TWO PARTICLE CORRELATION MEASUREMENTS AT PHENIX

Takahito Todoroki For the PHENIX CollaborationUniversity of Tsukuba & RIKEN Nishina Center

Hard Probes 2012 at Cagliari, Italy

28 May 2012 Hard Probes 2012 1

Contents•Higher harmonic event plane and flow(vn)•Correlations with vn subtractions•Correlations relative to event plane

-At high and intermediate pT

•Summary

28 May 2012 Hard Probes 2012 2

Motivations•Dissect possible interplay of hard-scattered partons & hot dense medium

•To have definitive answer what remains in correlations after vn subtractions

•To test path length dependence of parton energy loss via correlations relative to event plane

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Initial state of collisions

• Initial collision geometry- Smooth to Fluctuating picture

• Azimuthal particle distribution- vn(even){F2} only ⟶ vn(even){Fn} + vn(odd) {Fn}

Smooth picture Fluctuating picture

F2

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• v3 is comparable to v2 at 0~10%• v2 evolution as centrality increment, no evolution in v3 • v4{F4} ~ 2 x v4{F2}

Charged particle vn : ||<0.35Event plane Fn : ||=1.0~2.8

PRL.107.252301

Charged Hadron vn at PHENIX28 May 2012 Hard Probes 2012 5

Identified Particle vn

• Mass dependence at low pT : Hydrodynamics• Baryon/Meson diff. at mid pT: Quark Coalescence

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vn contributions in correlations

• Contributions from vn :• Ridge & Shoulder positions : Agree with v3 peaks• vn subtractions needed to get real jet correlations

Ridge

2< pTasso < pT

trig GeV/C

Phys. Rev. C 80, 064912 (2009)Phys. Rev. C 78, 014901 (2008)

○:p+p●: Au+Au

Shoulder

v2 subtracted

n=3 n=3

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Correlations with D gap

•vn reproduce Ridge & Shoulder at 0-5%

Track at ||<2.5 with EP from full FCAL 3.3<||<4.8

vn with EP Method

vn with 2Par. Cor Method Charged particle pair with large rapidity gap e.g. |D|>2

Pb+Pb 2.76TeV

No

Flow

Sub

trac

tion

￮ measured correlations

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QM’11 J. Jia ATLAS Flow Plenary

Correlations without D gap

•Away side shoulders are almost gone in most-central collisions 0-20%

Incl.g - hadron2-3x1-2 GeV/c

PHENIX PRELIMINARY Au+Au 200GeV 0-20%

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|D|<0.7

Correlations up to centrality 50%

• Away side shoulders - Canceled in most-central collisions : 0-10%- Remain in mid-central collisions : 20-50%

• To Do : Include v1 term to vn modulation for definitive answer

V2, V3 & V4(F4) modulationby ZYAM method

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Correlations relative to event plane

•Control parton path length-By selecting trigger relative to forward event plane

-Reduce autocorrelations of jet itself

ft

fa

Df

Fn

fs

Mid rapidity Forward rapidity

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High pT range

•Near side yield : No suppression•Away side yield : Monotonic decrease

I AA =

YA

A/Y

ppShort path

lengthLong path

length

PRC.84.024904

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v2 & v4{F2} modulatedAu+Au 200GeV 20-60%

Intermediate pT range

•Constant suppression of back-to-back jet•Two competitive effects seen

F2 R.P. F2 R.P.

Trig.

Trig.

Trig.

Trig.

in-plane trigger case

out-of-plane trigger case

Au+Au 200GeV 20-50%h-h :2-4x1-2GeV/cv2 & v4{F2} modulated

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PHENIX preliminary

Flow subtracted yield is shown radially with base line.

penetration dominancesurface dominance

Summary• Higher harmonic flow vn has been measured• By vn modulation to correlations,

- Shoulders almost gone in most-central collisions

- Shoulders remain in mid-central collisions• Correlations relative to event plane

- Monotonic away side suppression at high pT

- Constant suppression of di-jet & Two competitive effects at intermediate pT

• Fully vn modulated analyses are in progress

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Backup Slides

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Fi - Fj correlations 28 May 2012 Hard Probes 2012 16

PRL.107.252301

vn via event plane method

•Mid rapidity particle anisotropy relative to forward event planes

0 5-5

ZDC/SMD

dN/d

RXN in: 1.5<||<2.8 & out: 1.0<||<1.5

MPC: 3.1<||<3.7

BBC: 3.0<||<3.9

CNT: ||<0.35

2cm Pb converter in front

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RXN

Degeneracy among models disentangled by v3

• v3 seems to prefer low viscosity- Glauber+4p/s =1 works better

- CGC-KLN+4p/s =2 failed

• More constraints to hydrodynamics calculations

V2

V3

PRL.107.252301 (ppg132)B. Alver et. al., PRC82, 034913(2010).B. Schenke et. al., PRL106, 042301(2011).H. Petersen et. al., PRC82, 041901(2010).

(Event Plane Method)

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QM’11 J. Jia ATLAS Flow Plenary

Scaling property of v2

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Scaling property of vn

•vn(KET/nq)/nq failed on v3, v4 & v4{F2}•vn(KET/nq)/nq

n/2 : need correction power

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Fourier decomposition of flow subtracted correlations

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Correlations relative to F3

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