The Ridge in pp, pA and AAheinz/JET2013/lecture... · Normalization term to go from correlation amplitude to yield per trigger particle for some measurements: also v4 6. Gunther Roland

Gunther Roland JET summer school

The Ridge in pp, pA and AA

Gunther Roland

1


Jet-Medium interactions• General belief that HI collisions produce a

“medium”– hydro-like azimuthal correlations and spectra– modification of strongly interacting hard probes

• Missing link– response of the medium to excitation, i.e. jets

• Search for jet-medium interactions/correlations• Is there a medium if it doesn’t respond to

excitations?• Use track-track and jet-track correlations as tool to

study jet-medium interactions

2


Angular Correlation Functions

9

Signal distribution

Same event pairs

Background distribution:

Mixed event pairs

€

Δη =η1 −η2

Δϕ =ϕ1 −ϕ 2pT-inclusive two-particle

angular correlation function

CMS 7TeV pp min bias, pT > 0.1 GeV/c

Ratio Signal/Background

3


High(er) pT Correlations in pp

“Near-side” (Δφ ~ 0) jet peak:

Correlation of particles within a single jet

“Away-side” (Δφ ~ π) jet correlations:

Correlation of particles between back-to-back jets

1 < pT < 3 GeV/c

Dominated by jet-like correlations

CMS 7TeV pp min bias

Momentum conservation:~ -cos(Δφ)

4


AMPT 2.8TeV PbPb min bias

High(er) pT Correlations in PbPb

PbPb correlations, 1 < pT < 3 GeV/c Large v2 term dominates correlations

Note: flow modulation in correlation function is ∝vN2

Hydrodynamic Flow

5


“Flow subtraction”

v2 subtracted “associated yield”

“ZYAM” (zero yield at minimum): assume that one component of the correlations (jets) gives zero contribution at some Δϕ; match v2 flow at

that Δϕ and subtract

“Raw” correlation function

= { ]a(Δη- +

Normalization term to go from

correlation amplitude to yield per trigger particle

for some measurements: also v4

6


Selected Results

pTtrig : 3-4 , pTassoc : 0.4-1 GeV/c

PHENIX, PRC 78, 014901 (2008)

pTtrig : 4 - 6 GeV/cpTassoc : 2 - 4 GeV/c

“Disappearance” of away-side jet correlations in central AuAu

Broadening of away-side jet correlations in central AuAu:

Conical emission?

STAR, J.Phys.G34:S679-684,2007pTtrig : 3-4 , pTassoc : >2 GeV/c

Emergence of long-range near-side correlations in AuAu: Ridge

pTtrig : >2.5 , pTassoc : >0 GeV/c

PHOBOS, PRL.104:062301 (2010)

STAR, PRL 91, 072304 (2003)

7

Ridge, Bulk, and Medium Response How to Kill Models and Learn Something in the Process

Jamie NagleUniversity of Colorado at Boulder

π0

p-p 200 GeV

Ridgeology

Bulkeology

MediumologyBulleologyQM 20098

Ridge, Bulk, and Medium Response How to Kill Models and Learn Something in the Process

Jamie NagleUniversity of Colorado at Boulder

Ridgeology

Bulkeology

MediumologyBulleologyQM 20098

Medium Response?

“The Ridge” Basic Properties:

1. pT spectra similar to bulk (or slightly harder)

2. baryon/meson enhancement similar to bulk

3. Scales per trigger like Npart similar to bulk

Ridge is 1-3% on top of Bulk

See talk by J. Chen

“Theoretical Free-For-All” Paul Stankus

“Theorists, help us Kill your model.”

Brian Cole QM08

QM 2009

9

Δη

Trigger pT = 3 …12 GeVAssoc pT = 2 … 4 GeV

pt,assoc. > 2 GeVSTAR preliminary

yiel

d(Δφ)

in Δη

win

dow

Ridge

Jet

Δη window center

PHOBOS Preliminary

Trigger pT > 2.5 GeVAssoc pT > 0.035 GeV

ηΔφΔ

STAR Preliminary


“Soft Ridge” “Just Right Ridge”

QM 2009 10

Δη

Trigger pT = 3 …12 GeVAssoc pT = 2 … 4 GeV

pt,assoc. > 2 GeVSTAR preliminary

yiel

d(Δφ)

in Δη

win

dow

Ridge

Jet

Δη window center

PHOBOS Preliminary


ηΔφΔ

STAR Preliminary


“Hard Ridge” “Soft Ridge” “Just Right Ridge”

QM 2009 10

Mach Cone Dream

QM 2009 11

φ = -900

Wave Energy at Circle Boundary Mach Cone Dream

QM 2009 11

φ = -900

Wave Energy at Circle Boundary Mach Cone Dream

QM 2009 11

φ = -900

Wave Energy at Circle Boundary

θΜ = 1.37 ± 0.02 (stat.)± 0.06 (syst.)

φ = +900

Mach Cone DreamPHENIX arXiv:0801.4545

d+Au Au+Au central

STAR, PRL102:052302,2009

PERFECT FLUID RESPONSE!QM 2009 11

φ = -900

Wave Energy at Circle Boundary

Pb-Au 17.3 GeV 0-5%

CERESPreliminary

Time to Wake Up

θΜ = 1.37 ± 0.02 (stat.)± 0.06 (syst.)

φ = +900

Mach Cone DreamPHENIX arXiv:0801.4545

d+Au Au+Au central

STAR, PRL102:052302,2009

PERFECT FLUID RESPONSE!QM 2009 11

Pruneau, Gavin, Voloshin, arXiv:0711.1991v2

Dijet and then simple boost in one direction (to demonstrate)

arXiv:0902.4870v1, J. Takahashi et al.QM 2009 12



arXiv:0902.4870v1, J. Takahashi et al.

Again, NEXUS + SPHERIO

QM 2009 12





QM 2009 12





QM 2009 12





QM 2009 12





These soft physics pictures also need to be elevated to realistic full space-time and to confront the full data sets….

QM 2009 12






Including v1, v2, v3, v4 and fluctuations in these quantitiesQM 2009 12






Including v1, v2, v3, v4 and fluctuations in these quantitiesQM 2009 12






Including v1, v2, v3, v4 and fluctuations in these quantitiesAlso, see Poster P. SorensenQM 2009 12


Demise of ridge and mach cones

13


ψ2

Nuclei consist of finite number of

protons and neutrons

Hama et al, 2000Miller, Snellings,

2003PHOBOS coll.,

2005

Re-thinking initial conditions

Nucleus I

Nucleus II

14


ψ2

Nuclei consist of finite number of

protons and neutrons

Hama et al, 2000Miller, Snellings,

2003PHOBOS coll.,

2005

Re-thinking initial conditions

Nucleus I

Nucleus II

vs

14


Initial Geometry Fluctuations

ψ2

Participant Eccentricity

PHOBOS PRL 98, 242302 (2007)

PHOBOS PRL 104, 142301 (2010)

PHOBOS PRC81, 034915 (2010)

€

ε =r2 cos(2φ( )

2+ r2 sin(2φ( )

2

r2

15


arXiv:0806.0513 PRL 104, 06230 (2010)

pT1,pT2 > 0.8 GeV/c

(before v2 subtraction)

pT1> 0.05 GeV/c,pT2> 2.5 GeV/c

Existing data are well described by v1,v2,v3,v4

v3 component seen in published data

16


Triangular Flow

17


Triangularity...

18


Participant Triangularity

ψ3

€

ε3 =r2 cos(3φ( )

2+ r2 sin(3φ( )

2

r2

Burak Alver, GR, arXiv:1003.0194 (PRC in press)

Triangular flow from shape fluctuations

19


Participant Triangularity

ψ3

€

ε3 =r2 cos(3φ( )

2+ r2 sin(3φ( )

2

r2

Burak Alver, GR, arXiv:1003.0194 (PRC in press)

Just like elliptic flow reflects event-by-event eccentricity,“triangular flow” (v3) reflects

event-by-event “triangularity” (ε3)

Triangular flow from shape fluctuations

19


ψ3

ψ2

€

v2 = cos 2(φ −ψ2)( ) ∝ε

€

v3 = cos 3(φ −ψ3)( ) ∝ε3

Hacked version of AMPT showed same connection between ε3 and v3 as for ε2 and v2

Elliptic and triangular flow in AMPT

20


Add v22 and v32

Δφ Δη

ψ2è

~ v22 cos(2Δφ)

ΔφΔη

≈

≈

ψ3 è

2-particle correlation function

“Ridge” + “mach cones”

Elliptic flow (v2)

Triangular flow (v3) fromfluctuating initial condition

21


First confirmation in ideal hydro

Higher order components in data~20 talks at recent

Quark Matter 2011 conference

Single calculation describes Fourier coefficients at RHIC and LHC

(small change in η/s from RHIC to LHC)

Prediction from experiment confirmed by theory

Bjoern Schenke

Higher Fourier components in hydroAlver, Gombeaud,Luzum,Ollitrault Phys.Rev. C82 (2010) 034913

22

http://inspirehep.net/author/Alver%2C%20Burak%20Han?recid=863740&ln=en

http://inspirehep.net/author/Alver%2C%20Burak%20Han?recid=863740&ln=en

http://inspirehep.net/author/Gombeaud%2C%20Clement?recid=863740&ln=en

http://inspirehep.net/author/Gombeaud%2C%20Clement?recid=863740&ln=en

http://inspirehep.net/author/Luzum%2C%20Matthew?recid=863740&ln=en

http://inspirehep.net/author/Luzum%2C%20Matthew?recid=863740&ln=en

http://inspirehep.net/author/Ollitrault%2C%20Jean-Yves?recid=863740&ln=en

http://inspirehep.net/author/Ollitrault%2C%20Jean-Yves?recid=863740&ln=en


2010

23


Return

of the

Ridge

2010

24


High multiplicity events in pp

22

Level-1:Require ET> 60 GeV

in calorimeters

High-Level trigger:Count number of tracks with pT > 0.4 GeV/c, |η| < 2, within dz < 0.12cm of a single vertex with z <10cm

Dedicated trigger needed to record highest multiplicities

25


High Multiplicity Trigger

Two different HLT thresholds: Nonline > 70 and Nonline > 85

HLT85 trigger range un-prescaledfor full 980nb-1

out of 5x1010 collisions

Multiplicity binning usespT > 0.4 GeV/c

|Δη| < 2.4

26


Results

24

Inclusive pT

MinBias high multiplicity (N>110)

Jet peak/away-side correlations enhanced in high multiplicity events

Abundant jet production in high multiplicity sample27


Inclusive pT

MinBias high multiplicity (N>110)

Results

25

Cut off peak at (0,0): Shows structure of away-side ridge (back-to-back jets)

Small change for large δη around δφ ~ 0 ?28


Results

26

Pronounced structure at large δη around δφ ~ 0 !

Intermediate pT: 1-3 GeV/cMinBias high multiplicity (N>110)

Figure 7

29

DESY Seminar November 8 2010

Interpretation

• Search for long-range correlations in pp was motivated by results in AuAu collisions at RHIC– AuAu correlations believed to result from QGP hydro flow

• CMS found long-range correlations in high multiplicity pp events– Some aspects of pp correlations resemble those in AuAu

41

This does not mean that we have discovered QGP production in pp collisions

30

Gunther Roland JET summer school11

Two-Particle Correlations in 7TeV pp

High multiplicity (N>110)

Interpretation:

Multi-jet correlationsJet-Jet color connectionsJet-proton remnant color

connectionsJet-remnant connections + medium

Glasma correlationsQuantum entanglement

Angular momentum conservationAngular momentum conservation +

mediumHydrodynamic flow

Multiplicity in these events is dominated by jet contribution.

31


Study pPb as a func/on of mul/plicity

N=235 event

p Pb

32


Mul.plicity Evolu.on in pPb

Divide into 4 mul/plicity bins:

Ntrkoffline

p Pb

Low multiplicity

33



06/09/13 Dragos Velicanu

Ntrkoffline

p Pb

Increasing multiplicity


34


Mul.plicity Evolu.on in pPbp Pb



35



Ntrkoffline

p Pb



36

(GeV/c)T

p0 2 4 6

Asso

ciat

ed Y

ield

/ (G

eV/c

)

0.00

0.02

0.04 110≥ offline

trkNCMS(a)

= 5.02 TeVNNspPb

= 7 TeVspp

offlinetrkN

0 50 100 150As

soci

ated

Yie

ld /

(GeV

/c)

0.00

0.02

0.04 < 2 GeV/c

T1 < p(b)


Ridge Associated YieldIn the pT range where

the yield is the strongest, the ridge

turns on at N≈40

In the signal (N>110) region, the strength of

the effect rises and falls with pT

ZYAM example

37


Dussling, Venugopalan (arXiv:1211.3701v1)

Initial state “Glasma” 4-gluon

correlations

Bozek, Broniowski(arXiv:1211.0845)

Hydrodynamics in pPb

assume formation of an equilibrated system

Initial state effects or hydro medium?

838


From Ridge to Double-RidgeATLAS

ALICE

Phys. Rev. Lett. 110, 182302 (2013)

Physics Letters B 719 (2013) 29–41

39


Peripheral subtraction

Away side yield in pp and peripheral pPb is very similar

(away-side jet)

Assume constant contribution vs centrality and subtract

ALICE

40


Fourier components in pPb

Peripheral subtraction allows extraction of Fourier coefficients vs pT and centrality

Should these be interpreted as flow?

41


4-particle correlations

Strong flow-like signal also seen in 4-particle cumulants

42

(rad)φΔ0 0.5 1 1.5 2 2.5 3

) φΔ

Y(Δ

), φΔ

Y(

-0.4-0.2

00.20.40.60.8

11.21.41.61.8

-310×

[0.75,1.0] GeV/c⊗[0.5,0.75] [0.48,0.7]∈| ηΔ = 200 GeV |NNsd+Au

0-5%cY 50-88%pY

p-YcY = YΔ))φΔcos(2

2(1+2a0a

0-5%cY 50-88%pY


2(1+2a0a


PHENIX dAu correlations

Centrality difference is well-described by cos(2Δφ)

Y (��) ⌘ 1

N t

dNpairs

d�� bZYAM

43


PHENIX dAu correlations

0.0 0.5 1.0 1.5 2.0 2.5 3.0

[0.5,0.75] GeV/c⊗[0.5,0.75] 0-5%cY 50-88%pY


2(1+2a0a

0-5%cY 50-88%pY


2(1+2a0a

(a)

-410×8

6

4

2

0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

[1.5,2.0] GeV/c⊗[0.5,0.75]

(c)

76543210

-1

0.0 0.5 1.0 1.5 2.0 2.5 3.0

[1.0,1.25] GeV/c⊗[0.5,0.75] = 200 GeVNNsd+Au

[0.48,0.7]∈| ηΔ |

(b)

-410×10

8

6

4

2

0

-2

0.5 1.0 1.5 2.0 2.5 3.0

[2.0,2.5] GeV/c⊗[0.5,0.75]

(d)

3

2

1

0

(rad)φΔ

)φΔ

Y(Δ

), φΔ

Y(

Similar results in multiple pT bins

44


dAu (RHIC) vs pPb (LHC)

(GeV/c)T±hp

0.5 1.0 1.5 2.0 2.5 3.0 3.5

2v

0.00

0.05

0.10

0.15

0.20

0.25

0.30 [0.48,0.7]∈|ηΔPHENIX, 200 GeV, d+Au, 0-5%, | [2,5]∈|ηΔATLAS, 5.02 TeV, p+Pb, 0-2%, | [0.48,0.7]∈|ηΔPHENIX, 200 GeV, d+Au, 0-5%, |

[2,5]∈|ηΔATLAS, 5.02 TeV, p+Pb, 0-2%, |

d+Au 200 GeVp+Pb 4.4 TeV

P. Bozek:

c2�ptT, p

aT

�= v2

�ptT

�⇥ v2 (p

aT)

Hydro: Bozek, PRC 85,014911 (2012)

PHENIX, arXiv:1303.1794

Larger v2 in dAu reflecting different geometry?

45


Rapidity dependence in dAu

Significant forward/backward difference

46


Correlations in high multiplicity pPb

19

n.b., particles are counted for pT > 0.4GeV/c, |η| < 2.4

PbPb

pPb

47


pPb vs PbPb

PbPb and pPb using same multiplicity selection, 220 < N < 260

n.b., particles are counted for pT > 0.4GeV/c, |η| < 2.5

PbPb pPb

48

Gunther Roland JET summer school 21

pPb vs PbPb: pT dependencePbPb

pPb

|Δη| > 2

|Δη| < 1

|Δη| > 2

|Δη| < 1

49


Multiplicity dependence

22

“Long-range” associated yield:Similar multiplicity dependence

for pPb and PbPb

Difference in absolute yield

“Jet” yield:Nearly identical for pPb and PbPb

pPb

PbPb

PbPb

pPb

50


4th order cumulants in multiplicity bins

Wide bins

Narrow bins + averaging

Cumulant analysis in bins of multiplicityNeed to consider bin widths carefully

CMS analysis: (narrow bins + averaging)

51


v2 in pPb and PbPb

v2 shows similar shape in pPb and PbPb, but is smaller in pPbv2{4} is only 20% smaller than v2{2} below 2 GeV/c

“Peripheral subtraction” has small effect at high multiplicity

Dash-dot line: peripheral subtracted

PbPb

pPb

multiplicity

52


v2 in pPb and PbPb

v2 smaller in pPb than PbPb

v2{4} drops at low multiplicity

“Peripheral subtraction” has small effect at high multiplicity

PbPb pPb

53


v2 in pPb and PbPb

PbPb pPb

“Fluctuations” larger in pPb,

with moderate multiplicity

dependence

54


v2 comparison with ATLAS in pPb

Subtract Ntrkoffline<20 (70-100%) to avoid removing signal

• ATLAS subtract 50-100%; forward-calorimeter centralitySome difference vs ATLAS in v2{4}: multiplicity fluctuations?

ATLAS: arXiv:1303.2084

pPb

55


v3 in pPb and PbPb

v3 has similar shape in pPb and PbPb; magnitude comparable

“Peripheral subtraction” makes essentially no differenceHydro prediction: Bozek, v3{PP}, not including fluctuations

Dash-dot line: peripheral subtracted

PbPb

pPb

multiplicity

56


v3 in pPb and PbPb

v3 shows similar shape in pPb and PbPb; magnitude comparable

“Peripheral subtraction” makes essentially no difference

pPbPbPb

57


Triangular flow in pPb vs PbPb

“similar” or “same”?

58



Summary• Ridge in AA

– Search for jet-medium interactions led to revolution in understanding of hydrodynamic flow

• Ridge in pp, pPb, dAu– many signs point to common origin of (double-) ridge in

all systems (eg. v2{4}, v3 pT and multiplicity dependence

• Is this a triumph of hydro or cause for concern?– Large v3{2} in pPb (comparable to PbPb)

• How can we identify the medium response?

3060


v3 in pPb compared to hydro

multiplicity

pPb

Perfect liquid (η/s = 1/4π) in pPb collisions?

Schenke et al

Bozek

61

Documents

The Ridge in pp, pA and AAheinz/JET2013/lecture... · Normalization term to go from correlation amplitude to yield per trigger particle for some measurements: also v4 6. Gunther Roland