Is the QGP produced in LHC collisions more opaque than that produced in RHIC collisions?

Is the QGP produced in LHC collisions more opaque than that produced in

RHIC collisions?Roy A. Lacey

Chemistry Dept., Stony Brook University

1 Erice 2012, Roy A. Lacey, Stony Brook University

p

Conjectured Phase Diagram

2

Quantitative study of the QCD phase diagram is central to our field

Erice 2012, Roy A. Lacey, Stony Brook University

Interest

Location of the critical End point

Location of phase coexistence lines

Properties of each phaseAll are fundamental to the

phase diagram of any substanceSpectacular achievement:Validation of the crossover transition leading to the QGP

Full characterization of the QGP is a central theme at RHIC and the LHC

Characterization of the QGP produced in RHIC and LHC collisions requires:

I. Development of experimental constraints to map the topological, thermodynamic and transport coefficients

II. Development of quantitative model descriptions of these properties

QGP Characterization?

Erice 2012, Roy A. Lacey, Stony Brook University3

ˆ( ), ( ), ( ), ( ), ( ), ( ), (B), etc ?s s sepT c T T T T q T

Experimental Access: Temp/time-averaged

constraints as a function of √sNN (with similar expansion dynamics)

(I) Expect space-time averages to evolve with √sNN

ˆ, , , , , , etc ?s sT c qs s

(II)

4

RHIC (0.2 TeV) LHC (2.76 TeV) Power law dependence (n ~ 0.2) increase ~ 3.3 Multiplicity density increase ~ 2.3 <Temp> increase ~ 30%

The energy density lever arm Lacey et. al, Phys.Rev.Lett.98:092301,2007

Essential questions: How do the transport coefficients evolve with T?

Any indication for a change in coupling close to To?

ˆ, , ,s sc qs


Energy scan

Take home message:The scaling properties of flow andJet quenching measurements give crucial new insights

The Flow Probe

s/

P ² Bj

, , /s, f, Ts fc

20

3

1 1

~ 5 45

TBj

dER dyGeVfm

5

( ) 1 2 cosn nYield a v n

Idealized Geometry

2 2

2 2

y x

y x

Crucial parametersActual collision profiles are not smooth,

due to fluctuations!Initial Geometry characterized by many

shape harmonics (εn) drive vn

Initial eccentricity (and its attendant fluctuations) εn drive momentum anisotropy vn with specific scaling properties

22, exp 03

tT t k k Ts T

Acoustic viscous modulation of vn

Staig & Shuryak arXiv:1008.3139

Isotropic p

Anisotropic p


Yield() =2 v2 cos[2(2]

KET & scaling validated for vn Partonic flow

/2n

qn

6

vn PID scalingFlow is partonic @ RHIC



Flow increases from RHIC to LHC Sensitivity to EOS increase in <cs>

Proton flow blueshifted [hydro prediction] Role of radial flowRole of hadronic re-

scattering?

Flow increases from RHIC to LHC

8

Flow is partonic @ the LHC

Scaling for partonic flow validated after accounting for proton blueshift

Larger partonic flow at the LHC

KET (GeV)

0.5 1.0 1.5 0.5 1.0 1.5 0.5 1.0 1.5

10-20%

0.5 1.0 1.50.00

0.05

0.10

0.1520-30% 30-40% 40-50%

0.5 1.0 1.5

v 2/nq

0.00

0.05

0.10

0.15

Kp

Pb+Pb @ 2.76 TeV 05-10%


Hydrodynamic flow is acoustic

Characteristic n2 viscous damping for harmonics Crucial constraint for η/s

Associate k with harmonic n nkR


2 gR n

Note: the hydrodynamic response to the initial geometry [alone] is included

εn drive momentum anisotropy vn with modulation

22, exp 03

tT t k k Ts T

Modulation Acoustic

2expn

n

v n

Constraint for η/s & δf

Deformation nkR

10

2

0

2

, exp 0

Particle Dist. ( )

( ) ~

T

TT

f

T t k n T

f f f p

pf pT

Characteristic pT dependence of β reflects the influence of δf and η/s pT (GeV/c)

0 1 2 3 (

p T)0.00

0.05

0.10

0.15

0.20

0.25

0.30

4s = 1.25(pT)-1/2

4s = 0.04s = 1.25 f~pT

1.5

20-30%Hydro - Schenke et al.


ATLAS-CONF-2011-074

11

High precision double differential Measurements are pervasiveDo they scale?


vn(ψn) Measurements - ATLAS

Acoustic Constraint

Characteristic viscous dampingof the harmonics validatedImportant constraint

Wave numbernkR

12

2 gR n LHCRHIC

2expn

n

v n

1~4s


arXiv:1105.3782

at RHIC; small increase for LHC

22, exp 03

tT t k k Ts T

http://arxiv.org/abs/arXiv:1105.3782


2 4 6

v n/n

0.01

0.1

1 10-20%

n2 4 6

20-30%

2 4 6

30-40%

2 4 6

v n/n

0.01

0.1

140-50%Pb+Pb - 2.76 TeV

pT = 1.1 GeV/c

Acoustic Scaling 2expn

n

v n

β is essentially independent of centrality for a broad centrality range

15 30 45

0.00

0.05

0.10

0.15

0.20

0.25

pT = 1.1 GeV/c

Pb+Pb - 2.76 TeV

Centrality (%)

14

2 4 6

v n/n

0.01

0.1

1

0.7 GeV/c

n2 4 6

1.3 GeV/c

2 4 6

1.9 GeV/c

2 4 6

v n/ n

0.01

0.1

1

2.3 GeV/cPb+Pb - 2.76 TeV

20-30%

2expn

n

v n

β scales as 1/√pT Important constraint


Constraint for η/s & δf

<η/s> ~ 1/4π at RHIC; small increase for LHC

Scaling properties of Jet Quenching

Erice 2012, Roy A. Lacey, Stony Brook University 15


Jet suppression Probe

AAAA

binary AA pp

YieldR ( , )N YieldTp L

2( , ) [1 2 ( )cos(2 )]T TYield p v p

2

AA 20

AA 2

(90 , ) 1 2 ( )( , )(0 , ) 1 2 ( )

oT T

TT T

R p v pR p LR p v p

Suppression (∆L) – pp yield unnecessary

Jet suppression drives RAA & azimuthal anisotropy with specific scaling properties

Suppression (L)

, Phys.Lett.B519:199-206,2001

For Radiative Energy loss:

0

LcIT eI

Modified jet

Moresuppression

Lesssuppression

Fixed Geometry

Path length(related to collision

centrality)

17

Geometric Quantities for scaling

A B

Geometric fluctuations included Geometric quantities constrained by multiplicity density.

~L RL R

*cosn nn

Phys. Rev. C 81, 061901(R) (2010)

arXiv:1203.3605

σx & σy RMS widths of density distribution


RAA Measurements - CMS

Specific pT and centrality dependencies – Do they scale?

18

Eur. Phys. J. C (2012) 72:1945 arXiv:1202.2554

Centralitydependence

pT dependence


L scaling of Jet Quenching - LHC

RAA scales with L, slopes (SL) encodes info on αs and qCompatible with the dominance of radiative energy loss

19

arXiv:1202.5537

ˆ

, Phys.Lett.B519:199-206,2001


20

Phys.Rev.C80:051901,2009


L scaling of Jet Quenching - RHIC

RAA scales with L, slopes (SL) encodes info on αs and qCompatible with the dominance of radiative energy loss

ˆ

RAA scales as 1/√pT ; slopes (SpT) encode info on αs and q L and 1/√pT scaling single universal curveCompatible with the dominance of radiative energy loss

21

arXiv:1202.5537

pT scaling of Jet Quenching

ˆ

, Phys.Lett.B519:199-206,2001


High-pT v2 measurements - CMS


22

arXiv:1204.1850

pT dependence

Centralitydependence




0 5 10

v 2

0.00

0.05

0.10

0.15

0.20

0.25

10 - 20%

Au+Au @ 0.2 TeV

pT (GeV/c)0 5 10

20 - 30%

0 5 100.00

0.05

0.10

0.15

0.20

0.2530 - 40%

High-pT v2 measurements - PHENIX

pT dependence

Centrality dependence

24

High-pT v2 scaling - LHC

v2 follows the pT dependence observed for jet quenchingNote the expected inversion of the 1/√pT dependence

arXiv:1203.3605


pT-1/2 (GeV/c)-1/2

0.2 0.3 0.4 0.5

v 2

0.0

0.1

0.2

10 - 20 (%)20 - 3030 - 40

0.2 0.3 0.4 0.5

v 2/L

(fm-1

)

0.0

0.2

0.4

Au+Au @ 0.2 TeV

25

∆L Scaling of high-pT v2 – LHC & RHIC

Combined ∆L and 1/√pT scaling single universal curve for v2

arXiv:1203.3605


Npart

0 100 200 300

v 2/L

0.0

0.5

v 2

0.0

0.1

0.2 6 < pT < 9 (GeV/c)pT > 9

pT-1/2 (GeV/c)-1/2

0.2 0.4 0.6

v 2/L

0.0

0.2

0.4

10 - 20 (%)20 - 3030 - 40

Au+Au @ 0.2 TeV


∆L Scaling of high-pT v2 - RHIC

Combined ∆L and 1/√pT scaling single universal curve for v2

Constraint for εn

(pTJet)-1/2 (GeV/c)-1/2

0.05 0.10 0.15

v 2Jet

0.00

0.05

0.10

10-20 (%)20-30 30-40 40-50

Pb+Pb @ 2.76 TeV

27

Jet v2 scaling - LHC

v2 for reconstructed Jets follows the pT dependence for jet quenchingSimilar magnitude and trend for Jet and hadron v2 after scaling


pT-1/2 (GeV/c)-1/2

0.1 0.2 0.3

v 2

-0.05

0.00

0.05

0.10

0.15Jet - ATLASHadron - CMS

pT-1/2 (GeV/c)-1/2

0.1 0.2 0.3

v 2

-0.05

0.00

0.05

0.10

0.15Jet - ATLASHadrons - CMSHadrons - scaled (z ~ .62)

ATLAS

28

Jet suppression from high-pT v2

Jet suppression obtained directly from pT dependence of v2

arXiv:1203.3605

2( , ) [1 2 ( )cos(2 )]T TN p v p

2

AA 20

AA 2

(90 , ) 1 2 ( )( , )(0 , ) 1 2 ( )

oT T

v TT T

R p v pR p LR p v p

Rv2 scales as 1/√pT , slopes encodes info on αs and q̂


0.2 0.4

ln(R

2)

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.210 - 20%

pT-1/2 (GeV/c)-1/2

0.2 0.4

20 - 30%

0.2 0.4

30 - 40%

pT-1/2 (GeV/c)-1/2

0.2 0.4

ln(R

2)/

L [fm

-1]

-2.0

-1.5

-1.0

-0.5

0.0

0.5

10 - 20 (%)20 - 3030 - 40

Au+Au @ 0.2 TeV


Jet suppression from high-pT v2 - RHIC2

AA 20

AA 2

(90 , ) 1 2 ( )( , )(0 , ) 1 2 ( )

oT T

v TT T

R p v pR p LR p v p

Jet suppression obtained directly from pT dependence of v2

R2 scales as 1/√pT , slopes encodes info on αs and ˆq

L (fm)0.5 1.0 1.5 2.0

ln(R

AA)

-1.5

-1.0

-0.5

0.0D (prompt)6 - 12 GeV/c

Pb+Pb @ 2.76 TeV

ALICE

Consistent obtained


qLHC ˆ

Heavy quark suppression

31

Extracted stopping power

2

ˆ ~ 0.75 RHICGeVqfm

Phys.Rev.C80:051901,2009

2

ˆ ~ 0.56 LHCGeVqfm

obtained from high-pT v2 and RAA [same αs] similar - medium produced in LHC collisions less opaque!

arXiv:1202.5537 arXiv:1203.3605

Conclusion similar to those of Liao, Betz, Horowitz, Stronger coupling near Tc?

qRHIC > qLHCˆqLHC ˆ


Remarkable scaling have been observed for both Flow and Jet Quenching

They lend profound mechanistic insights, as well as New constraints forestimates of the transport and thermodynamic coefficients!

32

RAA and high-pT azimuthal anisotropy stem from the same energy loss mechanism

Energy loss is dominantly radiative

RAA and anisotropy measurements give consistent estimates for <ˆq >

RAA for D’s give consistent estimates for <ˆq >

The QGP created in LHC collisions is less opaque than that produced at RHIC

Flow is acousticFlow is pressure driven Obeys the dispersion relation

for sound propagation Flow is partonic

exhibits scalingConstraints for:

initial geometry η/s similar at LHC and RHIC ~

1/4π

What do we learn?

/2 n, 2, /2

vv ( ) ~ v or ( )

nn q T q n

q

KEn

Summary


End

33Erice 2012, Roy A. Lacey, Stony Brook University

34

Flow @ RHIC and the LHC


Multiplicity-weighted PIDed flow results reproduce inclusive charged hadron flow

results at RHIC and LHC respectively

Charge hadron flow similar @ RHIC & LHC


For partonic flow, quark number scaling expected single curve for identified particle species vn

Is flow partonic?

/2 n2 /2

vExpectation: v ( ) ~ v or ( )

nn T n

q

KEn Note species dependence for all vn

Is the QGP produced in LHC collisions more opaque than that produced in RHIC collisions?

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