Soft Contribution to the Hard Ridge George Moschelli Wayne State University 26,WWND, January 2-10,...
-
date post
22-Dec-2015 -
Category
Documents
-
view
216 -
download
2
Transcript of Soft Contribution to the Hard Ridge George Moschelli Wayne State University 26,WWND, January 2-10,...
Soft Contribution to the Hard Ridge
George MoschelliWayne State University26,WWND, January 2-10, 2009
Ocho Rios, Jamaica
The Ridge• Hard Ridge: jet trigger• Soft Ridge: no trigger• Flow and jetsLong Range Correlations• Flux Tubes, Glasma, and CorrelationsComparison to Experiment• Blast Wave Flow + Glasma• pt Dependence• Soft and Hard Ridge from STAR
arXiv:0910.3590 [nucl-th] GM, Sean Gavin
Phys.Rev.C79,051902, arXiv:0806.4718 [nucl-th]Sean Gavin, Larry McLerran, G. M.
Hard Ridge: Jet + Associated Particles
Hard Ridge: Near Side Peak• Peaked near = 0 • Broad in
STAR: arXiv:0909.0191
€
1
N trig
d2N
dΔφ dΔη
Measure
• High pt trigger
• Yield of associated particles per trigger
How does the formation of the ridge at large depend on jets?
Soft Ridge: Untriggered Correlationstwo particle correlations with no jet tag
central
STAR: arXiv:0806.2121
Soft and Hard Ridges Similar• Peaked near = 0 • Wider in than hard ridge• Broad in • Jet peak?
ρ(η ,φ)ρ ref
=pairs − (singles)2
singles
Measure
peripheral
Common Features• width increases with centrality• peripheral ~ proton+proton
Near Side Peak: Flow
Fluid cell
~1 fm/c Freeze out
Azimuthal correlations come from flow.
• Particles are pushed to higher pt and and focused to a smaller azimuthal angle depending on the push.
• The ridge should narrow in
with increasing pt cuts.
• Mean flow depends on position
• Opening angle for each fluid element depends on radial position
Near Side Peak: Jets + Flow
Quenched away jet
Fluid cell
~1 fm/c Freeze out
Jet Correlations With Bulk
• Correlation of flow and jet particles if produced nearby in transverse plane
• Surviving jets tend to be more radial, due to quenching.
• Bulk particles are pushed into the radial direction by flow
Claim:
Soft ridge explained by bulk flow
Hard ridge: additional jet-bulk contribution
E. Shuryak, Phys. Rev. C 76, 047901 (2007)
Flow Works
Takahashi, Tavares, Qian, Grassi, Hama, Kodama, Xu
correlations NEXUS strings
transverse boostSPHERIO hydro
Voloshin; Pruneau, Gavin, Voloshin;Gavin, Moschelli, McLerran; Shuryak;Mocsy & Sorenson
Blast Wave Model
Hydrodynamics
CGC Flux TubesDusling, Gelis, Lappi, & Venugopalan arXiv:0911.2720
Correlations• Partons from the same tube are correlated
• Rapidity reach: Causally disconnected
Flux Tubes and Glasma
Flux Tubes: longitudinal fields early on
• Tubesquarks+gluonsSingle flux tube phase space density of gluons
• Flux tube transverse size
• Number of flux tubes
• Gluon rapidity densityKharzeev & Nardi
Flux Tubes and Correlations
• Long range Glasma fluctuations scale the phase space density
Dumitru, Gelis, McLerran & Venugopalan;Gavin, McLerran & GM
• Correlation Strength
• Energy and centrality dependence
flux tube transverse size ~ Qs
-1 << RA
Correlation function
Soft Ridge
• Qs dependence: 200 GeV Au+Au 62 GeV, Cu+Cu
Glasma Dependence
Blast Wave
• Boltzmann Dist. f (p,x)
• Scale factor to fit 200 GeV only
• Centrality dependence on blast wave parameters (v and T) 10% uncertainty
• Blast wave only (dashed) fails
Comparison and LHC
LHC
Au+Au 200 GeV
Au+Au 62 GeV
Cu+Cu 62 GeV
Cu+Cu 200 GeV
Caution: Blast Wave parameters for LHC taken from Au+Au 200 GeV
Soft Ridge: Angular Correlations
0
0.2
0.4
0.6
0 0.5 1 1.5 2
Peak Width
Fit using Gaussian + offset
• Range:
• Error band: 20% shift in fit range
• Uncertainty due to experimental definition of peak
• A width is approximately independent of energy
• The width should decrease with increasing pt range
Most Central Width vs. pt
Soft Ridge vs. pt
• Jet-Bulk and Jet-Jet correlations should have an increasing effect with pt
• Jet contributions should force the correlation width to approach the jet correlation width
Examine bulk correlations in different pt ranges
Most Central Amplitude vs. pt
DeSilva arXiv:0910.5938
Jets + Glasma
• Correlation strength
• f(x1,p1) jet pt range f(x2,p2) bulk associated pt range
Jet-Bulk correlation function
Hard Ridge: Jets + FlowNarrow
Wide
Jet-Bulk
Jet-Bulk width similar to E. Shuryak, Phys. Rev. C 76, 047901 (2007)
€
1
N trig
d2N
dΔφ dΔη
Hard Ridge: Flow OnlyNarrow
Bulk-Bulk
Wide
Jet-Bulk
Narrow
Jet-Bulk width similar to E. Shuryak, Phys. Rev. C 76, 047901 (2007)
€
1
N trig
d2N
dΔφ dΔη
Hard Ridge
dN/dpt constrains jet fraction• Bulk particles: Blast Wave• Jet particles: Total - BW• Jet scale Qs ; take 1.25 GeV
Jets + Flow Fit the Hard Ridge• Bulk-Bulk correlations ~70%.• Bulk-Bulk + Jet-Bulk better azimuthal agreement
Jorn Putschke, QM ‘06
The Ridge: From Soft to Hard
Bulk Correlations •Amplidude decreases with pt,min
• Narrow width from flow alone
Jet+Bulk Correlations• Jet contribution dominates with increasing pt,min
• r widening at large pt,min would indicate significant contribution from jet correlations out in the ridge
Summary
Ridge Azimuthal Width
• Flow induces angular correlations
• Azimuthal width vs. pt can distinguish flow from jets
Long Range Correlations
• Implications on particle production mechanism
Glasma + Blast Wave
• Blast Wave fixed by single particle spectra
• Glasma fixed by dN/dy and 200 GeV Au+Au
• Predicts the height and azimuthal width of the Soft and Hard Ridge
• Predict energy, centrality, system, and pt dependence
Bulk Correlations Dominate the Hard Ridge
Why Long Range Correlations?
• must originate at the earliest stages of the collision
• like super-horizon fluctuations in the Universe
• information on particle production mechanism
Dumitru, Gelis, McLerran, Venugopalan, arXiv:0804.3858
Hard vs. Soft Ridge
• N. Armesto, C.A. Salgado, U.A. Wiedemann, Phys. Rev. Lett. 93, 242301 (2004)• P. Romatschke, Phys. Rev. C 75, 014901 (2007)• A. Majumder, B. Muller, S. A. Bass, Phys. Rev. Lett. 99, 042301 (2007)• C. B. Chiu, R. C. Hwa, Phys. Rev. C 72, 034903 (2005)• C. Y. Wong, arXiv:0712.3282 [hep-ph]• R. C. Hwa, C. B. Yang, arXiv:0801.2183 [nucl-th]• T. A. Trainor, arXiv:0708.0792 [hep-ph]• A. Dumitru, Y. Nara, B. Schenke, M. Strickland, arXiv:0710.1223 [hep-ph]• E. V. Shuryak, Phys. Rev. C 76, 047901 (2007)• C. Pruneau, S. Gavin, S. Voloshin, Nucl.Phys.A802:107-121,2008
• S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97, 162302 (2006)• S. A. Voloshin, Phys. Lett. B 632, 490 (2006)• S. Gavin and G. Moschelli, arXiv:0806.4366 [nucl-th]• A. Dumitru, F. Gelis, L. McLerran and R. Venugopalan, arXiv:0804.3858 [hep-ph]• S. Gavin, L. McLerran, G. Moschelli, arXiv:0806.4718; arXiv:0910.3590 [nucl-th] • F. Gelis, T. Lappi, R. Venugopalan, arXiv:0807.1306 [hep-ph]• J. Takahashi et. al. arXiv:0902.4870 [nucl-th]
hard ridge explanations -- jet interactions with matter
soft ridge -- similar but no jet -- collective behavior
Blast Wave Single Particle Fits
fit momentum spectra in 200 GeV Au+Au
10% systematic uncertainty in scale of v and T
Akio Kiyomichi, PHENIX
0
0.2
0.4
0.6
0.8
0 100 200 300 400
0
0.1
0.2
0.3
0 100 200 300 400
62 GeV Au+Au:
5% smaller v, 10% smaller T
temperature
velocity at r = R
Npart participants
Npart
Blast Wave and the Correlation FunctionSchnedermann, Sollfrank & Heinz
• Single Particle Spectrum
A Hubble like expansion in used in a Boltzmann Distribution
• Correlation Function
Correlation Strength
strength
N
2R ≡ c(x1,x2 )
volume∫∫ =
R=
2 − μ
μ 2
1
K+
K 2 − K2
K2
K flux tubes, assume NK=μK , N2
K− N K
2 = 2K
K varies event-by-event
N 2 − N 2 = 2 K + μ2 K 2 − K 2( )N =μ K ,
= n2 (x1, x2 ) − n1(x1)n1(x2 ){ }volume∫∫ = N(N −1) − N
2
K flux tubes
R
fluctuations per tube number of tubes
Soft Ridge vs. pt
Peak Amplitude Au-Au 200 GeV
STAR preliminary
Most Central Amplitude vs. pt
• Increase the lower pt limit of the soft ridge calculation toward the hard ridge range.
• As the lower pt limit is increased less particles are available for correlations.
• Correlation amplitude for the most central collision plotted vs. the lower pt limit.
Soft Ridge vs. pt
• Higher pt particles received a larger radial push narrower relative angle.
Peak Width Au-Au 200 GeV
Most Central Width vs. pt
STAR preliminary
Angular width from
Quenching + Flow
RA
r
quenched away jet
• Survival probability
• Production probability
• Jet path
• Jet Distribution
L
E. Shuryak, Phys. Rev. C 76, 047901 (2007)
• Surviving jets tend to be more radial, due to quenching.
“Jet-Bulk” correlations
“Bulk-Bulk” correlations
Two Contributions
1E-14
1E-13
1E-12
1E-11
1E-10
1E-09
1E-08
1E-07
1E-06
1E-05
0.0001
0.001
0.01
0.1
1
10
100
1000
0 2 4 6 8 10 12
Blast Wave
Invariant Spectrum
pt
Thermal Bulk
Jets
STAR PRL vol 91, number 17 (2003)
• Both the Bulk-Bulk and Jet-Bulk contributions are weighted by the fraction of bulk or jet particles to the total.