 4d with SU(NC)
Maldacena (1997), Gubser, Klebanov,Polyakov; Witten (1998)
YM observables at infinite NC and infinite coupling can be computed using classical gravity.
A string theory in 5d AdS
Measure heavy quark Mach-cone shock waves: Experimental consequence of string theory?
Chesler & Yaffe
arXiv:0712.0050
Heavy quark u = 0.75c
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qM = 1.37
p
HGcS = 0.45
QGPcS = √1/3 = 0.58
Mixed phasecS = 0
Speed of sound?
cS far smaller than HG or QGP. Must have mixed phase (phase transition).
2 /Sc p EOS: p()
speed of soundcS ~ 0.2
However, model calculations indicate that Mach Cone angle can be altered by medium flow.
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Investigating flow effect on cone angle
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Fit to large Dh azimuthal correlations
2 Gaus: Ridge at 0 and ridge at p, same shape, diff. magnitudes2 Gaus: identical conical emission peaks symmetric about p.
STAR Preliminary
13Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
Au+Au 20-60%, 3<pTtrig<4, 1<pT
trig<2 GeV/c
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• Cone angle takes off after trigger fs=45o.
• Split in pT after fs=45o.• Cone angle ~constant
over pT at fs<45o.
STAR Preliminary
STAR Preliminary
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Is there a back-to-back RIDGE?
RP
Trig.
Ridge
Away 2
Away 1
Near Jet
Away-Side Ridge
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Connection between near- and away-side
Away-side
0 p1-1 Df
STAR Preliminary
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∆φ ∆φ ∆φ ∆φ ∆φ ∆φ
• Separate 1st and 2nd quadrants trigger particles• Azimuthal correlation for large |Dh|>0.7• Near-side ridge Gauss repeated at “+π”• Subtract back-to-back symmetric ridge peaks
∆φ ∆φ ∆φ ∆φ ∆φ ∆φ
STAR Preliminary
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Away-side asymmetric cone positions
• Evidence of flow effect on conical emission.• Important to disentangle flow effect and conical emission angle.
1st cone peak
2nd Cone peak
φs
∆φ
STAR Preliminary
RP
trigger2nd Cone
1st cone
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Df
trigger particlepT > 3 GeV/c
assoc. particlepT =1-2 GeV/c
d+Au
Au+Au ridge
Df Dh
The longitudinal ridge
h ~ 1h ~ 0
High-pT
trigger particle
Dh
associated particle
|Df|
<0.7
Bridger ridge, Montana
19Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
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What’s already known about ridge
M. Daugherity (STAR), QM’08, J.Phys.G35:104090,2008
STAR, arXiv:0909.0191
• Ridge present in untriggered correlation.
• Ridge increases with centrality.• Ridge pt spectrum is a bit harder than bulk. • Ridge particle composition similar to bulk.
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Ridge extended to very large DhPHOBOS, arXiv:0903.2811
STAR Preliminary
2.7<|Dh|<3.9pT
assoc > 1.0 GeV/c
STAR, arXiv:nucl-ex/0701061
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New insights from RP-dependent dihadron correlations
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jet
ridge
Dh cut to “separate” jet and ridge
Dh
|∆η|>0.7 = ridge + away-sideJet = (|∆η|<0.7) – Accept.*(|∆η|>0.7)
assuming ridge is uniform in ∆η.Dh
Feng, QM’06. STAR Preliminary
Au+Au 20-60%, 3<pTtrig<4, 1.5<pT
trig<2.0 GeV/c
d+Au
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Ridge decreases with RP
Ridge drops when trigger particle moves away from RP.
in-plane out-of-planetrigger |fs|
STAR Preliminary
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A model prediction motivated by data
in-planejet flow alignedmore ridge
out-o
f-pla
neje
t flow
misa
ligne
dle
ss ri
dge
Chiu,Hwa, arXiv:0809.3018Correlated Emission Model (CEM)
Alignment of jet propagation and medium flow produces the ridge.
If correct, would produce measureable asymmetry in near-side ridge correlation peak.
Correlated Emission Model (CEM)
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Remove away-side from large Dh correlation
RidgeJet
Konzer, QM’09. STAR Preliminary|∆η|>0.7
∆f=fassoc – ftrig
Trig. pt=3-4 GeV/c, assoc pt=1-1.5 GeV/c
φs = 0 to -15 -15 to -30 -30 to -45 -45 to -60 -60 to -75 -75 to -90
-1 0 1 π
0.05
0
Au-Au 20-60%
ZYAM
• Jet remains constant• Ridge Decreases
• Jet symmetric• Ridge asymmetric
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Correlation Asymmetry
0 1 1 0
0 1 1 0
N NA
N Nf f
f f
-
-
-
in-plane
trigger pt=3-4 GeV/c
Jet
Ridge
|fs|= ftrig – ψRP out-of-plane
CEM model
Ridge: assoc pt=1-1.5 GeV/cRidge: assoc pt=1.5-2 GeV/cJet: assoc pt=1.5-2 GeV/c
STAR Preliminary
• Away-side is Asymmetric (not shown in plot).
• Jet is symmetric.
• Ridge is Asymmetric!
• Ridge may be due to jet-flow alignment.
v2 syst.
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New insights from 3-particle Dh-Dh correlation
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How does long Dh come about?
Many models on the market. |Df|<0.73<pT
trig<10 GeV/c, 1<pTassoc<3 GeV/c
d+Au Central Au+Au
Netrakanti, QM’09. arXiv:0907.4744STAR Preliminary
3-particle Dh-Dh correlations
N. Armesto et al., Phys. Rev. Lett. 93 (2004) 242301
Fuqiang Wang Nucleus-Nucleus 2009, August 2009 29
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3<pTtrig<10 GeV/c
1<pTassoc<3 GeV/c
|Df|<0.7
3-particle Dh-Dh correlations
Charge independent (All)
AALike = (AALikeTLike + AALikeTUnlike)
AAUnlike = All - AALike
dAu AuAu 12%
STAR Preliminary
Netrakanti, QM’09. STAR Preliminary
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Separate jet and ridgeJet has charge ordering ridge does not
ridge
Same-sign triplets: Only ridge, no jet.
jet
Netrakanti, QM’09. arXiv:0907.4744.STAR Preliminary
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Ridge is structureless
No prominent subtructures in ridge. (jet) = 0.25 0.09 (ridge) = 1.53 0.41
Radial Projection Angular Projection
STAR Preliminary
Netrakanti, QM’09. arXiv:0907.4744. STAR Preliminary
Rx
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Ridge-jet cross pairs
2
2
Assuming Poisson statistics:
(0.8 / ) 1.26 0.50
(0.3 / ) 2 (0.8 / ) (0.3 / ) 0.16 0.17 0.09 0.53, 0.08
x x x
y y x y zz yy z
-
33
0.190.31
0.130.27
0.060.04
From 3-particle - correlation:
N pairs 1.42
N ridge pairs 1.26
N jet pairs and jet-ridge pairs 0.16
h h-
-
-
D D
From 2-particle correlation:N assoc 1.1N ridge 0.8N jet-like 0.3
hD
Let fraction of events containing ridgefraction of events containing jetfraction of events containing both ridge and jet
xyz
0.050.11
0.150.20
0.050.04
With systematic errors:
0.50
0.53
0.08
x
y
z
-
-
-
Ridge and jet appear to be anti-correlated.
Netrakanti, QM’09. arXiv:0907.4744. STAR Preliminary
Fuqiang Wang
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Experimental facts1) Ridge increases with centrality.2) Ridge spectrum a bit harder than bulk.3) Ridge particle composition similar to bulk.4) Ridge present in untriggered correlation.5) Ridge is mainly in-plane.6) Ridge is asymmetric in Df.7) Ridge is very wide.8) Ridge is random.9) No jet-ridge cross-talk.10) Ridge may be back-to-back.11) Ridge seems unrelated to jet.
Now let’s go to models…
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In-medium rad. + long. Flow push
• Ridge increases with centrality.
• Ridge spectrum a bit harder than bulk.
• Ridge particle composition similar to bulk.
• Ridge present in untriggered correlation.
• Ridge is mainly in-plane.
• Ridge is asymmetric in Df.
• Ridge is very wide.
• Ridge is random.
• No jet-ridge cross-talk.
• Ridge may be back-to-back.
• Ridge seems unrelated to jet.
N. Armesto et al., Phys. Rev. Lett. 93 (2004) 242301
xx
x
x35Fuqiang Wang
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Turbulent color field
• Ridge increases with centrality.
• Ridge spectrum a bit harder than bulk.
• Ridge particle composition similar to bulk.
• Ridge present in untriggered correlation.
• Ridge is mainly in-plane.
• Ridge is asymmetric in Df.
• Ridge is very wide.
• Ridge is random.
• No jet-ridge cross-talk.
• Ridge may be back-to-back.
• Ridge seems unrelated to jet.
A. Majumder et al., Phys. Rev. Lett. 99 (2004) 042301
x
x36Fuqiang Wang
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Recombination of thermal+shower partons
37
• Ridge increases with centrality.
• Ridge spectrum a bit harder than bulk.
• Ridge particle composition similar to bulk.
• Ridge present in untriggered correlation.
• Ridge is mainly in-plane.
• Ridge is asymmetric in Df.
• Ridge is very wide.
• Ridge is random.
• No jet-ridge cross-talk.
• Ridge may be back-to-back.
• Ridge seems unrelated to jet.
R.C. Hwa, C.B. Chiu, Phys. Rev. C 72 (2005) 034903
x
x
x
Fuqiang Wang
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Momentum kick model
38
• Ridge increases with centrality.
• Ridge spectrum a bit harder than bulk.
• Ridge particle composition similar to bulk.
• Ridge present in untriggered correlation.
• Ridge is mainly in-plane.
• Ridge is asymmetric in Df.
• Ridge is very wide.
• Ridge is random.
• No jet-ridge cross-talk.
• Ridge may be back-to-back.
• Ridge seems unrelated to jet.
C.Y. Wong hep-ph:0712.3282
xx
x
x
Fuqiang Wang
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Transverse flow boost
39
• Ridge increases with centrality.
• Ridge spectrum a bit harder than bulk.
• Ridge particle composition similar to bulk.
• Ridge present in untriggered correlation.
• Ridge is mainly in-plane.
• Ridge is asymmetric in Df.
• Ridge is very wide.
• Ridge is random.
• No jet-ridge cross-talk.
• Ridge may be back-to-back.
• Ridge seems unrelated to jet.
S.A. Voloshin, Phys. Lett. B 632 (2006) 490; E. Shuryak, Phys. Rev. C 76 (2007) 047901
xFuqiang Wang
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Glasma flux tube fluctuation + radial flow
40
• Ridge increases with centrality.
• Ridge spectrum a bit harder than bulk.
• Ridge particle composition similar to bulk.
• Ridge present in untriggered correlation.
• Ridge is mainly in-plane.
• Ridge is asymmetric in Df.
• Ridge is very wide.
• Ridge is random.
• No jet-ridge cross-talk.
• Ridge may be back-to-back.
• Ridge seems unrelated to jet.
R. Venugopalan et al., arXiv:0902.4435
ridgeridge
Fluctuation of color flux tubes excess ridge particles
(larger in-plane due to flow?)x
Fuqiang Wang
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Summary and open questions• Conical emission of correlated particles.
Medium response to hard probes. Suggests Mach cone shock waves.– What distortion to Mach angle by medium? – How to extract speed of sound? EOS?
• Ridge is uniform in pseudo-rapidity.Likely medium itself at early time.– Is it due to color flux tubes?– What additional work to falsify this and other
models, or learn something from them?
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Backups
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v2 systematic uncertainties
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On-diag projection
Off-diag projection
On-diag projection
Off-diag projection
Jet-like 3-p correlation RP-frame cumulant Lab-frame cumulant
3 1 2 3 1 2 2 1 2 1 2 1 1 2 2 2 1 1 1 1 1 1 2ˆ ( , , ) ( , , ) ( , ) ( ) ( , ) ( ) ( , ) ( ) 2 ( ) ( ) ( )t t t t t t - - -
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Df
trigger particlepT > 3 GeV/c
assoc. particlepT =1-2 GeV/c
Large combinatorics
N jet particles ~ 1, N bkgd particles ~ 20
pTtrig=3-4 GeV/c, pT
assoc=1-2 GeV/c
Extremely difficult analysis. Careful subtraction of bkgd. Extensive assessment of systematics.
Combinatorial pair bkgd is huge!
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What’s left on the away-side?
first peak
second peak
φs φs φs
Differential pathlength sensitivity
2
3
4
0 p/2
0.1
0.2
Peak position
Peak areaPeak
0.4
0.5
0.6
Peak distance
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• Jet constant with fs.• Ridge decreases with fs.• Cone increases with fs.
• Jet decreases with pT.• Ridge constant with pT.• Cone decreases with pT.
STAR Preliminary
STAR Preliminary
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Black : Raw signal
Pink : Mixed-event background
Blue : Scaled bkgd by ZYA1
Red : Raw signal – bkgd
2-particle correlationAuAu ZDC central (0-12%) triggered data, 3<pT
Trig<10 GeV/c, 1<pTAsso<3 GeV/c
Dh acceptance corrected
STAR Preliminary
|Df|<0.7
|Df|<0.7
Ridge
49Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
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3-particle correlation background
Raw Raw Raw signal Raw Bkg Hard-Soft Bkg1 Bkg1 Bkg1 Bkg2
correlated
Soft-Soft
- -
50Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang
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Jet and Ridge contributions
AAlikeTlike : No JetOnly Ridge
Ridge (T- A+) A+) = Ridge (T+ A+) A+)Ridge (T+ A- ) A-) = Ridge (T- A- ) A-)Ridge (T+ A-) A+) = Ridge (T+ A+) A+)Ridge (T- A+ ) A-) = Ridge (T- A- ) A-)
Netrakanti, QM’09. STAR Preliminary
51Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang