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The long-range pseudo-rapidity correlations in high-energy collisions 王王王 Purdue University

The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

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Page 1: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

The long-range pseudo-rapidity correlations in high-energy collisions

王福强Purdue University

Page 2: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

Proton, neutron, meson (hadron)Quark Gluon Plasma (QGP)

The Big Bang and the Little Bang

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Page 3: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

Nuclear Phase Diagram

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Page 4: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

Heavy-Ion Collisions simulationHadron cascade

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Page 5: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

CMSSTAR

ALICE

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PHENIX

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Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL)

STAR and PHENIX experiments

New York BNL- RHIC

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Two types of discoveries

• Theoretically predicted, and experimentally verified, e.g.– J/Y– W, Z bosons

• Surprises, e.g.– Parity violation– Microwave background radiationLong-range pseudo-rapidity correlations

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Page 8: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

Variables, observables

g = 100

13 fm

STAR: Solenoidal Tracker At RHICy

x

f

1ln

2

ln tan2

z

z

p p

p p

qz

ppT

pz

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Page 9: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

x

y z

coordinate space anisotropy

py

px

momentum space anisotropy

Hydrodynamic bulk collectivity, elliptic flow

- 0 p p fparticle-FR.P. (rad)

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Page 10: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

Collective expansion of QGP- elliptic (2nd order) and higher order event anisotropic collectivity and its Nquark scaling - hydro-dynamic properties of QGP

PHENIX Preliminary, QM12

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Page 11: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

Elliptic expansion during the partonic (quark-gluon) phaseHadron formation via quark recombination / coalescence

Hadron

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Page 12: The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

jet

p p

Au Au

Energy loss (jet quenching) in QGP

Phys. Rev. Lett. 91, 072304 (2003) PRL109, 152302 (2012)arXiv: 1208.2254

central Au+Au

gq

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Novel phenomena in heavy-ions

• Double-peak away-side correlations• Odd harmonics• Long-range ridge correlations• Ridge in small systems• …

Au+Au ridge

Df Dh

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Jet Correlations

Jet event in e+e- collision STAR Au+Au collision

Jet produces high pT particles Select a high pT particle to trigger on jet.NB: trigger = off-line trigger

Df

trigger particlepT > 3 GeV/c

associatedparticle

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Dihadron correlationsSTAR, PRL 95 (2005); PRC82 (2010)

STAR, PRL91 (2003)

• Clear evidence of jet-quenching, and it’s a final-state effect

• Low pT enhancement and broadening• Away-side double peak; Large-Dh small-Df

ridge correlation• v2 subtracted but not higher harmonics

Away-side

triggerjet

0 p1-1 Df

pTtrig=4-6 GeV/c

pTassoc=0.15-4 GeV/c

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Relative to the Event Plane

• Ep-dep correl

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v2max {2,hgap=0.7}

v2max{2,hgap=0.7}, v3{2,hgap=0.7}

STAR, arXiv:1010.0690v1Todoroki (PHENIX) 1304.2852Trigger

Associated

Df

EPfS

• Evolution of structure seems to remain from in-plan to out-of-plane.• Single away-side peak in-plane, double-peak out-of-plane.• Jet interactions with QGP medium. Physics mechanisms?

|Dh| > 0.7

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Three-particle correlations

• v2 and v4 subtracted.

• Does v3 remove all of the off-diag. peak strength? Need further study.

• Deflected jets contributions (to diag. peaks) must be present.

• Need to be followed up with v3 subtraction.

7/1/2013

Δ1

Trigger

Δ2

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Df

trigger particlepT > 3 GeV/c

assoc. particlepT =1-2 GeV/c

d+Au

Au+Au ridge

Df Dh

The longitudinal ridge

h ~ 1h ~ 0

trigger particlepT > 3 GeV/c

Dh

assoc. particlepT =1-3 GeV/c

||

<0.7

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Ridge vs trigger anglev2

max {2,hgap=0.7}

v2max{2,hgap=0.7}, v3{2,hgap=0.7}

Df Dh7/1/2013

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Ridge yield vs trigger anglev2

max {2,hgap=0.7}

v2max{2,hgap=0.7}, v3{2,hgap=0.7}

Subtractv3

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LHC-CMS

usual p-p collision high multiplicity p-p collision

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Ridge in small systems

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• Why wasn’t it discovered long ago by HEP?

• Two types of discoveries: – Theoretically predicted, and experimentally verified– Surprises

• HEP moved on to more exclusive processes

• There may be still important physics that were missed in last half century.

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p-p collision (high Mul.)p-Pb collision (high Mul.)

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Physical origin unclear

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CGC/Glasma

Dusling & Venugopalan 1211.3701

Dusling and Venugopalan, arXiv:1302.7018

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Another explanation: Hydro flow• In heavy-ions, large Dh small Df correlations:

subtract v2 non-zero finite correlation (ridge)

• In pp, pA, dA systems, large Dh small Df correlations:subtract flat pedestal non-zero finite correlation (ridge)

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d+Au ridge?

• Jet contribution within PHENIX acceptance• LHC+RHIC more stringent test on theoretical models.

7/1/2013

PHENIX, arXiv:1303.1794

1.25-1.5 GeV/c

Bozek, PRC85 (2012)

PHENIX acceptance

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Straight differenceNo ZYAM involved

STAR PRELIMINARY STAR PRELIMINARY

Df projections in different Dh (TPC mult. |h|<1 as centrality)

• ZYAM syst. error from different sizes of Df region for ZYAM.• Efficiency corrected: 85 ± 5% .

0.15 < pTtrig < 3 GeV/c, 1 < pT

assoc < 2 GeV/c

ZYAM-edSTAR PRELIMINARY STAR PRELIMINARY

ZYAM-edSTAR PRELIMINARY

ZYAM-ed

STAR PRELIMINARY

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Dh projections in different Df (TPC mult. |h|<1 as centrality)

• ZYAM syst. error from different sizes of Df region for ZYAM.• Efficiency corrected: 85 ± 5% .

STAR PRELIMINARY STAR PRELIMINARY

ZYAM-edSTAR PRELIMINARY

ZYAM-edSTAR PRELIMINARY

0.15 < pTtrig < 3 GeV/c

1 < pTassoc < 2 GeV/c

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Central – Peripheral

• ZYAM syst. error from different sizes of Df region for ZYAM.• Efficiency corrected: 85 ± 5% .

0.15 < pTtrig < 3 GeV/c, 1 < pT

assoc < 2 GeV/c

FTPC 0-20% - 40-100%

STAR PRELIMINARY

TPC 0-20% - 50-80%

STAR PRELIMINARY

TPC 0-20% - 50-80%

STAR PRELIMINARY

TPC 0-20% - 50-80%

STAR PRELIMINARY

Minimalridge

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Very forward correlations

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TPC-FTPC correlations

Dh triangle acceptance

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Sanity check

4 23 20

2( .) 2acc

3 22 20

2( .) 1acc

3 20.5 5

2( .) 1acc

PHOBOS, PRC 72 (2005) 031901(R)

TPC-FTPC

TPC-TPC

All charged hadrons

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ZYAM’ed Dh Correlations(TPC mult. as centrality)

Discontinuity because it’s Dh not h distribution.At Dh=2, TPC-TPC and TPC-FTPC pairs come form different h’s.

Raw correl.

ZYAM’ed

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Fourier fit results

TPC-TPC Au-side TPC-TPC d-side

TPC-FTPC d-sideTPC-FTPC Au-side

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Fourier fit results (replot of previous slide)

Summary• Correlations have v1 and v2 components• v1 appears ~1/N. v2 ~constant over multiplicity• Even at very forward d-side, v2 component is large (maybe even larger than Au-

side).• Not sure what the data mean.

Au-side d-side

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Conclusions

• Particle correlations in heavy-ions– Novel phenomenon of v3– After v3 subtraction, features of jet-medium

interactions remain

• Ridge in small systems– Intriguing– May contain important physics

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The question of v1

• In the pt=1-2 GeV/c region, directed flow fluctuation effect may be negligible.

Pandit (STAR), arXiv:1211.7162

7/1/2013

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Have to rethink about inclusive dihadron• We have used so far <vt{2}*va{2}>=<vt{2}>*<va{2}>. This is OK because fluctuations

are already included in v{2}.• However, if v{2} depends on slice, then <vt{2}slice*va{2}slice><vt{2}slice>*<va{2}slice>.

• <vt{2}slice*va{2} slice> = (vt{2}1*va{2}1 + vt{2}6*va{2}6)/2 = (vt{2}1*va{2}1 + vt{2}6*va{2}1 - vt{2}6*va{2}1 + vt{2}6*va{2}6)/2 = <vt{2}>*va{2}1 - vt{2}6* (va{2}1 - va{2}6)/2 > <vt{2}>*va{2}1 which is the maximum.

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ZYAM’ed Dh Correlations(ZDC as centrality)

7/1/2013