resonances from phsd · 2012. 3. 13. · 10-1 10 0 10 1 10 2 10 3 10 4 10-6 10-4 10-2 10 0 10 2 10...

Resonances from PHSD

EElenalena BratkovskayaBratkovskaya

Institut fInstitut füür Theoretische Physikr Theoretische Physik & FIAS, Uni. Frankfurt& FIAS, Uni. Frankfurt

WWorkshop on "Hadronic resonance production in elementaryorkshop on "Hadronic resonance production in elementary

and heavyand heavy--ion collisions ion collisions

AustinAustin, USA, , USA, 55--7 7 March 2012 March 2012

The holy grail:The holy grail:

•• Study of the Study of the phase phase

transitiontransition from from

hadronic to partonic hadronic to partonic

matter matter ––

QuarkQuark--GluonGluon--PlasmaPlasma

•• Search for the Search for the critical pointcritical point

•• Study of the Study of the inin--mediummedium properties of hadrons at high baryon density properties of hadrons at high baryon density

and temperatureand temperature

•• Study of the partonic medium beyond the phase boundaryStudy of the partonic medium beyond the phase boundary

The phase diagram of QCDThe phase diagram of QCD

2

Study of inStudy of in--medium effects within medium effects within

transport approachestransport approaches

InIn--medium models:medium models:

�� chiral perturbation theory chiral perturbation theory

�� chiral SU(3) model chiral SU(3) model

�� coupledcoupled--channel Gchannel G--matrix approachmatrix approach

�� chiral coupledchiral coupled--channel effective field channel effective field

theory theory

predict predict changes of the particle propertieschanges of the particle properties

in the hot and dense medium, e.g. in the hot and dense medium, e.g.

broadening of the spectral function broadening of the spectral function

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B,T) (GeV

-2)

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M (GeV/c2)

ρρρρB=3ρρρρ

0

q (

GeV

/c)

R. Rapp:R. Rapp: ρρρρρρρρ meson spectral functionmeson spectral function

•• Accounting forAccounting for inin--medium effects medium effects with with

mediummedium--dependent spectral functionsdependent spectral functions requires requires

offoff--shell transport models ! shell transport models !

From KadanoffFrom Kadanoff--Baym equations to transport equations Baym equations to transport equations

After the first order gradient expansion of the Wigner transformAfter the first order gradient expansion of the Wigner transformed ed KadanoffKadanoff--BaymBaym

equations equations and separation into the real and imaginary parts one gets:and separation into the real and imaginary parts one gets:

drift termdrift term Vlasov termVlasov term collision term =collision term = ‚‚lossloss‘‘ termterm -- ‚‚gaingain‘‘ termtermbackflow termbackflow term

Generalized transport equations:Generalized transport equations:

Backflow termBackflow term incorporates the incorporates the offoff--shellshell behavior in the particle propagationbehavior in the particle propagation

!! vanishes in the quasiparticle limit vanishes in the quasiparticle limit AAXPXP = 2 = 2 ππππππππ δδδδδδδδ(p(p22--MM22) )

��‚‚onon--shellshell‘‘ transport models (VUU, BUU, QMD, IQMD, UrQMD etc.)transport models (VUU, BUU, QMD, IQMD, UrQMD etc.)

The imaginary part of the retarded propagator is given by the noThe imaginary part of the retarded propagator is given by the normalizedrmalized spectral function:spectral function:

For bosons in first order gradient expansion:For bosons in first order gradient expansion:

ΓΓΓΓΓΓΓΓXPXP –– width of spectral functionwidth of spectral function = = reaction ratereaction rate of of

particle (at phaseparticle (at phase--space position XP)space position XP)

44--dimentional generalizaton of the Poissondimentional generalizaton of the Poisson--bracket:bracket:

Greens function SGreens function S<< characterizes the characterizes the number of particlesnumber of particles (N) and their properties (N) and their properties

(A (A –– spectral functionspectral function ): ): iiSS<<XPXP=A=AXPXPNNXPXP

General testparticle offGeneral testparticle off--shell equations of motionshell equations of motion

Employ Employ testparticle Ansatztestparticle Ansatz for the real valued quantity for the real valued quantity ii SS<<XP XP --

insert in generalized transport equationsinsert in generalized transport equations and determine equations of motion !and determine equations of motion !

General testparticle offGeneral testparticle off--shell equations of motion:shell equations of motion:

with

W. Cassing , S. Juchem, NPA 665 (2000) 377; 672 (2000) 417; 677 W. Cassing , S. Juchem, NPA 665 (2000) 377; 672 (2000) 417; 677 (2000) 445(2000) 445

OffOff--shell vs. onshell vs. on--shell transport dynamicsshell transport dynamics

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C+C, 2.0 A GeV, b=1 fm

dropp. mass + coll. broad.

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/dM

[a.u

.]

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time [fm/c]

ρρρρ-meson

off-shell ρρρρ-meson

on-shell

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/dM

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.]

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on-shell

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/dM

[a.u

.]

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time [fm/c]

ωωωω-meson

off-shell

dN

/dM

[a.u

.]

M [GeV/c2 ]

time [fm/c]

The offThe off--shell spectral function becomes onshell spectral function becomes on--shell in the vacuum dynamically shell in the vacuum dynamically

by propagation through the medium!by propagation through the medium!

Time evolution of the mass distribution of Time evolution of the mass distribution of ρ ρ ρ ρ ρ ρ ρ ρ andand ω ω ω ω ω ω ω ω mesons for central C+C mesons for central C+C

collisions (b=1 fm) at 2 A GeV for collisions (b=1 fm) at 2 A GeV for dropping mass + collisional broadening scenariodropping mass + collisional broadening scenario

E.L.B. &W. Cassing, NPA 807 (2008) 214E.L.B. &W. Cassing, NPA 807 (2008) 214

OnOn--shell model:shell model:

low mass low mass ρ ρ ρ ρ ρ ρ ρ ρ andand ω ω ω ω ω ω ω ω mesons live forever mesons live forever

and shine dileptons!and shine dileptons!

HSDHSD –– HHadronadron--SStringtring--DDynamics transport approach: ynamics transport approach:

•• for each particle species for each particle species ii ((i i = = NN, , RR, , YY, , ππππππππ, , ρρρρρρρρ, K, , K, ……) the phase) the phase--space density fspace density fi i followsfollows

the the generalized transport equations generalized transport equations

with with collision termscollision terms IIcoll coll describing:describing:

�� elastic and inelastic elastic and inelastic hadronic reactions: hadronic reactions:

baryonbaryon--baryon, mesonbaryon, meson--baryon, mesonbaryon, meson--mesonmeson

�� formation and decay of formation and decay of

baryonic and mesonicbaryonic and mesonic resonancesresonances

and and stringsstrings -- excited color singlet states excited color singlet states (qq (qq -- q)q) or or (q (q –– qbar) qbar) --

(for inclusive particle production: BB (for inclusive particle production: BB −−−−−−−−>>>>>>>> X , mB X , mB −−−−−−−−>>>>>>>>X, X =many particles)X, X =many particles)

•• implementation of implementation of detailed balance detailed balance on the level of 1on the level of 1<<<<<<<<−−−−−−−−>>>>>>>>22

and 2and 2<<<<<<<<−−−−−−−−>>>>>>>>2 reactions (+ 2 reactions (+ 22<<<<<<<<−−−−−−−−>>>>>>>>n multin multi--particle reactions in HSD !particle reactions in HSD !))

•• offoff--shell dynamicsshell dynamics for shortfor short--lived states lived states

The baseline concepts of HSDThe baseline concepts of HSD

BB BB <<<<<<<<−−−−−−−−> > > > > > > > BB´́BB´́, BB , BB <<<<<<<<−−−−−−−−> > > > > > > > BB´́BB´́mm

mB mB <<<<<<<<−−−−−−−−> > > > > > > > mm´́BB´́, mB , mB <<<<<<<<−−−−−−−−> > > > > > > > BB´́

Baryons: Baryons:

B=(p, n, B=(p, n, ∆(1232)∆(1232)∆(1232)∆(1232)∆(1232)∆(1232)∆(1232)∆(1232), ,

N(1440), N(1535), ...)N(1440), N(1535), ...)

Mesons: Mesons:

m=(m=(ππππππππ, , ηηηηηηηη, , ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)

HSD is an open code:HSD is an open code: http://www.th.physik.uni-frankfurt.de/~brat/hsd.html

(Collision term) Description of elementary reactions in HSD(Collision term) Description of elementary reactions in HSD

Low energy collisions:Low energy collisions:

•• binary 2binary 2<<<<<<<<−−−−−−−−>2>2>2>2>2>2>2>2 andand

22<<<<<<<<−−−−−−−−>>>>>>>>3 reactions 3 reactions

•• formation and formation and

decay of baryonic and decay of baryonic and

mesonic resonancesmesonic resonances

BB BB <<<<<<<<−−−−−−−−> > > > > > > > BB´́BB´́

BB BB <<<<<<<<−−−−−−−−> > > > > > > > BB´́BB´́mm

mB mB <<<<<<<<−−−−−−−−> > > > > > > > mm´́BB´́

mB mB <<<<<<<<−−−−−−−−> > > > > > > > BB´́

mm mm <<<<<<<<−−−−−−−−> > > > > > > > mm´́mm´́

mm mm <<<<<<<<−−−−−−−−> > > > > > > > mm´́

. . .. . .

Baryons: Baryons:

B=(p, n, B=(p, n, ∆(1232)∆(1232)∆(1232)∆(1232)∆(1232)∆(1232)∆(1232)∆(1232), ,

N(1440), N(1535), ...)N(1440), N(1535), ...)

Mesons: Mesons:

m=(m=(ππππππππ, , ηηηηηηηη, , ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)ρ, ω, φ, ...)

ππππππππ++pp

pppp

High energy High energy

collisions:collisions:

(above s(above s1/21/2~2.5 GeV)~2.5 GeV)

Inclusive particle Inclusive particle

production:production:

BB BB −−−−−−−−>>>>>>>> X , mB X , mB −−−−−−−−>>>>>>>>XX

X =many particlesX =many particles

described by described by

strings strings (= excited color (= excited color

singlet states singlet states qq--qqqq, ,

qq--qbarqbar)) formation and formation and

decaydecay

•• very good description of particle production invery good description of particle production in pp, pA, AA reactionspp, pA, AA reactions

•• unique description of nuclear dynamicsunique description of nuclear dynamics fromfrom low low (~100 MeV)(~100 MeV) to to

ultrarelativistic ultrarelativistic (>20 TeV) energies(>20 TeV) energies

HSD HSD –– a microscopic model for heavya microscopic model for heavy--ion reactionsion reactions

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φφφφ

K−−−−

K+

ηηηη

ππππ+

Mu

ltip

lici

ty

Au+Au (central)

Energy [A GeV]

HSD predictions from 1999; data from the new milleniumHSD predictions from 1999; data from the new millenium

HadronHadron--string string transport models transport models

(HSD, UrQMD) versus observables (HSD, UrQMD) versus observables

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+>

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Au+Au / Pb+Pb -> K++X

T [

GeV

]

HSD

HSD with Cronin eff.

UrQMD

‚‚hornhorn‘‘

in Kin K++//ππππππππ++

‚‚stepstep‘‘

in slope Tin slope T

Exp. data are not reproduced in terms of the hadronExp. data are not reproduced in terms of the hadron--string picture string picture

=> evidence for=> evidence for nonhadronic degrees of freedomnonhadronic degrees of freedom

•• Strangeness signals of QGPStrangeness signals of QGP

PRC 69 (2004) 032302PRC 69 (2004) 03230210

From hadrons to partonsFrom hadrons to partons

In order to study the In order to study the phase transitionphase transition from from

hadronic to partonic matter hadronic to partonic matter –– QuarkQuark--GluonGluon--PlasmaPlasma ––

we we need need a a consistent nonconsistent non--equilibrium (transport) model withequilibrium (transport) model with

��explicit explicit partonparton--parton interactionsparton interactions (i.e. between quarks and gluons) (i.e. between quarks and gluons)

beyond strings!beyond strings!

��explicit explicit phase transitionphase transition from hadronic to partonic degrees of freedomfrom hadronic to partonic degrees of freedom

��lQCD EoS lQCD EoS for partonic phasefor partonic phase

PPartonarton--HHadronadron--SStringtring--DDynamics (ynamics (PHSDPHSD))

QGP phase QGP phase described bydescribed by

DDynamical ynamical QQuasiuasiPParticle article MModel odel (DQPMDQPM)

Transport theoryTransport theory: off: off--shell Kadanoffshell Kadanoff--Baym equations for the Baym equations for the

GreenGreen--functions Sfunctions S<<hh(x,p) in phase(x,p) in phase--space representation for thespace representation for the

partonic partonic andand hadronic phasehadronic phase

A. A. Peshier, W. Cassing, PRL 94 (2005) 172301;Peshier, W. Cassing, PRL 94 (2005) 172301;

Cassing, NPA 791 (2007) 365: NPA 793 (2007) Cassing, NPA 791 (2007) 365: NPA 793 (2007)

W. Cassing, E. Bratkovskaya, PRC 78 (2008) 034919;W. Cassing, E. Bratkovskaya, PRC 78 (2008) 034919;

NPA831 (2009) 215; NPA831 (2009) 215;

W. Cassing, W. Cassing, EEPJ ST PJ ST 168168 (2009) (2009) 33

The Dynamical QuasiParticle Model (DQPM)The Dynamical QuasiParticle Model (DQPM)

Peshier, Cassing, PRL 94 (2005) 172301; Cassing, NPA 791 (2Peshier, Cassing, PRL 94 (2005) 172301; Cassing, NPA 791 (2007) 365: NPA 793 (2007) 007) 365: NPA 793 (2007)

�� Quasiparticle properties:Quasiparticle properties:

�� large width and mass for gluons and quarks large width and mass for gluons and quarks

••DQPMDQPM matches well matches well lattice QCDlattice QCD

••DQPMDQPM provides provides meanmean--fields (1PI) for gluons and quarksfields (1PI) for gluons and quarks

as well as as well as effective 2effective 2--body interactions (2PI)body interactions (2PI)

••DQPMDQPM gives gives transition ratestransition rates for the formation of hadrons for the formation of hadrons �� PHSDPHSD

Basic idea:Basic idea: Interacting quasiparticles Interacting quasiparticles

-- massive quarks and gluonsmassive quarks and gluons (g, q, q(g, q, qbarbar)) with with spectral functions :spectral functions :

�� fit to lattice (lQCD) resultsfit to lattice (lQCD) results (e.g. entropy density)(e.g. entropy density)

PHSD PHSD -- basic conceptbasic concept

Initial A+A collisions Initial A+A collisions –– HSD: HSD: string formation and decay to prestring formation and decay to pre--hadronshadrons

Fragmentation of preFragmentation of pre--hadrons into quarks:hadrons into quarks: using the quark spectral

functions from the Dynamical QuasiParticle ModelDynamical QuasiParticle Model ((DQPM) -

approximation to QCD

Partonic phase: Partonic phase: quarks and gluons (= quarks and gluons (= ‚‚dynamical quasiparticlesdynamical quasiparticles‘‘)) withwith

offoff--shell spectral functionsshell spectral functions (width, mass) defined by the DQPM(width, mass) defined by the DQPM

�� elastic and inelastic partonelastic and inelastic parton--parton interactions:parton interactions:

using the effective cross sections from the DQPM using the effective cross sections from the DQPM

�� q + qbar q + qbar (flavor neutral)(flavor neutral) <<=> => gluongluon (colored)(colored)

�� gluongluon + + gluongluon <=<=> > gluongluon (possible due to large spectral width)(possible due to large spectral width)

�� q + qbar q + qbar (color neutral)(color neutral) <=> hadron resonances<=> hadron resonances

�� selfself--generated meangenerated mean--field potential for quarks and gluons !field potential for quarks and gluons !

Hadronization: Hadronization: based on DQPM based on DQPM -- massive, offmassive, off--shell quarks and gluons shell quarks and gluons with with

broad spectralbroad spectral functions hadronize tofunctions hadronize to offoff--shell mesons and baryons:shell mesons and baryons:

gluons gluons �� q + qbar;q + qbar; q + qbar q + qbar �� meson (or string);meson (or string);

q + q +q q + q +q �� baryonbaryon (or string)(or string) (strings act as (strings act as ‚‚doorway statesdoorway states‘‘ for hadrons) for hadrons)

Hadronic phase: Hadronic phase: hadronhadron--string interactions string interactions –– offoff--shell HSDshell HSD

13


NPA831 (2009) 215; NPA831 (2009) 215; EEPJ ST PJ ST 168168 (2009) (2009) 33; ; NNPPA856A856 (2011) (2011) 162162..

PHSD: hadronization of a partonic fireballPHSD: hadronization of a partonic fireball

Consequences:Consequences:

��Hadronization:Hadronization: q+qq+qbarbar or 3q or 3qor 3q or 3qbarbar fuse to fuse to

color neutral hadrons (or strings)color neutral hadrons (or strings) which which subsequently subsequently decay into hadrons in adecay into hadrons in a

microcanonical fashion, i.e.microcanonical fashion, i.e. obeying all conservation laws obeying all conservation laws (i.e. 4(i.e. 4--momentum momentum

conservation, conservation, flavor current conservation)flavor current conservation) in each event!in each event!

�� Hadronization Hadronization yieldsyields an increase in total entropy San increase in total entropy S (i.e. more hadrons in the (i.e. more hadrons in the

final state than initial partons )final state than initial partons ) and not a decrease as in the simple and not a decrease as in the simple

recombination models!recombination models!

��OffOff--shell parton transportshell parton transport roughly leads a roughly leads a hydrodynamic evolution hydrodynamic evolution of the of the

partonic systempartonic system

E.g.E.g. time evolution of thetime evolution of the

partonic fireballpartonic fireball at initial temperature at initial temperature

1.7 T1.7 Tcc at at µµµµµµµµqq=0=0


NPA831 (2009) 215; NPA831 (2009) 215;

W. Cassing, W. Cassing, EEPJ ST PJ ST 168168 (2009) (2009) 3314

Bulk properties:Bulk properties:

rapidity, mrapidity, mTT--distributions,distributions,

multimulti--strange particle enhancement in Au+Austrange particle enhancement in Au+Au

Application to nucleusApplication to nucleus--nucleus collisionsnucleus collisions

energy balanceenergy balance

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Ep

Em E

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# [

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]

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t [fm/c]

�� Dramatic decrease ofDramatic decrease of partonic phase partonic phase with decreasing energywith decreasing energy

�� Pb+Pb, 160 A GeV: only aboutPb+Pb, 160 A GeV: only about 40% 40% of the converted energy goes to partons;of the converted energy goes to partons;

the rest is contained in the the rest is contained in the large hadronic corona and leading partonslarge hadronic corona and leading partons!!

Cassing & Bratkovskaya, NPA 831 (2009) 215Cassing & Bratkovskaya, NPA 831 (2009) 215

16

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rton

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ner

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ract

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t [fm/c]

partonic energy fraction vs energypartonic energy fraction vs energy

PHSD: Transverse mass spectraPHSD: Transverse mass spectra

Central Pb + Pb at SPS energiesCentral Pb + Pb at SPS energies

17

�� PHSD gives PHSD gives harder mharder mTT spectraspectra and works better than HSD and works better than HSD at high energiesat high energies

–– RHIC, SPS (and top FAIR, NICA) RHIC, SPS (and top FAIR, NICA)

�� however, at low SPS (and low FAIR, NICA) energies the effect ofhowever, at low SPS (and low FAIR, NICA) energies the effect of the partonic phase the partonic phase

decreases due to the decrease of the partonic fraction decreases due to the decrease of the partonic fraction

Central Au+Au at RHICCentral Au+Au at RHIC

W. Cassing & E. Bratkovskaya, NPA 831 (2009) 215W. Cassing & E. Bratkovskaya, NPA 831 (2009) 215

E. Bratkovskaya, W. Cassing, V. Konchakovski, O. Linnyk, E. Bratkovskaya, W. Cassing, V. Konchakovski, O. Linnyk,

NPA856 (2011) 162NPA856 (2011) 162

Centrality dependence of (multiCentrality dependence of (multi--)strange (anti)strange (anti--)baryons)baryons

�� enhanced production of (multienhanced production of (multi--) strange antibaryons in PHSD ) strange antibaryons in PHSD

relative to HSDrelative to HSD

strange strange

antibaryonsantibaryons

_ __ _

ΛΛΛΛΛΛΛΛ++ΣΣΣΣΣΣΣΣ00

multimulti--strange strange

antibaryonantibaryon

__

ΞΞΞΞΞΞΞΞ++

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HSD

PHSD

ΛΛΛΛ+ΣΣΣΣ0

NwoundN

wound

Pb+Pb, 158 A GeV, mid-rapidity _ _

Λ+ΣΛ+ΣΛ+ΣΛ+Σ0000

dN

/dy |

y=

0 / N

wou

nd

0 100 200 300 40010

-4

10-3

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PHSD NA57

NA49

ΞΞΞΞ−−−−

dN

/dy | y

=0 /

Nw

ound

________

ΞΞΞΞ++++

Pb+Pb, 158 A GeV, mid-rapidity

Nwound

Nwound

multimulti--strange strange

baryonbaryon

ΞΞΞΞΞΞΞΞ−−−−−−−−--

strange strange

baryonsbaryons

ΛΛΛΛΛΛΛΛ++ΣΣΣΣΣΣΣΣ00

Cassing & Bratkovskaya, NPA 831 (2009) 215Cassing & Bratkovskaya, NPA 831 (2009) 215

18

Elliptic flow vElliptic flow v22 vs. collision energy for Au+Auvs. collision energy for Au+Au

19

� v2 in PHSD is larger than in HSD due to the repulsive scalar mean-field

potential Us(ρ) for partons

� v2 grows with bombarding energy due to the increase of the parton fraction

V. Konchakovski, E. Bratkovskaya, W. Cassing, V. Toneev, V. VV. Konchakovski, E. Bratkovskaya, W. Cassing, V. Toneev, V. Voronyuk, oronyuk,

Phys. Rev. C 85 (2012) 011902 Phys. Rev. C 85 (2012) 011902

DileptonsDileptons

Electromagnetic probes: dileptons and photonsElectromagnetic probes: dileptons and photons

In-medium workshop, Giessen Joachim Stroth 5

Dilepton sources in HI collisionsDilepton sources in HI collisions

Dilepton sources: Dilepton sources:

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

�� from hadronic sources:from hadronic sources:

••direct decay of vector direct decay of 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,JJ/Ψ,Ψ/Ψ,Ψ/Ψ,Ψ/Ψ,Ψ/Ψ,Ψ/Ψ,Ψ/Ψ,Ψ/Ψ,Ψ‘‘) )

••Dalitz decay of mesons Dalitz decay of mesons

and baryons (and baryons (ππππππππ00,,ηηηηηηηη, , ∆∆∆∆∆∆∆∆,,……))

••correlated D+Dbar pairscorrelated D+Dbar pairs

••radiation from multiradiation from multi--meson reactions (meson reactions (ππππππππ++ππππππππ, , ππππππππ++ρρρρρρρρ, ,

ππππππππ++ωωωωωωωω, , ρρρρρρρρ++ρ ρ ρ ρ ρ ρ ρ ρ , , ππππππππ+a+a11) ) -- ‚‚44ππππππππ‘‘

�� Dileptons are Dileptons are an ideal probean ideal probe to study the to study the

properties of the hot and dense mediumproperties of the hot and dense medium

γγγγγγγγ**

gg γγγγγγγγ**

γγγγγγγγ**

qq l+

l--

γγγγγγγγ**

qq

qq

qq

qq

qqqq

gggg

qq

�� Dileptons are emitted from different stages of the reaction and Dileptons are emitted from different stages of the reaction and

not much effected by finalnot much effected by final--state interactionsstate interactions

22

Dileptons from SIS to FAIR/NICADileptons from SIS to FAIR/NICA

Dileptons : Dileptons : ‚‚freefree‘‘ vs. vs. ‚‚inin--mediummedium‘‘ scenarios (scenarios (collisional broadeningcollisional broadening ,,

collisional broadening +dropping masscollisional broadening +dropping mass)) for vector mesons for vector 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)

��enhancement enhancement of dilepton yield for 0.2<M<0.7 GeV and of dilepton yield for 0.2<M<0.7 GeV and

��reductionreduction at M~mat M~mρ/ω ρ/ω ρ/ω ρ/ω ρ/ω ρ/ω ρ/ω ρ/ω for all energies from SIS to FAIR/NICA!for all energies from SIS to FAIR/NICA!

0.0 0.2 0.4 0.6 0.8 1.0 1.2

10-5

10-4

10-3

10-2

10-1

100

101

102

M [GeV/c2]

HSD:

free

coll. broad.

coll. broad. + drop. mass.

Au+Au, 10 A GeV, b=0.5 fm

dN

/dM

[1

/GeV

/c2 ]

0.0 0.2 0.4 0.6 0.8 1.0 1.2

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

M [GeV/c2]

HSD:

free

coll. broad.



dN

/dM

[1

/GeV

/c2 ]

0.0 0.2 0.4 0.6 0.8 1.0 1.2

10-5

10-4

10-3

10-2

10-1

100

101

102

M [GeV/c2]

HSD:

free

coll. broad.



dN

/dM

[1

/GeV

/c2 ]

0.0 0.2 0.4 0.6 0.8 1.0 1.2

10-5

10-4

10-3

10-2

10-1

100

101

102

M [GeV/c2]

HSD:

free

coll. broad.



dN

/dM

[1

/GeV

/c2 ]

0.0 0.2 0.4 0.6 0.8 1.0 1.2

10-5

10-4

10-3

10-2

10-1

100

101

102

M [GeV/c2]

HSD:

free

coll. broad.



dN

/dM

[1

/GeV

/c2 ]

0.0 0.2 0.4 0.6 0.8 1.0 1.2

10-5

10-4

10-3

10-2

10-1

100

101

102

M [GeV/c2]

HSD:

free

coll. broad.



dN

/dM

[1

/GeV

/c2 ]

Dileptons at SPS: NA60Dileptons at SPS: NA60

�� Mass region above 1 GeV is dominated Mass region above 1 GeV is dominated

by by partonic radiationpartonic radiation !!

Acceptance corrected NA60 dataAcceptance corrected NA60 data

O. Linnyk, E.B., V. Ozvenchuk, W. Cassing O. Linnyk, E.B., V. Ozvenchuk, W. Cassing

and C.and C.--M. Ko, PRC 84 (2011) M. Ko, PRC 84 (2011) 054917054917

�� Contributions of Contributions of ““44ππππππππ”” channels channels

((radiation from multiradiation from multi--meson reactions) meson reactions)

are are smallsmall

Dileptons at SPS: NA60Dileptons at SPS: NA60



Acceptance corrected NA60 dataAcceptance corrected NA60 data

NA60: mNA60: mTT spectraspectra

��Inverse slope parameter TInverse slope parameter Teff eff for for

dilepton spectra vs NA60 datadilepton spectra vs NA60 data

Conjecture: Conjecture:

�� spectrum from sQGP is softer than from hadronic phasespectrum from sQGP is softer than from hadronic phase since quarksince quark--antiquark antiquark

annihilation occurs dominantly before the collective radial flowannihilation occurs dominantly before the collective radial flow has developed (cf. has developed (cf.

NA60)NA60)



Dileptons at RHIC: PHENIXDileptons at RHIC: PHENIX

PHENIX: Au+AuPHENIX: Au+AuPHENIX: ppPHENIX: pp

•• HSD provides a HSD provides a good description of pp datagood description of pp data

•• Standard inStandard in--medium effects of vector medium effects of vector

mesons mesons ---- compatible with the NA60 and compatible with the NA60 and

CERES data at SPS CERES data at SPS –– do not explain the do not explain the

large enhancement observed by PHENIXlarge enhancement observed by PHENIX in in

the invariant mass from 0.2 to 0.5 GeV in the invariant mass from 0.2 to 0.5 GeV in

Au+Au collisions at s Au+Au collisions at s 1/21/2=200 GeV (relative to =200 GeV (relative to

pp collisions)pp collisions)0.0 0.2 0.4 0.6 0.8 1.0 1.2

10-5

10-4

10-3

10-2

10-1

0.0 0.2 0.4 0.6 0.8 1.0 1.210

-6

10-5

10-4

10-3

10-2

10-1

HSD:

free spectral functions

collisional broadening

dropp. mass + coll. broad.

PHENIX

min. bias Au+Au, s1/2

=200 GeV

M [GeV/c2]

1/N

evt d

N/d

M [1

/(G

eV/c

2 )]

HSD (free spectral functions):

sum

ππππ0 ηηηη ηηηη'

ρρρρ ωωωω φφφφ

c + c −>−>−>−> e++e

−−−− (PYTHIA)

PHENIX

min. bias Au+Au, s1/2

=200 GeV

M [GeV/c2]

1/N

evt d

N/d

M [1

/(G

eV/c

2 )]

0.0 0.2 0.4 0.6 0.8 1.0 1.210

-8

10-7

10-6

10-5

10-4

10-3

PHENIX HSD:

sum

ππππ0 ηηηη ηηηη'

ρρρρ ωωωω φφφφ

c+c −> −> −> −> e++e

−−−− (PYTHIA)

M [GeV/c2]

p+p, s1/2

=200 GeV

1/N

evt d

N/d

M [1

/(G

eV/c

2 )]

E. B., W. Cassing, O. Linnyk, PLB 670 (2009) 428E. B., W. Cassing, O. Linnyk, PLB 670 (2009) 428

Dileptons at RHIC: data vs. theor. modelsDileptons at RHIC: data vs. theor. models

PHENIX:PHENIX:

Au+AuAu+Au

�� PHENIX dilepton puzzle ?!PHENIX dilepton puzzle ?!

PHENIX: dileptons from partonic channelsPHENIX: dileptons from partonic channels

•• The The partonic channelspartonic channels fill up the fill up the

discrepancy between the hadronic discrepancy between the hadronic

contributions and the data for M>1 GeVcontributions and the data for M>1 GeV

••The The excess excess over the considered over the considered

mesonic sources for M=0.15mesonic sources for M=0.15--0.6 GeV 0.6 GeV

is not explained by the QGP radiation is not explained by the QGP radiation

as incorporated presently in PHSDas incorporated presently in PHSD

O. Linnyk, W. Cassing, J. Manninen, E.B. and C.O. Linnyk, W. Cassing, J. Manninen, E.B. and C.--M. Ko, M. Ko,

PRC 85 (2012) 024910PRC 85 (2012) 024910

PHENIX: mass spectraPHENIX: mass spectra

�� Peripheral collisionsPeripheral collisions are well described, however, are well described, however, central central fail!fail!


PRC 85 (2012) 024910PRC 85 (2012) 024910

•• The The lowest and highest masslowest and highest mass bins are described bins are described very wellvery well

•• Underestimation of pUnderestimation of pTT data for 100<M<750 MeV bins consistent with dN/dM data for 100<M<750 MeV bins consistent with dN/dM

•• The The ‘‘missing sourcemissing source’’(?) is located at low p(?) is located at low pTT !!

PHENIX: pPHENIX: pTT spectraspectra


PRC 85 (2012) 024910PRC 85 (2012) 024910

STAR: mass spectraSTAR: mass spectra

�� STAR data are well described!STAR data are well described!O. Linnyk, W. Cassing, J. Manninen, E.B. and C.O. Linnyk, W. Cassing, J. Manninen, E.B. and C.--M. Ko, M. Ko,

PRC 85 (2012) 024910PRC 85 (2012) 024910

32

Summary Summary

••PartonParton--HadronHadron--StringString--Dynamics (PHSD)Dynamics (PHSD) theory provides a consistent theory provides a consistent

description of the phase transition to the QGP in heavydescription of the phase transition to the QGP in heavy--ion collisions.ion collisions.

••InIn--medium effects can be observed in dilepton spectra at medium effects can be observed in dilepton spectra at all energiesall energies from SIS to from SIS to

RHICRHIC

••The dilepton data fromThe dilepton data from NA60 NA60 at SPS energies are better described within offat SPS energies are better described within off--

shell HSD/PHSD, if a shell HSD/PHSD, if a collisional broadeningcollisional broadening of vector mesons is assumed.of vector mesons is assumed.

••The yield of dilepton pairs at masses The yield of dilepton pairs at masses above 1 GeVabove 1 GeV indicates the presence of the indicates the presence of the

strongly interacting QGPstrongly interacting QGP and is described by the interactions of dynamical and is described by the interactions of dynamical

quasiparticlesquasiparticles

•• Neither the incorporated hadronic nor partonic sources account Neither the incorporated hadronic nor partonic sources account for the for the

enhancement observed by enhancement observed by PHENIX PHENIX in the invariant mass from 0.2 to 0.6 GeV in in the invariant mass from 0.2 to 0.6 GeV in

Au+Au collisions at sAu+Au collisions at s1/21/2=200 GeV (relative to pp collisions)=200 GeV (relative to pp collisions)

•• STAR dataSTAR data are well reproduced by PHSD within the STAR acceptanceare well reproduced by PHSD within the STAR acceptance

Wolfgang Cassing Wolfgang Cassing (Giessen Univ.)(Giessen Univ.)

Volodya Konchakovski Volodya Konchakovski (Giessen Univ.)(Giessen Univ.)

Olena Linnyk Olena Linnyk (Giessen Univ.)(Giessen Univ.)

Elena BratkovskayaElena Bratkovskaya (FIAS & ITP Frankfurt Univ.)(FIAS & ITP Frankfurt Univ.)

Vitalii Ozvenchuk Vitalii Ozvenchuk (HGS(HGS--HIRe, FIAS & ITP Frankfurt Univ.)HIRe, FIAS & ITP Frankfurt Univ.)

+ Rudy Marty+ Rudy Marty (SUBATECH(SUBATECH��FIAS, Frankfurt Univ.)FIAS, Frankfurt Univ.)

External Collaborations:External Collaborations:SUBATECH, Nantes Univ. :SUBATECH, Nantes Univ. :

JJöörg Aichelin rg Aichelin

Christoph HartnackChristoph Hartnack

PolPol--Bernard GossiauxBernard Gossiaux

Texas A&M Univ.:Texas A&M Univ.:

CheChe--Ming KoMing Ko

JINR, Dubna:JINR, Dubna:

Vadim Voronyuk Vadim Voronyuk

Viatcheslav ToneevViatcheslav Toneev

Kiev Univ.:Kiev Univ.:

Mark GorensteinMark Gorenstein

Barcelona Univ.Barcelona Univ.

Laura Tolos, Angel RamosLaura Tolos, Angel Ramos

PHSD group PHSD group

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