Transcript Long Range Correlations and The Soft Ridge

Long Range Correlations
and The Soft Ridge
George Moschelli
Wayne State University
25th Winter Workshop
on Nuclear Dynamics
Outline:
• Correlation Measurements
Based on work with:
• PHOBOS
• STAR
Sean Gavin
• CGC + Correlations
&
• Flux Tubes
Larry McLerran
• Glasma
• Qs Dependence
arXiv:0806.4718
[nucl-th]
• Blast Wave + Correlations
• Transverse Flow
• Glasma + Flow
• Comparison to STAR
PHOBOS: High pt Triggered Ridge
from Edward Wenger, RHIC & AGS User’s Meeting, ‘08
PHOBOS: High pt Triggered Ridge
from Edward Wenger, RHIC & AGS User’s Meeting, ‘08
PHOBOS: High pt Triggered Ridge
from Edward Wenger, RHIC & AGS User’s Meeting, ‘08
long range
correlations
PHOBOS: Untriggered Ridge
from Edward Wenger, RHIC & AGS User’s Meeting, ‘08
• soft ridge with very long range in rapidity?
• caution: v2 not yet removed
Long Range Correlations
from Raju Venugopalan, RHIC & AGS User’s Meeting, ‘08
• must originate at the earliest stages of the collision
• like super-horizon fluctuations in the Universe
• information on particle production mechanism
STAR: Soft Ridge
from Lanny Ray, RHIC & AGS User’s Meeting, ‘08
Peak η Width
Peak Amplitude
peripheral
near side peak
Peak φ Width
central
Medium range correlations…implications for long range?
• v2 and experimental effects subtracted
• peak height and azimuthal width
• not the rapidity width -- structure too narrow
Gavin + Abdel-Aziz; Gavin + Pokharel + Moschelli
Hard vs. Soft Ridge
hard ridge explanations -- jet interactions with matter
• 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
soft ridge -- similar but no jet -- collective behavior
• 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 [nucl-th]
• F. Gelis, T. Lappi, R. Venugopalan, arXiv:0807.1306 [hep-ph]
Flux Tubes and Glasma
• Flux Tubes: longitudinal fields early on
• Tubesquarks+gluons
• Correlated Particles
come from the same tube
Cross sectional
slices are the same
• Causally disconnected
Large 
Flux Tubes and Glasma
• Single flux tube: phase space density of gluons
• Flux tube transverse size
• Number of flux tubes
•Gluon rapidity density
Kharzeev & Nardi:
Flux Tubes and the Correlation Function
pair density n2
single particle density n1
• Correlation function:
Assume:
• Partons from the same tube are correlated
• Correlations between tubes are negligible
correlation strength
flux tube transverse size
~ Qs-1 << RA
Correlation Strength
• Correlation Strength
• Long range glasma fluctuations
scale the phase space density
Dumitru, Gelis, McLerran & Venugopalan;
Gavin, McLerran & Moschelli
• Energy and centrality dependence
of correlation strength
Flow and Azimuthal Correlations
Fireball cross section at freeze out
STAR soft ridge
from Lanny Ray, RHIC & AGS User’s Meeting, ‘08
r
Fluid cells
• Mean flow depends on position
• Opening angle for each fluid
element depends on r
Blast Wave and Correlation Function
Schnedermann, Sollfrank & Heinz
• Single Particle Spectrum
• Boltzmann Distribution
• Cooper Frye Freeze Out Surface
• Pair Spectrum
Blast Wave and Correlation Function
• Correlation Function
Glasma + Blast Wave
STAR measures:
• v and T from Blast Wave
Akio Kiyomichi, PHENIX
• Scaled to fit 200 GeV
We calculate:
Peak Amplitude 200 GeV
1
0.8
Blast Wave (with correlations)
0.6
0.4
• Glasma Qs dependence
0.2
200GeV62GeV
0
STAR 200 GeV
1
2
3
4
5
6
Glasma Energy Dependence
• v and T from Blast Wave
Akio Kiyomichi, PHENIX
• Scaled to fit 200 GeV
• Glasma Qs dependence
200GeV62GeV
Angular Correlations
0.6
• Fit using Gaussian + offset
0.4
0.2
0
0
• Range:
0.5
1
1.5
2
Peak  Width
• Error band: 20% shift
in fit range
computed angular width is approximately independent of energy
Summary
Long Range Correlation Measurements
• PHOBOS: may extend to large rapidity
• STAR: measurements in a smaller range
Blast Wave + Glasma
• Describes amplitude and azimuthal width
• Glasma energy and centrality dependence