Addressing the physics of the ridge by 2- and 3-particle correlations at STAR

1
Addressing the physics of the ridge by 2- and
3-particle correlations at STAR

• Pawan Kumar Netrakanti
• Purdue University
• (For STAR Collaboration)

2
Outline

• Motivation
• 2-particle correlation w.r.t. reaction plane
• AuAu 20-60 (?sNN 200GeV)
• Correlation asymmetry
• 3-particle ??-?? correlations
• dAu, AuAu 40-80 and AuAu 0-12 (?sNN200GeV)
• Charge dependence of 3-particle ??-??
  correlations
• Summary

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Ridgewhat we already know
STAR Preliminary
STAR Preliminary
AuAu 0-12
dAu
2-particle correlation shows prominent ridge
along ?? in near side (??lt0.7) Ridge
properties are similar to bulk
4
Ridge vs. Reaction Planewhat we know
Analyze trigger particles at different sides
separately.
Prediction Asym. peak
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Di-hadron ?? results
Poster220 J. Konzer

• Jet Y(??lt0.7) AcceptanceY(??gt0.7).
• ??gt0.7 ridge away-side. Two-Gaussian fit to
  away-side and subtract ? Ridge

??gt0.7
3ltpTTriglt4 GeV/c
AuAu 20-60
1ltpTAssoclt1.5 GeV/c
?S0
?S90
STAR Preliminary
?f fassoc-fTrig
?S0
?S90
STAR Preliminary
Ridge
Jet
?f fassoc-fTrig
Ridge is asymmetric in ??
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Correlation Asymmetry
Shaded Sys. Errors.

• Away-side is Asymmetric (not shown in plot)..
• Jet is symmetric.
• Ridge is asymmetric !
• Ridge asymmetry consistent with CEM -
• ridge may be due to jet-flow alignment.

Asymmetry
Chu Hwa, Lindenbaum Longacre, Voloshin,
Shuryak, McLerran ,Venugopalan Gavin
et.al Takahashi et. al.
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Ridge 3-particle ??-?? what we know
Trigger
AuAu 0-12
dAu
STAR Preliminary
A2
A1
3ltpTTriglt10 GeV/c 1ltpTAssoclt3 GeV/c ??lt0.7
P.K. Netrakanti J.Phys.G35 (2008) 104010.

• Ridge
• Approximately uniform or broadly falling with ??.
• Uniform event-by-event.

Will charge separated 3-particle ??-??
correlation help in understanding ridge ?
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Charge dependence of 3-particle correlations
3ltpTtriglt10 GeV/c 1ltpTassoclt3 GeV/c
??lt0.7
Like (T,A) or (T- A-) Unlike (T- A)
or (T A-)
STAR Preliminary

• Separate particles according to the charge
• AALike TLike ? (T A1 A2) or (T- A1-
  A2-)
• AALike TUnlike ? (T A1- A2-) or (T- A1
  A2)
• AAUnlike ? (T A1 A2-) or (T
  A1- A2) or (T- A1 A2-) or (T- A1- A2)
• Total ? No charge seperation
• The AAUnlike is obtained by ? Total
  (AALikeTLike AALikeTUnlike)
• Using charge combinations we can separate Jet
  and Ridge.

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3-particle ??-?? correlations
3ltpTtriglt10 GeV/c 1ltpTassoclt3 GeV/c
??lt0.7
dAu
AuAu 12
Charge independent (Total)
AALike (AALikeTLike AALikeTUnlike)
STAR Preliminary
AAUnlike (Total - AALike)
Ridge in all charge combinations in AuAu.
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Radial projection for correlations
STAR Preliminary
3ltpTtriglt10 GeV/c 1ltpTassoclt3 GeV/c
??lt0.7
STAR Preliminary
AALikeTLike
AAUnlike
AALikeTUnlike
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Jet and Ridge separation
Ridge (T- A) A) Ridge (T A) A) Ridge
(T A- ) A-) Ridge (T- A- ) A-)
STAR Preliminary
Ridge(AALikeTUnlike) Ridge(AALikeTLike)
AALikeTLike No Jet, only Ridge AALike Jet
Ridge
AALike TAA,T-A-A-, T-AA-
,TA-A- AAUnlike TA-A,TA-A T-A-A ,T-AA-
STAR Preliminary
3x
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3-particle ??-?? Jet and Ridge
Jet 3(AALikeTUnlike - AALikeTLike) Ridge
Total - Jet
STAR Preliminary
STAR Preliminary
Ridge is wide. No prominent substructures in
ridge.
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Summary

• Di hadron ??
• New data on dihadron w.r.t. RP.
• Jet is symmetric. Ridge is asymmetric.
• 3-particle ??-??
• Jet and Ridge are separated by charge
  dependence.
• Jet is narrow. Ridge is wide in ?.
• Color flux tubes Flow ?

? Flow effect
? Initial state effect
Thank you