Long range rapidity correlations in highenergy nucleus collisions at RHIC and LHC
Heavy Ion Pub @ Ohsaka University
Takahito Todoroki
University of Tsukuba & Riken Nishina Center2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

1	Outline• Overview of basic ridge property• Ridge study via Δφ correlations with respect to Reaction Plane• Triangular flow
• Δη correlations with respect to trigger η	• Ridge in high multiplicity p+p events at LHC-CMS• Summary2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

2	Long range rapidity correlations
Phys. Rev. C 80, 064912 (2009)2< pTasso < pTtrig	

2< pTasso < pTtrig	

Jet	Jet	Ridge	

• Long range rapidity correlations up to large rapidity = “Ridge”• Seen in Au+Au, absent in d+Au collisions• Superposition of jet and ridge at Δφ∼0 & Δη∼0 in Au+Au collisions	2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

3	pT spectra of Jet and Ridge yieldPhys. Rev. C 80, 064912 (2009)• Jet spectrum is increasing with pTtrig
as jet fragmentation• Ridge spectrum is softer andapproximately independent of pTtrig• Ridge is “bulk-like”
2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

4	Ridge shape gets clearer with pT

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

5	Centrality evolution of Ridge
Au+Au 200GeV data - fit (except same-side peak)pT > 0.15 GeV
83-94%

M.Daughersity, QM08, J.Phys.G35:104090,2008
55-65%

46-55%

0-5%• Rapid transition from 55-65% to 46-55%• Small change to most central after transition• Ridge may be phenomena of underlying event

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

6	Ridge and Jet Δφ correlations with respect to Reaction Plane• Jet = (|Δη|<0.7) -Accep*(|Δη|>0.7)• |Δη|>0.7 = near-side ridge + away-side• Flow subtraction by ZYAM

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

7	Ridge correlations have reaction plane dependence

1	

2	
3	
4	5

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba		

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Correlated Emission ModelChiu,Hwa, arXiv:0809.3018
Correlated Emission Model (CEM)	

in-plane
jet flowalignedmore ridge	

out-of-plane
jet flow
misaligned
less ridge	

Asymmetric ridge peak predicted	

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

9	Ridge and Jet Δφ correlations with respect to Reaction Plane••••1	2	Jet = (|Δη|<0.7) -Accep*(|Δη|>0.7)|Δη|>0.7 = near-side ridge + away-side
Flow subtraction by ZYAM
2 Gaussian fit to away side and subtracted– Ridge obtained3	4	5	6	Δφ	2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

10	Near side peak asymmetry• Jet shape is symmetric• Ridge is asymmetric!
– shift to Δφ>0 side
• Ridge may come fromjet-flow alignment2011	  Feb	  18th	3	2	4	5	6	1	

T. Todoroki, University of Tsukuba	

11	

Back to Back Ridge••••

2011	  Feb	  18th	

Jet = (|Δη|<0.7) -Accep*(|Δη|>0.7)|Δη|>0.7 = near-side ridge + away-side
Flow subtraction by ZYAM
Fit : Back-to-Back Ridge + away conical emissions

T. Todoroki, University of Tsukuba	

12	

Triangular Flow
Pictures : Alver RHIC-AGS Meeting 2010	

arXiv:0806.0513v1• Triangular flow is possible source of ridge!

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

13	Comparison of AMPT and STAR

VnΔ =	  <cos	  n(φasso - φtrig)>~	  Vn2	arXiv:1003.0194v3
2011	  Feb	  18th	

• v2 & v3 are depending on initialgeometry in AMPT• AMPT simulations have goodconsistency with data at pT >0.8GeV

T. Todoroki, University of Tsukuba	

14	S. Esumi WWND2011

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

15	Δη correlations with respect to trigger η	• Jet and Ridge property as function of trigger η	– Back/Forward asymmetry of correlation shapes– Gradient of correlation functions

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

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PYTHIA82011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

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AMPT

20	  ~	  50%	0	  ~	  20%	Flow Not Subtracted50	  ~	  93%	C2	  :	  arbitrary	  unit	

Near side : |Δφ| < π/4	Δη = ηasso- ηtrig :[-­‐4,+4]	

ηtrig =	  -­‐2.0	

2011	  Feb	  18th	

ηtrig =	  0	T. Todoroki, University of Tsukuba	

ηtrig =	  2.0	18	

PHENIX Data Analysis• Trigger “sign” selection : “η<0” and “η>0”• Precise trigger selection : [-0.35,0.35] 14bins. 0.05 step.

• Δη correlations : projected from Δφ - Δη correlations– Near side : |Δφ| < π/4	

– Away side : |Δφ - π| < π/4	• Superposition of jet and ridge due to central arm accep. |η|<0.35
2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

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Trigger η sign selected correlations

η>0	

η<0	2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

20	Projected Δη correlations : Trigger η sign selected

Near : |Δφ|<π/4	

Away: |Δφ - π|<π/4	

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

21	Near side Δη correlations : precise trigger selection

Near : |Δφ|<π/4	

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

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Away side Δη correlations : precise trigger selection

Away: |Δφ - π|<π/4	

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

23	

Backward / Forward asymmetry“Forward” : Δη>0
“Backward” : Δη<0	Centrality : 0~20
trigger (hadron): Pt 2~4GeV
ηtrig [0, 0.05]
associate (hadron) : Pt 1~2GeV

Backward

Forward• Yield Ratio = (AvgForward - AvgBackward)/(AvgForward + AvgBackward)– Forward : 0 < Δη <0.25– Backward : -0.25 < Δη <0• YR=0 : symmetric shape• YR>0 or <0 : shift for Forward or Backward direction
2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

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Backward / Forward asymmetry : trigger sign selection• Degree of asymmetry– at most 2σ in peripheral at near side
– at most 1σ in peripheral at away side2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

25	

Backward / Forward asymmetry : trigger precise selection• Large statistical & systematic error on both near and away side2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

26	

Gradient of correlations as function of trig ηCentrality : 0~20
trigger (hadron): Pt 2~4GeV
ηtrig [0, 0.05]
associate (hadron) : Pt 1~2GeVif	  ηtrig >0if	  ηtrig <0• Fitting function : [0] + [1]*x• Fitting range– Δη : [ 0,0.35] if ηtrig <0– Δη : [-0.35,0] if ηtrig <02011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

27	Gradient of correlations seems to be flat

• Gradient of correlations seems to be flat at near side
• Away side also seems to be flat though still large statistical error

2011	  Feb	  18th	T. Todoroki, University of Tsukuba	

28	

Correlations in high multiplicity p+p events at LHC-CMS
Minimum Biasno cut on multiplicity

High multiplicity data set
and N > 110

The peak is truncatedin both distributions
Back-to-back jet correlations enhanced in high multiplicity sample.
2011	  Feb	  18th	T. Todoroki, University of Tsukuba	

29	

Minimum Biasno cut on multiplicity

High multiplicity data set
and N>110

New “ridge-like” structure extending to large Δη at Δφ ~ 02011	  Feb	  18th	T. Todoroki, University of Tsukuba	

30	Data and PYTHIA82011	  Feb	  18th	T. Todoroki, University of Tsukuba	

31	Other simulation models

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

32	Data and PYTHIAD6T at 0.9, 2.36 and 7 TeVPYTHIA D6T	2011	  Feb	  18th	PT inclusive	

T. Todoroki, University of Tsukuba	

33	Comparison 7 TeV p+p and 200 GeV Cu+Cu correlations
High multiplicity data set N>110

Hard Probe 2010, Putschke	• Correlations in Cu+Cu at similar multiplicity dominated by flow.
• How correlation shape changed if v2 exists in high mult. p+p event?
• Need to survey azimuthal dynamics in high mult. p+p events

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

34	

Accumulative azimuthal correlations
STAR AuAu 200GeV	 arxiv:nucl-ex/0407007v3<Σi cos2(φtrig - φiasso)> = Mult.*v2	  (pTtrig)	  v2asso+{non-­‐ﬂow}	

0.15 < pTasso <2.0GeV/c at |η|<1.0	Trigger• Consistent with p+p minimum bias at peripheral• Enhance of Au+Au correlations at mid central & central by flowlike component• Method to search the possible modification in high multiplicity p+pevents from minimum bias because no event plane needed2011	  Feb	  18th	T. Todoroki, University of Tsukuba	

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Accumulative correlations in high multiplicity p+p events at 200 GeVMidori Kajigaya Univ. of Tsukuba	<Σi cos2(φPt - φi)> = Mult.*v2	  (pT)	  v2asso	  +	  {non-­‐ﬂow}	

• Enhance in mid-rapidity high multiplicity event• Azimuthal dynamics in p+p events depends on multiplicity if tracknumber count and calculation done in same rapidity range.
2011	  Feb	  18th	T. Todoroki, University of Tsukuba	

36	

Possible ridge in p+p collisions at RHIC energy?
CERN-ISR
Nucl. Phys. B145 (1978)
305-348	

p+p √s = 52.6 GeV
0.5< Passo• data to analyze : 500GeV, 200GeV and 62.4 GeV

2011	  Feb	  18th	T. Todoroki, University of Tsukuba	

37	Summary• Overview of basic ridge property• Ridge study via Δφ correlations with respect to Reaction Plane– Ridge depends on Reaction Plane• Triangular flow
– Possible source of ridge– AMPT well describes STAR experimental data at pT >0.8GeV• Δη correlations with respect to trigger η	– No trigger η dependence seen in PHENIX acceptance…
• Ridge in high multiplicity p+p events at LHC-CMS

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

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Back Up Slides

2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

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T. Todoroki, University of Tsukuba	

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2011	  Feb	  18th	

T. Todoroki, University of Tsukuba	

41	None trigger selected Δφ-Δη correlations

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T. Todoroki, University of Tsukuba	

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T. Todoroki, University of Tsukuba	

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