Heavy Ion Physics and Electron Ion Colliders - PowerPoint Presentation

Slide1

Heavy Ion Physics and Electron Ion Colliders

W. A. HorowitzThe Ohio State UniversityJuly 29, 2010

7/29/2010

1

EIC at CUA

With many thanks to Brian Cole,

Miklos

Gyulassy

,

Ulrich Heinz,

Jiangyong

Jia

, and Yuri

Kovchegov

Slide2

Two Major Discoveries at RHIC

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Huge low-p

T

v

2

Described by hydro with low viscosity

Huge high-

p

T

suppressionp0 RAA described by pQCD

Y.

Akiba for the PHENIX collaboration, PLB630, 2005

20-30%

Hirano et al., PRC77, 2008

Slide3

Why Are These Interesting?

Want to characterize the QGPCan’t directly measureUse indirect toolsIs QGP:Most perfect fluid ever created/studied?Can one use strongly and/or weakly coupled field theory methods?pQCD vs. AdS/CFTEnormous

influence of geometry

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Slide4

QCD: Theory of the Strong Force

Running as -b-fcn

SU(Nc = 3)

Nf

(E)Nf(RHIC) ≈ 2.5

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ALEPH, PLB284, (1992)

Griffiths Particle Physics

PDG

Slide5

What are We Interested In?

Measure many-body physics of strong forceTest & understand theory of many-body non-Abelian fields

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Long Range Plan, 2008

Slide6

HI Collisions Tool for Strong Force Physics Study

Want a consistent picture of matter produced in HI collisionsThen, want to quantify the properties of the produced matter

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Slide7

Spacetime Evolution of a HI Collision

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t = -

¥

t = 0

t = 1 fm/c

t = 3 fm/c

t = +

¥

t = 4 fm/c

Initial State

Initial Overlap

Thermalization

QGP

Hadronization

Hadron

Gas

At RHIC

Nontrivial to learn about QGP through HIC

Slide8

Methods of QCD Calculation I: Lattice

All momentaEuclidean correlators

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Long Range Plan, 2008

Kaczmarek

and

Zantow

, PRD71 (2005)

Davies et al. (HPQCD), PRL92 (2004)

Slide9

Methods of QCD Calculation II: pQCD

Any quantitySmall coupling (large momenta only)

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Jäger

et al., PRD67 (2003)

d’Enterria

, 0902.2011

(

perturbative

QCD)

Slide10

Methods III: AdS/CFT

Maldacena conjecture: SYM in d  IIB in d

+1

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All quantities

N

c

→ ∞

SYM, not QCD

Probably not good approx. for

p+p

; maybe A+A?

Applicable to condensed matter systems?

Gubser

, QM09

Slide11

Geometry and Flow

Qualitative picture:Anisotropic initial geometry => anisotropic flow7/29/2010

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Slide12

Hydrodynamics and v2

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Hydro

Early therm.

¶

m

T

mn

= 0

Equation of State (EOS)

Ideal:

h

/s = 0

v

2

: 2

nd

Fourier

coef

of particle spectrum:

Slide13

Viscous Hydrodynamics

Viscosity reduces elliptic flowNaive pQCD => h/s ~ 1Naive AdS/CFT =>

h/s ~ 1/4p

=> Strongly coupled medium?

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Luzum

and

Romatschke

,

Phys.Rev.C78:034915,2008

Shear Viscosity, Wikipedia

Slide14

Geometry in Viscosity Extraction

Poorly constrained initial geom => 100% uncertainty in viscosity

KLN CGC breaks down at edge of nuclear overlapWhole effect comes from edges!

Experimental constraints needed!

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T Hirano, et al.,

Phys.Lett.B636:299-304,2006

Slide15

Why High-pT Particles?

Tomography in medicine7/29/2010

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http://www.fas.org/irp/imint/docs/rst/Intro/Part2_26d.html

One can learn a lot from

a single probe

…

PET Scan

and even more with multiple probes

SPECT-CT Scan uses internal

g

photons and external X-rays

Slide16

Tomography in QGP

Requires well-controlled theory of:production of rare, high-pT probesg, u, d, s, c, bin-medium E-losshadronization

Requires precision measurements of decay fragments

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p

T

f

,

g

,

e

-

Invert attenuation pattern => measure medium properties

Slide17

QGP Energy Loss

Learn about E-loss mechanismMost direct probe of DOF7/29/2010EIC at CUA

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pQCD

Picture

AdS

/CFT Picture

Slide18

Common variables used are transverse momentum,

pT, and angle with respect to the reaction plane, f

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High-pT Observables

Naively

: if medium has no effect, then

R

AA

= 1

Fourier

expand

R

AA:7/29/2010

p

T

f

,

g

,

e

-

Slide19

pQCD Rad Picture

Bremsstrahlung RadiationWeakly-coupled plasmaMedium organizes into Debye-screened centersT ~ 250 MeV

, g ~ 2m ~ gT

~ 0.5 GeVl

mfp ~ 1/g2T ~ 1 fm

R

Au

~ 6 fm

1/

m

<< lmfp

<< Lmult. coh. em.7/29/2010EIC at CUA19

Bethe-

Heitlerdp

T/dt ~ -(T

3/Mq2) p

T

LPM

dp

T

/

dt

~ -LT

3

log(

p

T

/

M

q

)

Gyulassy

,

Levai

, and

Vitev

, NPB571 (200)

Slide20

EIC at CUA

20pQCD Success at RHIC:

Consistency: R

AA

(h

)~R

AA

(

p

)

Null Control: R

AA

(g)~1GLV Prediction: Theory~Data

for reasonable fixed L~5 fm and dN

g/dy~dNp/dy

Y.

Akiba for the PHENIX collaboration, PLB630, 2005

(circa 2005)

7/29/2010

Slide21

pQCD Seemingly Inadequate

Lack of even qualitative understandingp0, h, g

RAA well described, BUTe-

RAA, v2 is not, even with elastic loss

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Wicks et al.

Death of pQCD at RHIC?

pQCD assumes M << E:

b E-loss not under control

p

0

R

AA

p

0

v

2

PHENIX

p

0

9.5 GeV!

30-40% Centrality

WHDG

Slide22

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22Jets in AdS/CFT

Model heavy quark jet energy loss by embedding string in AdS space

dpT/dt = -

m pT

m

=

pl

1/2

T

2

/2MqJ Friess, S Gubser, G

Michalogiorgakis, S Pufu

, Phys Rev D75 (2007)7/29/2010

Similar to Bethe-Heitler

dpT/dt

~ -(T

3

/M

q

2

)

p

T

Very different from LPM

dp

T

/

dt

~ -LT

3

log(

p

T

/

M

q

)

Slide23

EIC at CUA

23Compared to DataString drag:

qualitative agreement

WAH

,

PhD Thesis

7/29/2010

Slide24

Light Quark and Gluon E-Loss

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WAH,

in preparation

D

L

g

therm

~ E

1/3

D

L

q

therm ~ (2E)1/3

Renk

and

Marquet

, PLB685, 2010

Slide25

High-pT and HIC Spacetime

Evolution7/29/2010EIC at CUA

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Slide26

Geometry and High-pT v2

CGC vs. KLN and rotating RPEffect not large enough

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Effects of geom. on, e.g. v

2

, might be quite large

WAH and J

Jia

,

in preparation

Need experimental constraints on initial geometry!

Slide27

Conclusions

Tantalizing physics discoveries at RHICLarge low-pT v2nearly perfect strongly coupled fluidLarge high-pT

suppressionweakly coupled quasiparticle plasmaStatement that QGP at RHIC is strongly coupled nearly ideal fluid depends sensitively on the IC

Diffuse medium and AdS/CFTSharp medium and pQCDExciting

eRHIC and LHeC HI physics opportunities

Knowledge of

r

(

b

)

extremely

important for quantitative (qualitative?) HI physics

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