Electromagnetic probes of the Electromagnetic probes of the QGP - - PowerPoint PPT Presentation

SLIDE 1

Electromagnetic probes of the Electromagnetic probes of the QGP QGP

E Elena lena Bratkovskaya Bratkovskaya

Institut f Institut fü ür Theoretische Physik r Theoretische Physik & FIAS, & FIAS,

• Uni. Frankfurt
• Uni. Frankfurt

BLTP, BLTP, 3 September, 2014 3 September, 2014

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Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 2

Electromagnetic probes: photons and dileptons Electromagnetic probes: photons and dileptons

• Advantages:

Advantages:

• dileptons and real photons are

dileptons and real photons are emitted from different stages of the emitted from different stages of the reaction and not effected by final reaction and not effected by final-

• state interactions

state interactions

• provide undistorted information

provide undistorted information about their production channels about their production channels

• promising signal of QGP

promising signal of QGP – – ‚ ‚thermal thermal‘ ‘ photons and dileptons photons and dileptons

• Disadvantages:

Disadvantages:

• low emission rate

low emission rate

• production from hadronic corona

production from hadronic corona

• many production sources which

many production sources which cannot be individually cannot be individually disentangled by experimental data disentangled by experimental data

• Requires

Requires theoretical models theoretical models which describe the which describe the dynamics dynamics

• f heavy
• f heavy-
• ion collisions during

ion collisions during the whole time evolution! the whole time evolution!

Feinberg (76), Shuryak (78)

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Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 3

Dynamical models for HIC Dynamical models for HIC

Macroscopic Macroscopic Microscopic Microscopic ‚ ‚Hybrid Hybrid‘ ‘ (Macro+Micro) (Macro+Micro)

• QGP phase:

QGP phase: hydro hydro with QGP EoS with QGP EoS

• hadronic freeze

hadronic freeze-

• out: after burner
• ut: after burner -
• hadron

hadron-

• string transport model

string transport model

( (‚ ‚hybrid hybrid‘ ‘-

• UrQMD, EPOS,

UrQMD, EPOS, … …) )

fireball fireball models: models:

• no explicit dynamics:

no explicit dynamics: parametrized time parametrized time evolution evolution (TAMU)

(TAMU)

ideal ideal

(Jyv (Jyvä äskyl skylä ä,SHASTA, ,SHASTA, TAMU, TAMU, … …) )

Non Non-

• equilibrium microscopic transport models

equilibrium microscopic transport models – – based on many based on many-

• body theory

body theory

Hadron Hadron-

• string

string models models

(UrQMD, IQMD, HSD, (UrQMD, IQMD, HSD, QGSM, GiBUU, QGSM, GiBUU, … …) )

Partonic cascades Partonic cascades pQCD based pQCD based

(Duke, BAMPS, (Duke, BAMPS, … …) )

Parton Parton-

• hadron models:

hadron models:

• QGP:

QGP: pQCD pQCD based cascade based cascade

• massless q, g

massless q, g

• hadronization: coalescence

hadronization: coalescence

(AMPT, (AMPT, HIJING HIJING) )

• QGP:

QGP: lQCD EoS lQCD EoS

• massive quasi

massive quasi-

• particles

particles (q and g with spectral functions) (q and g with spectral functions) in self in self-

• generated mean

generated mean-

• field

field

• dynamical hadronization

dynamical hadronization

• HG: off

HG: off-

• shell dynamics

shell dynamics ! ! applicable for strongly applicable for strongly interacting systems interacting systems ! !

viscous viscous

(Romatschke, (2+1)D VISH2+1, (Romatschke, (2+1)D VISH2+1, (3+1)D MUSIC, (3+1)D MUSIC,… …) )

hydro hydro-

• models:

models:

• description of QGP and hadronic phase

description of QGP and hadronic phase by hydrodynamical equations for the fluid by hydrodynamical equations for the fluid

• assumption of local equilibrium

assumption of local equilibrium

• EoS with phase transition from QGP to HG

EoS with phase transition from QGP to HG

• initial conditions (e

initial conditions (e-

• b

b-

• e, fluctuating)

e, fluctuating)

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Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 4

• Hadron phase:

Hadron phase: using using VDM VDM: : Ι Ι Ι Ι Ι Ι Ι Ιm mΠ Π Π Π Π Π Π Π ~> ~> Ι Ι Ι Ι Ι Ι Ι ΙmD mDρ

ρ ρ ρ ρ ρ ρ ρ in

in-

• medium

medium ρ ρ ρ ρ ρ ρ ρ ρ-

• meson spectral function

meson spectral function from many from many-

• body approach

body approach ( cf.

( cf. Rapp, Chanfrey, Wambach, NPA 617 Rapp, Chanfrey, Wambach, NPA 617 ( (1997) 472 ) 1997) 472 )

Modeling of photon/dilepton emission Modeling of photon/dilepton emission

I.

• I. Emission rate

Emission rate from from thermal field theory thermal field theory: :

Feinberg Feinberg (76), (76), McLerran McLerran, , Toimela Toimela (85) (85), , Weldon (90), Weldon (90), Gale, Gale, Kapusta Kapusta (91) (91)

,T) f(q ) | q | (q Π Im π) 2 ( g q d R d q

ν 3 ν 3 3

• =

= = = − − − − = = = =

,T) f(q ) q , (q Π Im L q 1 π) 2 ( e 2 p d p d R d E E

ν 4 6 2 3 3 3

• µ ν

µ ν µ ν µ ν

= = = =

− − − − + + + + − − − − + + + +

• Photons:

Photons:

• Dileptons:

Dileptons:

1 e 1 ,T) f(q

T / q

− − − − = = = =

• Bose distribution:

Bose distribution:

• L

Lµν

µν µν µν µν µν µν µν is the electromagnetic leptonic tensor

is the electromagnetic leptonic tensor

• Π

Π Π Π Π Π Π Πµν

µν µν µν µν µν µν µν is the

is the retarded photon self energy retarded photon self energy at finite T : at finite T :

T ipx 4

)] ( J ), x ( J [ e x d i ~ > > > > < < < <

∫ ∫ ∫ ∫

ν ν ν ν µ µ µ µ µ ν µ ν µ ν µ ν

Π Π Π Π

3 q 3 4

σ π 4 T q d x d dR q = = = =

→ → → →

• Rates at q

Rates at q0

• 0 are related to electric

0 are related to electric conductivity conductivity σ σ σ σ σ σ σ σ0

• Probe of

Probe of electric properties of the QGP electric properties of the QGP

PHSD plot from Cassing et al., PRL 110 (2013) 182301; PHSD plot from Cassing et al., PRL 110 (2013) 182301;

• cf. also NJL: Marty et al., PRC87 (2013)
• cf. also NJL: Marty et al., PRC87 (2013) 3, 034912

3, 034912; ; poster by R.Marty QM poster by R.Marty QM‘ ‘14 14

PRL 110 (2013) 182301 PRL 110 (2013) 182301

• s

study of the tudy of the in in-

• medium properties of hadrons

medium properties of hadrons at high baryon density and T at high baryon density and T

• restoration

restoration of chiral symmetry (

• f chiral symmetry (ρ

ρ ρ ρ ρ ρ ρ ρ-

• a

a1

1):

): Ι Ι Ι Ι Ι Ι Ι ΙmD mDρ

ρ ρ ρ ρ ρ ρ ρ ~> chiral condensate (by

~> chiral condensate (by Weinberg sum Weinberg sum rules) rules)

(cf. Hohler, Rapp, arXiv: (cf. Hohler, Rapp, arXiv:1311.2921 1311.2921) )

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Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 5

• Modeling of hadronic elementary reactions

Modeling of hadronic elementary reactions: : Chiral models, OBE models, Chiral models, OBE models,… … (Born (Born-

• type diagrams)

type diagrams)

• Problems:

Problems:

• very

very limited experimental information limited experimental information on mm, mB elementary reactions

• n mm, mB elementary reactions
• Hadrons change their properties in the hot and dense medium:

Hadrons change their properties in the hot and dense medium:

• from vacuum cross sections to

from vacuum cross sections to in in-

• medium

medium, i.e. , i.e. from from ‚ ‚T T-

• matrix

matrix‘ ‘ to to ‚ ‚G G-

• matrix

matrix‘ ‘ approaches (many approaches (many-

• body theory)

body theory) E.g. : E.g. : ρ ρ ρ ρ ρ ρ ρ ρ-

• meson collisional broadening

meson collisional broadening – – important for dilepton studies! important for dilepton studies!

Modeling of photon/dilepton emission Modeling of photon/dilepton emission

• f(E)

f(E) -

• distribution function

distribution function

II.

• II. Emission rate

Emission rate from from relativistic kinetic theory relativistic kinetic theory: : (e.g. for 1+2 (e.g. for 1+2

• γ+3)

γ+3) γ+3) γ+3) γ+3) γ+3) γ+3) γ+3)

3 3 2 1 2 3 2 1 4 4 3 3 3 3 2 3 2 3 1 3 1 3 3 3

) 2 ( 2 )] E ( f 1 )[ E ( f ) E ( f | M | ) q p p p ( ) 2 ( E ) 2 ( 2 p d E ) 2 ( 2 p d E ) 2 ( 2 p d q d R d q π π π π δ δ δ δ π π π π π π π π π π π π π π π π ± ± ± ± × × × × − − − − − − − − + + + + = = = = ∫

∫ ∫ ∫

• Μ

Μ Μ Μ Μ Μ Μ Μ –

– invariant invariant scattering matrix element scattering matrix element from microscopic models from microscopic models Applicable also for Applicable also for non non-

• equilibrium

equilibrium system ! system !

SLIDE 6

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 6

Production sources of photons in p+p and A+A Production sources of photons in p+p and A+A

• Decay photons

Decay photons (in pp and AA):

(in pp and AA): m m

• γ

γ γ γ γ γ γ γ + X, m = + X, m = π π π π π π π π0

0, η, ω, η

, η, ω, η , η, ω, η , η, ω, η , η, ω, η , η, ω, η , η, ω, η , η, ω, η‘ ‘, a , a1

1,

, … …

• Direct photons:

Direct photons: (inclusive(=total)

(inclusive(=total) – – decay) decay) – – measured experimentally measured experimentally

• hard photons

hard photons: :

(large p (large pT

T,

, in pp and AA) in pp and AA)

• thermal photons

thermal photons: :

(low p (low pT

T, in AA)

, in AA)

• jet

jet-

• γ

γ γ γ γ γ γ γ-

• conversion

conversion in plasma in plasma

(large p (large pT

T, in AA)

, in AA)

• jet

jet-

• medium photons

medium photons

(large p (large pT

T, in AA)

, in AA) -

• scattering of

scattering of hard partons with thermalized hard partons with thermalized partons q partons qhard

hard+g

+gQGP

QGP

• γ

γ γ γ γ γ γ γ+q +q , , q qhard

hard+

+qbarQGP

QGP

• γ

γ γ γ γ γ γ γ+q +q

• QGP

QGP

• Hadron gas

Hadron gas

• prompt

prompt (pQCD; initial hard N+N scattering)

(pQCD; initial hard N+N scattering)

• jet fragmentation

jet fragmentation (pQCD; qq, gq bremsstrahlung)

(pQCD; qq, gq bremsstrahlung) (in AA can be modified by parton energy loss in medium) (in AA can be modified by parton energy loss in medium)

hard hard soft soft

PHENIX PHENIX

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Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 7

Production sources of thermal photons Production sources of thermal photons

• Thermal QGP:

Thermal QGP:

Compton scattering Compton scattering q q-

• qbar annihilation

qbar annihilation

• Hadronic sources:

Hadronic sources: (1) (1) secondary mesonic interactions:

secondary mesonic interactions: π π+ +π π ρ ρ + +γ, ρ+π γ, ρ+π π+γ, π+γ, π π+K +K ρ ρ + +γ, γ, … …

(2) (2) meson

meson-

• meson and meson

meson and meson-

• baryon

baryon bremsstrahlung: bremsstrahlung: m+m m+m m+m+ m+m+γ, γ, m+B m+B m+B+ m+B+γ , γ , m= m=π,η,ρ,ω,Κ,Κ π,η,ρ,ω,Κ,Κ*, *,… … , B=p, , B=p,∆ ∆, ,… …

HG rates (1) used in hydro ( HG rates (1) used in hydro (‘ ‘TRG TRG’ ’ model) model) -

• massive Yang

massive Yang-

• Mills approach:

Mills approach:

Turbide Turbide, Rapp , Rapp, , Gale, PRC 69, 014903 (2004) Gale, PRC 69, 014903 (2004)

HTL program ( HTL program (Klimov Klimov (1981), Weldon (1982), (1981), Weldon (1982), Braaten Braaten & & Pisarski Pisarski (1990); (1990); Frenkel Frenkel & Taylor & Taylor (1990) (1990), , … …) )

• pQCD

pQCD LO: LO: ‘ ‘AMY AMY’ ’ Arnold, Moore,

Arnold, Moore, Yaffe Yaffe, , JHEP 12, 009 (2001) JHEP 12, 009 (2001)

        QGP rates u

QGP rates used sed in in hydro hydro ! !

• pQCD NLO:

pQCD NLO:

Gale, G Gale, Ghiglieri higlieri (2014) (2014)

Models: Models: chiral chiral models, OBE, SPA models, OBE, SPA … …

Kapusta Kapusta, Gale, , Gale, Haglin Haglin (91), Rapp (07) (91), Rapp (07), , … …

• Rates

Rates beyond beyond pQCD pQCD: :

• ff
• ff-
• shell massive q, g

shell massive q, g (used in PHSD) (used in PHSD)

O.

• O. Linnyk

Linnyk, JPG 38 (2011) 025105 , JPG 38 (2011) 025105 HG (1)+ HG (1)+ ‘ ‘Baryons Baryons’ ’

+ soft + soft … …

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Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 8

2010: Direct photon spectra for Au+Au at s 2010: Direct photon spectra for Au+Au at s1/2

1/2=200 GeV

=200 GeV

PHENIX, PHENIX, Phys.

• Phys. Rev. C81 (2010) 034911
• Rev. C81 (2010) 034911

M Models

• dels:

: assume formation of a hot assume formation of a hot QGP QGP with with initial temperature initial temperature T Tinit

init at

at thermalization time thermalization time τ τ τ τ τ τ τ τ0

• Huge variations in

Huge variations in T Tinit

init and

and τ τ τ τ τ τ τ τ0

0!

! Warning: some model evolution Warning: some model evolution was was not fitted to the final hadron spectra! not fitted to the final hadron spectra! Variety of model predictions: Variety of model predictions: fireball, 2+1 Bjorken hydro, 3+1 ideal hydro fireball, 2+1 Bjorken hydro, 3+1 ideal hydro with different initial conditions and EoS with different initial conditions and EoS

• Photon spectra show sensitivity to the dynamical evolution!

Photon spectra show sensitivity to the dynamical evolution!

SLIDE 9

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 9

PHENIX: Photon v PHENIX: Photon v2

2 puzzle

puzzle

• PHENIX

PHENIX (also now ALICE): (also now ALICE): strong elliptic flow of photons strong elliptic flow of photons v v2

2(

(γ γ γ γ γ γ γ γdir

dir)~

)~ v v2

2(

(π π π π π π π π) )

• Result from a variety of

Result from a variety of models: models: v v2

2(

(γ γ γ γ γ γ γ γdir

dir) <<

) << v v2

2(

(π π π π π π π π) )

• Problem:

Problem: QGP radiation occurs at QGP radiation occurs at early times early times when when flow is not yet developed flow is not yet developed

• expected

expected v v2

2(

(γ γ γ γ γ γ γ γQGP

QGP)

)

• v

v2

2 =

= weighted average weighted average

• a large QGP contribution

a large QGP contribution gives small gives small v v2

2(

(γ γ γ γ γ γ γ γQGP

QGP)

)

Linnyk et al., PRC 88 (2013) 034904 Linnyk et al., PRC 88 (2013) 034904

PHENIX PHENIX

Challenge for theory Challenge for theory – – to describe spectra, v to describe spectra, v2

2, v

, v3

3 simultaneously

simultaneously ! !

• NEW

NEW (QM (QM’ ’2014): 2014): PHENI PHENIX, ALICE X, ALICE experiments experiments -

• large photon v

large photon v3

3 !

!

∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

⋅ ⋅ ⋅ ⋅ = = = =

i i i i 2 i 2

N v N v

SLIDE 10

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 10

• 1. Hydro: Influence of e
• 1. Hydro: Influence of e-
• b

b-

• e fluctuating initial conditions

e fluctuating initial conditions

R R. . Chatterjee Chatterjee et al. et al., , PR PRC C 88, 034901 (2013) 88, 034901 (2013)

• Jyv

Jyvä äskyl skylä ä ideal hydro ideal hydro

• Fluctuating initial conditions:

Fluctuating initial conditions: slight increase at high p slight increase at high pT

T for yield and v

for yield and v2

2

small effect, right direction! small effect, right direction!

• Ideal QGP and HG fluid

Ideal QGP and HG fluid

• Initial:

Initial: ‚ ‚bumpy bumpy‘ ‘ ebe ebe MC Glauber MC Glauber

• EoS: lQCD

EoS: lQCD

• From smooth Glauber initial conditions

From smooth Glauber initial conditions to to event event-

• by

by-

• event hydro with fluctuating initial conditions

event hydro with fluctuating initial conditions

SLIDE 11

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 11

• 2. From ideal to viscous hydro:
• 2. From ideal to viscous hydro: direct photons as a QGP

direct photons as a QGP viscometer viscometer? ?

• (2+1)D VISH2+1 (Ohio State) :

(2+1)D VISH2+1 (Ohio State) :

C C. . Shen Shen et al., et al., arXiv arXiv:1308.2111 :1308.2111, arXiv:1403.7558 , arXiv:1403.7558

• viscous QGP and HG fluid

viscous QGP and HG fluid

• Initial:

Initial: ‚ ‚bumpy bumpy‘ ‘ ebe from MC Glauber /KLN ebe from MC Glauber /KLN

• EoS: lQCD

EoS: lQCD equilibrium contribution equilibrium contribution first order viscous correction first order viscous correction

T The thermal photon emission rates he thermal photon emission rates with with viscous corrections viscous corrections: :

• Effect of s

Effect of shear hear viscos viscosity: ity: * small enhancement of the photon yield * small enhancement of the photon yield * * suppression of photon v suppression of photon v2

2

* effect on v * effect on v2

2 for photons is stronger than for hadrons

for photons is stronger than for hadrons

Thermal photons: Thermal photons: QGP +HG QGP +HG RHIC energy RHIC energy

• (3+1)D MUSIC (McGill):

(3+1)D MUSIC (McGill):

• M. Dion et al., PRC84 (2011) 064901
• M. Dion et al., PRC84 (2011) 064901
• viscous QGP and HG fluid

viscous QGP and HG fluid

• Initial:

Initial: ‚ ‚bumpy bumpy‘ ‘ ebe from IP ebe from IP-

• Glasma

Glasma

• EoS: lQCD

EoS: lQCD

Important! Important!

SLIDE 12

• (3+1)D MUSIC

(3+1)D MUSIC -

• 2014:

2014:

J J-

• F. Paquet et al. (2014
• F. Paquet et al. (2014)

)

• viscous QGP and HG fluid (

viscous QGP and HG fluid (η η η η η η η η/s=0.22) /s=0.22)

• Initial:

Initial: ‚ ‚bumpy bumpy‘ ‘ ebe from IP ebe from IP-

• Glasma

Glasma

• generate initial flow due to fluctuations of IC

generate initial flow due to fluctuations of IC

• EoS: lQCD

EoS: lQCD

• QGP photon rate: AMY

QGP photon rate: AMY

• HG photon rate: TGR for meson gas with viscous

HG photon rate: TGR for meson gas with viscous corrections + Rapp spectral function for corrections + Rapp spectral function for ρ ρ ρ ρ ρ ρ ρ ρ-

• mesons

mesons to account for the baryonic contributions to account for the baryonic contributions

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 12

• 3. Influence of Glasma initial conditions with initial flow
• 3. Influence of Glasma initial conditions with initial flow

ALICE (preliminary) ALICE (preliminary) Au+Au, Au+Au, 2760 2760 GeV GeV

• MUSIC with IC

MUSIC with IC-

• Glasma

Glasma describes describes hadronic hadronic flow flow v vn

n systematics

systematics at at RHIC & LHC RHIC & LHC, , h however,

• wever, missing v

missing v2,

2, v

v3

3 of photons

• f photons!

!

• ‚

‚Bumpy Bumpy‘ ‘ ebe from IP ebe from IP-

• Glasma

Glasma -

• small effect

small effect

IP IP-

• Glasma:

Glasma:

Schenke et al., PRL Schenke et al., PRL108 108 ( (2012) 252301 2012) 252301

SLIDE 13

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 13

• 4. Hydro with pre
• 4. Hydro with pre-
• equilibrium flow

equilibrium flow

• pre

pre-

• equilibrium flow

equilibrium flow in (2+1)D VISH2+1 in (2+1)D VISH2+1 -

• 2014:

2014:

C C. . Shen Shen et al., et al., arXiv arXiv:1308.2111 :1308.2111, arXiv:1403.7558; Talk by , arXiv:1403.7558; Talk by C.

• C. Shen

Shen @ QM @ QM‘ ‘2014 2014

• viscous

viscous QGP and HG fluid ( QGP and HG fluid (η η η η η η η η/s=0.18) /s=0.18)

• Initial:

Initial: ‚ ‚bumpy bumpy‘ ‘ ebe from MC Glauber /KLN ebe from MC Glauber /KLN

• EoS: lQCD

EoS: lQCD

• QGP photon rate: AMY

QGP photon rate: AMY

• HG photon rate: TGR for meson gas with viscous corrections

HG photon rate: TGR for meson gas with viscous corrections

• Generation of

Generation of pre pre-

• equilibrium flow

equilibrium flow: : using using free free-

• streaming model

streaming model to evolve the to evolve the partons partons right after the collisions to 0.6 fm/c right after the collisions to 0.6 fm/c + + Landau matching to switch to viscous Landau matching to switch to viscous h hydro ydro

• quick development of momentum anisotropy

quick development of momentum anisotropy with saturation near T with saturation near TC

C

Warning: Warning: results can be considered as results can be considered as upper limit upper limit for the pre for the pre-

• equilibrium flow effect!

equilibrium flow effect! ALICE (preliminary) ALICE (preliminary) Au+Au, Au+Au, 2760 2760 GeV GeV

• Pre

Pre-

• equilibrium flow:

equilibrium flow:

• small effect on photon spectra

small effect on photon spectra

• slight

slight increase of v increase of v2

2

• ‚

‚Initial Initial‘ ‘ flow: flow: rapid increase in bulk v rapid increase in bulk v2

2 in fireball model

in fireball model

van Hees, Gale, van Hees, Gale, Rapp, PRC84 (2011) 054906 Rapp, PRC84 (2011) 054906

SLIDE 14

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 14

Are thermal photons a QGP thermometer? Are thermal photons a QGP thermometer?

• Measured

Measured Teff > Teff > ‚ ‚true true‘ ‘ T T

• ,blue shift

,blue shift‘ ‘ due to the due to the radial flow radial flow! !

• nly
• nly ~1/3 at LHC

~1/3 at LHC and and ~1/4 at RHIC ~1/4 at RHIC of total photons come

• f total photons come

from hot QCD ( from hot QCD (T>250 MeV T>250 MeV) )

• (2+1)d viscous hydro VISH2+1

(2+1)d viscous hydro VISH2+1 (Ohio) (Ohio)

• C. Shen et al., PRC89 (2014) 044910; arXiv:1308.2440
• C. Shen et al., PRC89 (2014) 044910; arXiv:1308.2440
• Contour plots of differential photon yield

Contour plots of differential photon yield

• vs. time and temperature T and
• vs. time and temperature T and T

Teff

eff :

:

• T

Teff

eff=

= -

• 1/slope vs. local fluid cell temperature T

1/slope vs. local fluid cell temperature T

• Time evolution of the effective temperature

Time evolution of the effective temperature

• Exp. Data:
• Exp. Data:
• RHIC: T

RHIC: Teff

eff=221+19+19 MeV

=221+19+19 MeV

• LHC: T

LHC: Teff

eff=304+51 MeV

=304+51 MeV

T 1 1 T

eff

υ υ υ υ υ υ υ υ − − − − + + + + = = = =

SLIDE 15

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 15

What else?! What else?!

• Further

Further improvements of hydro models improvements of hydro models ? ?

• Bulk viscosity

Bulk viscosity

• Modeling of initial pre

Modeling of initial pre-

• equlibrium effects

equlibrium effects

• …

… From hydro to non From hydro to non-

• equilibrium

equilibrium microscopic transport models microscopic transport models : : use use PHSD as a PHSD as a ‚ ‚laboratory laboratory‘ ‘ for that for that

• Non

Non-

• equilibrium dynamics

equilibrium dynamics ? ?

• Missing strength related to

Missing strength related to hadronic stage hadronic stage? ?

SLIDE 16

• QGP phase

QGP phase is is described by the described by the D Dynamical ynamical Q Quasi uasiP Particle article M Model

• del (DQPM

DQPM)

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 16

• strongly interacting quasi

strongly interacting quasi-

• particles

particles

• massive quarks and gluons (g, q, q

massive quarks and gluons (g, q, qbar

bar)

) with sizeable collisional widths in with sizeable collisional widths in self self-

• generated

generated mean mean-

• field potential

field potential

P Parton arton-

• H

Hadron adron-

• S

String tring-

• D

Dynamics ( ynamics (PHSD PHSD) )

PHSD PHSD is a is a non non-

• equilibrium transport model

equilibrium transport model which provides the microscopic which provides the microscopic description of description of the full collision evolution the full collision evolution Basic ideas: Basic ideas:

• explicit

explicit phase transition phase transition from hadrons to partons from hadrons to partons

• lQCD EoS

lQCD EoS (cross over) (cross over) for the partonic phase for the partonic phase

• explicit

explicit parton parton-

• parton interactions

parton interactions -

• between quarks and gluons

between quarks and gluons

• dynamical

dynamical hadronization hadronization

• ff
• ff-
• shell

shell hadronic hadronic collision dynamics collision dynamics in the final reaction phase in the final reaction phase

• Transport theory

Transport theory: : generalized off generalized off-

• shell transport equations

shell transport equations based on the 1st order based on the 1st order gradient expansion of Kadanoff gradient expansion of Kadanoff-

• Baym equations

Baym equations ( (applicable for strongly interacting system applicable for strongly interacting system!) !)

• A. Peshier, W. Cassing, PRL 94 (2005) 172301;
• A. Peshier, W. Cassing, PRL 94 (2005) 172301;
• W. Cassing, NPA 791 (2007) 365: NPA 793 (2007)
• W. Cassing, NPA 791 (2007) 365: NPA 793 (2007)
• W. Cassing, E. B., PRC 78 (2008) 034919; NPA831 (2009) 215; W.
• W. Cassing, E. B., PRC 78 (2008) 034919; NPA831 (2009) 215; W. Cassing,

Cassing, E EPJ ST PJ ST 168 168 (2009) (2009) 3 3

( ( ( ( ) ) ) )

(T) ω 4 (T) M p ω (T) ω 4 ) T , ( ρ

2 i 2 2 2 i 2 2 i i

Γ Γ Γ Γ Γ Γ Γ Γ ω ω ω ω + + + + − − − − − − − − = = = =

• Spectral functions:

Spectral functions:

) g , q , q i ( = = = =

• DQPM

DQPM matches well matches well lattice QCD lattice QCD

SLIDE 17

100 200 300 400 0.00 0.01 0.02 0.03 0.04 0.05 0.06 100 200 300 400 0.000 0.002 0.004 0.006 0.008 0.010

NA57 NA49 HSD PHSD

Λ

Λ Λ Λ+Σ Σ Σ Σ

Nwound Nwound

Pb+Pb, 158 A GeV, mid-rapidity

_ _ Λ+Σ

Λ+Σ Λ+Σ Λ+Σ

dN/dy | y=0 / Nwound Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 september 2014 17

PHSD for HIC (highlights) PHSD for HIC (highlights)

• PHSD

PHSD provides a consistent provides a consistent description of HIC description of HIC

SLIDE 18

! ! sizeable contribution of hadronic

sizeable contribution of hadronic sources sources – – meson meson-

• meson (mm) and meson

meson (mm) and meson-

• Baryon

Baryon (mB) bremsstrahlung (mB) bremsstrahlung

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 18

PHSD: photon spectra at RHIC: QGP vs. HG ? PHSD: photon spectra at RHIC: QGP vs. HG ?

• Direct

Direct photon spectrum (min. bias) photon spectrum (min. bias)

Linnyk et al., PRC88 (2013) 034904; Linnyk et al., PRC88 (2013) 034904; PRC 89 (2014) 034908 PRC 89 (2014) 034908

PHSD: PHSD:

• QGP

QGP gives up to ~50% of direct photon gives up to ~50% of direct photon yield below 2 yield below 2 GeV GeV/c /c m+m m+m m+m+ m+m+γ, γ, m+B m+B m+B+ m+B+γ , γ , m= m=π,η,ρ,ω,Κ,Κ π,η,ρ,ω,Κ,Κ*, *,… … B= B=p p !!! !!! mm and mB bremsstrahlung channels mm and mB bremsstrahlung channels can not be subtracted experimentally can not be subtracted experimentally ! !

SLIDE 19

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 19

Photon p Photon pT

T spectra at RHIC for different centralities

spectra at RHIC for different centralities

PHSD predictions: PHSD predictions:

• O. Linnyk et al, Phys. Rev. C 89 (2014) 034908
• O. Linnyk et al, Phys. Rev. C 89 (2014) 034908

PHENIX data PHENIX data -

• arXiv:1405.3940

arXiv:1405.3940

from talk by S. Mizuno at QM from talk by S. Mizuno at QM‘ ‘2014 2014

• mm and mB bremsstrahlung is

mm and mB bremsstrahlung is dominant dominant at peripheral collisions at peripheral collisions

!!! Warning: !!! Warning: large uncertainties large uncertainties in the Bremsstrahlung channels in the present PHSD results ! in the Bremsstrahlung channels in the present PHSD results !

PHSD PHSD

• PHSD approximately reproduces

PHSD approximately reproduces the centrality dependence the centrality dependence

SLIDE 20

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 20

Bremsstrahlung Bremsstrahlung – – trivial trivial ‚ ‚background background‘ ‘? ?

• Uncertainties in the Bremsstrahlung channels

Uncertainties in the Bremsstrahlung channels in the present PHSD results : in the present PHSD results :

• C. Gale, J. Kapusta, Phys. Rev. C 35 (1987) 2107
• C. Gale, J. Kapusta, Phys. Rev. C 35 (1987) 2107
• Soft Photon Approximation (SPA):

Soft Photon Approximation (SPA): m m1

1+m

+m2

2

• m

m1

1+m

+m2

2+γ

+γ +γ +γ +γ +γ +γ +γ 2) no experimental constraint on 2) no experimental constraint on m+m and m+B differential elastic cross sections m+m and m+B differential elastic cross sections

• Bremsstrahlung:

Bremsstrahlung: seen at seen at SPS SPS -

• WA98

WA98

1) based on the 1) based on the Soft Soft-

• Photon

Photon-

• Approximation (SPA)

Approximation (SPA) (factorization = strong x EM) (factorization = strong x EM)

Firebal model: Liu, Rapp, Nucl. Phys. A 96 (2007) 101 Firebal model: Liu, Rapp, Nucl. Phys. A 96 (2007) 101

• effective chiral model for

effective chiral model for ππ ππ ππ ππ ππ ππ ππ ππ

• ππγ, πΚ

ππγ, πΚ ππγ, πΚ ππγ, πΚ ππγ, πΚ ππγ, πΚ ππγ, πΚ ππγ, πΚ

• πΚγ

πΚγ πΚγ πΚγ πΚγ πΚγ πΚγ πΚγ bremsstrahlung bremsstrahlung gives larger contribution gives larger contribution than SPA than SPA

HSD: E. B., Kiselev, Sharkov, PR C78 (2008) 034905 HSD: E. B., Kiselev, Sharkov, PR C78 (2008) 034905

using SPA using SPA

• mm and mB Bremsstrahlung seams to be

mm and mB Bremsstrahlung seams to be an important source of soft photons! an important source of soft photons! More work has to be done to have it under More work has to be done to have it under control! control!

SLIDE 21

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 21

Centrality dependence of the Centrality dependence of the ‚ ‚thermal thermal‘ ‘ photon yield photon yield

• PHSD:

PHSD: scaling of the scaling of the thermal thermal photon yield with photon yield with N Npart

partα

α α α α α α α with

with α α α α α α α α~1.5 ~1.5

• similar results from

similar results from viscous hydro: viscous hydro: (2+1)d (2+1)d VISH2+1: VISH2+1: α α α α α α α α(HG) ~1.46, (HG) ~1.46, α α α α α α α α(QGP) ~2, (QGP) ~2, α α α α α α α α(total) ~1.7 (total) ~1.7

• O. Linnyk et al, Phys. Rev. C 89 (2014) 034908
• O. Linnyk et al, Phys. Rev. C 89 (2014) 034908

PHSD predictions: PHSD predictions:

• Hadronic channels

Hadronic channels scale as ~ N scale as ~ Npart

part1.5 1.5

• Partonic channels

Partonic channels scale as scale as ~N ~Npart

part1.75 1.75

( (‘ ‘Thermal Thermal’ ’ photon yield photon yield = direct photons = direct photons -

• pQCD)

pQCD) PHENIX PHENIX (arXiv:1405.3940): (arXiv:1405.3940): scaling of scaling of thermal thermal photon yield vs centrality: photon yield vs centrality: dN/dy ~ dN/dy ~ N Npart

partα

α α α α α α α with

with α α α α α α α α~1.48 ~1.48+ +0.08 0.08

• What do we learn?

What do we learn? Indications for a dominant Indications for a dominant hadronic origin of thermal photon production?! hadronic origin of thermal photon production?!

SLIDE 22

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 22

1) 1) v v2

2(

(γ γ γ γ γ γ γ γincl

incl) =

) = v v2

2(

(π π π π π π π π0

0 )

) -

• inclusive photons

inclusive photons mainly come from mainly come from π π π π π π π π0

0 decays

decays

• model without QGP (HSD) underestimates

model without QGP (HSD) underestimates v v2

2 of hadrons

• f hadrons and inclusive photons by a factor of 2

and inclusive photons by a factor of 2 wheras the model with QGP (PHSD) is consistent with exp. data wheras the model with QGP (PHSD) is consistent with exp. data

0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.1 0.2 0.3 , PHENIX v2

dir= Σ

Σ Σ Σi v2

i Ni(γ

γ γ γ)/Ntot(γ γ γ γ)

PHSD

pT [GeV/c]

direct photon v2 in PHSD Au+Au, sNN

1/2=200 GeV, MB, |y|<0.35

v2

Are the direct photons a barometer of the QGP? Are the direct photons a barometer of the QGP?

Linnyk et al., PRC88 (2013) 034904; Linnyk et al., PRC88 (2013) 034904; PRC 89 (2014) 034908 PRC 89 (2014) 034908

2) 2) v v2

2(

(γ γ γ γ γ γ γ γdir

dir)

) of

• f direct photons

direct photons in PHSD underestimates the PHENIX data : in PHSD underestimates the PHENIX data : v v2

2(

(γ γ γ γ γ γ γ γQGP

QGP) is very small

) is very small, but QGP contribution is up to 50% of total yield , but QGP contribution is up to 50% of total yield

• lowering flow

lowering flow

• Do we see the QGP

Do we see the QGP pressure pressure in v in v2

2(

(γ γ γ γ γ γ γ γ) if the photon production ) if the photon production is is dominated by hadronic sources? dominated by hadronic sources? HSD(no QGP) HSD(no QGP)

• The

The QGP causes the strong elliptic QGP causes the strong elliptic flow of photons indirectly, flow of photons indirectly, by enhancing the v by enhancing the v2

2

• f final hadrons due to the partonic interactions
• f final hadrons due to the partonic interactions
• PHSD:

PHSD: v v2

2(

(γ γ γ γ γ γ γ γdir

dir) comes from

) comes from mm and mB bremsstrahlung ?! mm and mB bremsstrahlung ?!

SLIDE 23

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 23

Photons from PHSD at LHC Photons from PHSD at LHC

• Is the considerable

Is the considerable elliptic flow elliptic flow of direct photons at

• f direct photons at

the LHC also of the LHC also of hadronic origin hadronic origin as for RHIC?! as for RHIC?!

• The photon elliptic flow at LHC is lower than at RHIC

The photon elliptic flow at LHC is lower than at RHIC due to due to a larger relative QGP contribution / longer QGP a larger relative QGP contribution / longer QGP phase. phase.

PHSD: PHSD: v v2

2 of inclusive photons

• f inclusive photons

P r e l i m i n a r y P r e l i m i n a r y P r e l i m i n a r y P r e l i m i n a r y

PHSD PHSD-

• preliminary: Olena Linnyk

preliminary: Olena Linnyk

PHSD: PHSD: direct photons direct photons

• LHC (similar to RHIC):

LHC (similar to RHIC): hadronic photons d hadronic photons dominate spectra and v

• minate spectra and v2

2

SLIDE 24

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 24

Towards the solution of the Towards the solution of the v v2

2 puzzle

puzzle

? ?

• Is

Is hadronic bremsstrahlung hadronic bremsstrahlung a a ‚ ‚solution solution‘ ‘? ?

• Pseudo

Pseudo-

• Critical Enhancement of thermal photons near T

Critical Enhancement of thermal photons near TC

C ?

?

(H. van Hees, M. He, R. Rapp, arXiv:1404.2846) (H. van Hees, M. He, R. Rapp, arXiv:1404.2846)

• cf. talk by R. Rapp
• cf. talk by R. Rapp -
• „

„Electromagnetic probes: 2 Electromagnetic probes: 2-

• 2

2“ “ (Monday) (Monday)

Other scenarios: Other scenarios:

• Early

Early-

• time magnetic field effects

time magnetic field effects ? ?

( (Basar Basar, , Kharzeev Kharzeev, , Skokov Skokov, PRL , PRL109 109 (2012) (2012) 202303 202303; ; Basar Basar, , Kharzeev Kharzeev, , Shuryak Shuryak, , arXiv arXiv:1402.2286) :1402.2286) „ „ … … a novel photon production mechanism stemming from the a novel photon production mechanism stemming from the conformal anomaly of conformal anomaly of QCD QCD-

• QED and the existence of strong (electro)magnetic fields

QED and the existence of strong (electro)magnetic fields in heavy ion collisions. in heavy ion collisions.“ “

• Exp. checks
• Exp. checks: v

: v3

3 ,

, centrality dependence of photon yield (PHENIX: arXiv:1405.3940) centrality dependence of photon yield (PHENIX: arXiv:1405.3940)

• Glasma effects

Glasma effects ? ?

(L. (L. McLerran McLerran, B. Schenke, arXiv: 1403.7462 , B. Schenke, arXiv: 1403.7462) ) „ „ … … Photon distributions from the Glasma are Photon distributions from the Glasma are steeper steeper than those computed in the than those computed in the Thermalized Quark Gluon Plasma (TQGP). Both the Thermalized Quark Gluon Plasma (TQGP). Both the delayed equilibration of the Glasma delayed equilibration of the Glasma and and a possible anisotropy in the pressure lead to a slower expansion a possible anisotropy in the pressure lead to a slower expansion and mean times of photon and mean times of photon emission of fixed energy are increased. emission of fixed energy are increased.“ “

• non

non-

• perturbative effects?

perturbative effects?

semi semi-

• QGP

QGP -

• cf. talk by S. Lin
• cf. talk by S. Lin -
• „

„Electromagnetic probes: 2 Electromagnetic probes: 2-

• 2

2“ “ (Monday) (Monday)

• ???

???

SLIDE 25

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 25

… … shining in the darkness shining in the darkness

• Can thermal QGP accelerate photons enough?!

Can thermal QGP accelerate photons enough?!

• The role of

The role of hadronic sources (like bremsstrahlung) were underestimated? hadronic sources (like bremsstrahlung) were underestimated?

• The

The importance of initial phases importance of initial phases of the reaction:

• f the reaction:

Large photon v Large photon v2

2 requires the development of pre

requires the development of pre-

• equilibrium / initial flow ?!

equilibrium / initial flow ?!

• New sources

New sources of photon emission? Why not seen in dileptons?!

• f photon emission? Why not seen in dileptons?!
• The photons provide a

The photons provide a critical test for the theoretical models critical test for the theoretical models: : models constructed to reproduce the models constructed to reproduce the ‚ ‚hadronic world hadronic world‘ ‘ fail to explain the photon fail to explain the photon experimental data! experimental data!

• Additional impuls for the development of

Additional impuls for the development of dynamical models dynamical models: : e.g. from ideal to ebe viscous hydro, EoS, realistic non e.g. from ideal to ebe viscous hydro, EoS, realistic non-

• equilibrium dynamics

equilibrium dynamics … …

Some Some messages messages from the from the ‘ ‘photon adventure photon adventure’ ’: :

Photons Photons – – one of the most sensitive probes for the dynamics of HIC!

• ne of the most sensitive probes for the dynamics of HIC!

SLIDE 26

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 26

Dileptons: from SPS to LHC Dileptons: from SPS to LHC

SLIDE 27

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 27

Dilepton sources Dilepton sources

• from the QGP

from the QGP via partonic (q,qbar, g) interactions: via partonic (q,qbar, g) interactions:

• from hadronic sources:

from hadronic sources:

• direct decay

direct decay of vector

• f vector

mesons ( mesons (ρ,ω,φ, ρ,ω,φ, ρ,ω,φ, ρ,ω,φ, ρ,ω,φ, ρ,ω,φ, ρ,ω,φ, ρ,ω,φ,J J/Ψ,Ψ /Ψ,Ψ /Ψ,Ψ /Ψ,Ψ /Ψ,Ψ /Ψ,Ψ /Ψ,Ψ /Ψ,Ψ‘ ‘) )

• Dalitz decay

Dalitz decay of mesons

• f mesons

and baryons and baryons ( (π π π π π π π π0

0,

,η η η η η η η η, , ∆ ∆ ∆ ∆ ∆ ∆ ∆ ∆, ,… …) )

• correlated D+Dbar pairs

correlated D+Dbar pairs

• radiation from

radiation from multi multi-

• meson reactions

meson reactions ( (π π π π π π π π+ +π π π π π π π π, , π π π π π π π π+ +ρ ρ ρ ρ ρ ρ ρ ρ, , π π π π π π π π+ +ω ω ω ω ω ω ω ω, , ρ ρ ρ ρ ρ ρ ρ ρ+ +ρ ρ ρ ρ ρ ρ ρ ρ , , π π π π π π π π+a +a1

1)

) -

• ‚

‚4 4π π π π π π π π‘ ‘

γ γ γ γ γ γ γ γ* * g g γ γ γ γ γ γ γ γ* * γ γ γ γ γ γ γ γ* * q q l+ l-

• γ

γ γ γ γ γ γ γ*

*

q q q q q q q q q q q q g g g g q q

c c D K −

− − − + + + +

• ν

ν ν ν

• D

K +

+ + + − − − −

• ν

ν ν ν

• c

c D K −

− − − + + + +

• ν

ν ν ν

• D

K +

+ + + − − − −

• ν

ν ν ν

• iessen

Joachim Stroth

+qq +qq

Plot from A. Drees Plot from A. Drees

‚ ‚thermal QGP thermal QGP‘ ‘

SLIDE 28

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna) 3 September 2014 28

Physics with dilepton Physics with dilepton

iessen Joachim Stroth

Low mass dileptons Low mass dileptons

• probe of

probe of hadronic hadronic in in-

• medium effects

medium effects (late time emission) (late time emission) Intermediate mass Intermediate mass dileptons dileptons – – probe of probe of ‚ ‚thermal QGP thermal QGP‘ ‘ High High-

• mass dileptons

mass dileptons – – probe of probe of pQGP and pQGP and hard probes hard probes (early time emission) (early time emission)

+qq +qq

Advantage of dileptons: Advantage of dileptons: additional additional „ „degree of freedom degree of freedom“ “ ( (M M) allows to ) allows to disentangle various sources disentangle various sources

SLIDE 29

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 29

Lessons from SPS: NA60 Lessons from SPS: NA60

PHSD: PHSD: Linnyk et al, PRC 84 (2011) Linnyk et al, PRC 84 (2011) 054917 054917

• Dilepton invariant mass spectra:

Dilepton invariant mass spectra:

Fireball model Fireball model – – Renk/Ruppert Renk/Ruppert Fireball model Fireball model – – Rapp/vanHees Rapp/vanHees Ideal hydro model Ideal hydro model – – Dusling/Zahed Dusling/Zahed

Hybrid Hybrid-

• UrQMD:

UrQMD: Santini et al., Santini et al., PRC84 (2011) 014901 PRC84 (2011) 014901

Message from SPS: (based on NA60 and CERES data) Message from SPS: (based on NA60 and CERES data) 1) 1) Low mass spectra Low mass spectra -

• evidence for the

evidence for the in in-

• medium broadening of

medium broadening of ρ ρ ρ ρ ρ ρ ρ ρ-

• mesons

mesons 2) 2) Intermediate mass Intermediate mass spectra above 1 spectra above 1 GeV GeV -

• dominated by

dominated by partonic radiation partonic radiation 3) 3) The rise and fall of The rise and fall of T

Teff

eff –

– evidence for the thermal evidence for the thermal QGP radiation QGP radiation 4) 4) Isotropic angular distribution Isotropic angular distribution – – indication for a indication for a thermal origin of dimuons thermal origin of dimuons

• Inverse slope parameter T

Inverse slope parameter Teff

eff:

:

spectrum from QGP is softer than from hadronic phase since the Q spectrum from QGP is softer than from hadronic phase since the QGP GP emission occurs dominantly before the collective radial flow has emission occurs dominantly before the collective radial flow has developed developed

NA60: NA60: Eur. Phys. J. C 59 (2009)

• Eur. Phys. J. C 59 (2009) 607

607

QGP QGP

PRL 102 (2009) 222301 PRL 102 (2009) 222301

SLIDE 30

co coc cktail ktail

HSD HSD

Ideal hydro Ideal hydro Dusling/Zahed Dusling/Zahed Fireball model Fireball model Rapp/vanHees Rapp/vanHees

co coc cktail ktail

HSD HSD

Ideal hydro Ideal hydro Dusling/Zahed Dusling/Zahed Fireball model Fireball model Rapp/vanHees Rapp/vanHees

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 30

Dileptons at RHIC: PHENIX Dileptons at RHIC: PHENIX

Message: Message:

• Models

Models provide a provide a good description of pp data good description of pp data and and peripheral peripheral Au+Au Au+Au data, however, data, however, fail in describing the excess for central fail in describing the excess for central collisions collisions even with even with in in-

• medium scenarios

medium scenarios for the vector meson for the vector meson spectral function spectral function

• The

The ‘ ‘missing source missing source’ ’(?) (?) is located at is located at low low p pT

T

• Intermediate mass spectra

Intermediate mass spectra – – dominant QGP contribution dominant QGP contribution

PHENIX: PHENIX: PRC81 PRC81 (2010) (2010) 034911 034911 Linnyk et al., PRC 85 (2012) 024910 Linnyk et al., PRC 85 (2012) 024910

SLIDE 31

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 31

Dileptons at RHIC: STAR data vs model predictions Dileptons at RHIC: STAR data vs model predictions

Centrality dependence of dilepton yield Centrality dependence of dilepton yield (Talk by P. Huck at QM (Talk by P. Huck at QM‘ ‘2 2014 014) )

Message: Message: STAR data

STAR data are described by models within a are described by models within a collisional broadening collisional broadening scenario scenario for the vector meson spectral function + for the vector meson spectral function + QGP QGP Excess in low mass region, min. bias Excess in low mass region, min. bias Models: Models:

• Fireball model

Fireball model – – R. Rapp

• R. Rapp
• PHSD

PHSD Low masses: Low masses: collisional broadening of collisional broadening of ρ ρ ρ ρ ρ ρ ρ ρ Intermediate masses: Intermediate masses: QGP dominant QGP dominant

SLIDE 32

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 32

Dileptons from RHIC BES: STAR Dileptons from RHIC BES: STAR

Message: Message:

• BES

BES-

• STAR

STAR data

data show a show a constant low mass constant low mass excess excess (scaled with N( (scaled with N(π π π π π π π π0

0)) within the measured

)) within the measured energy range energy range

• PHSD model:

PHSD model: excess increasing with excess increasing with decreasing energy decreasing energy due to a longer due to a longer ρ ρ ρ ρ ρ ρ ρ ρ-

• propagation

propagation in the high baryon density phase in the high baryon density phase

• Good perspectives for future experiments

Good perspectives for future experiments – – CBM(FAIR) / MPD(NICA) CBM(FAIR) / MPD(NICA) (Talk by Nu Xu at QM (Talk by Nu Xu at QM‘ ‘2 2014 014) )

(Talk by Nu Xi at 23d CBM Meeting (Talk by Nu Xi at 23d CBM Meeting‘ ‘14 14) )

SLIDE 33

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 33

Dileptons at LHC Dileptons at LHC

Message: Message:

• low masses

low masses -

• hadronic sources:

hadronic sources: in in-

• medium effects for

medium effects for ρ ρ ρ ρ ρ ρ ρ ρ mesons are small mesons are small

• intermediate masses:

intermediate masses: QGP + D/ QGP + D/Dbar Dbar

• charm

charm ‘ ‘background background’ ’ is smaller than thermal QGP yield is smaller than thermal QGP yield

• QGP(

QGP(qbar qbar-

• q)

q) dominates at M>1.2 dominates at M>1.2 GeV GeV

• clean signal of QGP at LHC!

clean signal of QGP at LHC!

• O. Linnyk, W. Cassing, J. Manninen, E.B., P.B.
• O. Linnyk, W. Cassing, J. Manninen, E.B., P.B.

Gossiaux, J. Aichelin, T. Song, C. Gossiaux, J. Aichelin, T. Song, C.-

• M. Ko,
• M. Ko,

Phys.Rev. C87 (2013) 014905 Phys.Rev. C87 (2013) 014905; arXiv:1208.1279 ; arXiv:1208.1279

QGP QGP

SLIDE 34

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 34

Perspectives with dileptons: v Perspectives with dileptons: vn

n

M= M=m mρ

ρ ρ ρ ρ ρ ρ ρ

(3+1)d MUSIC: (3+1)d MUSIC: Au+Au, RHIC, 10% central Au+Au, RHIC, 10% central

Vujanovic, Young, Schenke, Rapp, Jeon, Gale Vujanovic, Young, Schenke, Rapp, Jeon, Gale, PRC 89 (2014) 034904 , PRC 89 (2014) 034904 Talk by Talk by Vujanovic Vujanovic, QM , QM‘ ‘2014 2014

M=1.5 M=1.5 GeV GeV v v2

2 (similar for v

(similar for v3

3 ):

):

• sensitive to the

sensitive to the EoS EoS and and η η η η η η η η/s /s

• sensitive to the sources

sensitive to the sources Dileptons: advantages compared to photons Dileptons: advantages compared to photons – – extra degree of freedom M allows to disentangle extra degree of freedom M allows to disentangle the sources! the sources!

SLIDE 35

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 35

Messages from dilepton data Messages from dilepton data

• Low dilepton masses:

Low dilepton masses:

• Dilepton spectra

Dilepton spectra show show sizeable changes due to the in sizeable changes due to the in-

• medium effects

medium effects – – modification of the properties of vector mesons modification of the properties of vector mesons (as collisional (as collisional broadening) broadening) -

• which are observed experimentally

which are observed experimentally

• In

In-

• medium effects

medium effects can be observed at can be observed at all energies from SIS to LHC all energies from SIS to LHC

• Intermediate dilepton masses:

Intermediate dilepton masses:

• T

The he QGP QGP ( (qbar qbar-

• q) dominates for M>1.2

q) dominates for M>1.2 GeV GeV

• Fraction of QGP

Fraction of QGP grows grows with increasing energy; with increasing energy; at the LHC it is dominant at the LHC it is dominant

iessen Joachim Stroth

+qq +qq

Outlook: Outlook: * * experimental experimental energy scan energy scan * e * experimental measurements of dilepton xperimental measurements of dilepton’ ’s s higher flow harmonics higher flow harmonics v vn

n

SLIDE 36

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna) 3 september 2014 36

FIAS & Frankfurt University FIAS & Frankfurt University Elena Bratkovskaya Elena Bratkovskaya Rudy Marty Rudy Marty Hamza Berrehrah Hamza Berrehrah Daniel Cabrera Daniel Cabrera Taesoo Song Taesoo Song Andrej Ilner Andrej Ilner Giessen University Giessen University Wolfgang Cassing Wolfgang Cassing Olena Linnyk Olena Linnyk Volodya Konchakovski Volodya Konchakovski Thorsten Steinert Thorsten Steinert Alessia Palmese Alessia Palmese Eduard Seifert Eduard Seifert

External Collaborations External Collaborations

SUBATECH, Nantes University: SUBATECH, Nantes University: J Jö örg Aichelin rg Aichelin Christoph Hartnack Christoph Hartnack Pol Pol-

• Bernard Gossiaux

Bernard Gossiaux Vitalii Ozvenchuk Vitalii Ozvenchuk Texas A&M University: Texas A&M University: Che Che-

• Ming Ko

Ming Ko JINR, Dubna: JINR, Dubna: Viacheslav Toneev Viacheslav Toneev Vadim Voronyuk Vadim Voronyuk BITP, Kiev University: BITP, Kiev University: Mark Gorenstein Mark Gorenstein Barcelona University: Barcelona University: Laura Tolos Laura Tolos Angel Ramos Angel Ramos

PHSD group PHSD group

SLIDE 37

Elena Bratkovskaya (Uni. Frankfurt) JINR (Dubna), 3 September 2014 37

Thank you! Thank you!