Lecture 14Lecture 14Signatures of QuarkSignatures of Quark--Gluon Plasma Gluon Plasma

WS2010/11WS2010/11: : ‚‚Introduction to Nuclear and Particle PhysicsIntroduction to Nuclear and Particle Physics‘‘

From Big Bang to Formation of the Universe

Can we go back in time ?

time 3 min nucleonsdeuteronsαααα−−−−particles

10-3sec quarks gluonsphotons

T~180 MeV

300000 years

atoms

15 Mrd years

our Universe

... back in time

1 event: Au+Au

‚Re‚Re--create‘ the create‘ the Big Bang Big Bang conditions:conditions:matter at high temperature matter at high temperature and pressureand pressure

such thatsuch thatnucleons/mesons decouple to nucleons/mesons decouple to quarks and gluons quarks and gluons ----QuarkQuark--GluonGluon--PlasmaPlasma

‚Little Bangs‘ in the ‚Little Bangs‘ in the Laboratory : Laboratory : HeavyHeavy--ion collisions at ion collisions at ultrarelativistic energiesultrarelativistic energies

QGPQGP

nucleonsnucleons

HeavyHeavy--ion acceleratorsion accelerators

1 event: Au+Au

SuperSuper--ProtonProton--Synchrotron Synchrotron –– SPS SPS --(CERN): (CERN): Pb+Pb at 160 A GeVPb+Pb at 160 A GeV

RelativisticRelativistic--HeavyHeavy--IonIon--Collider Collider -- RHIC RHIC --(Brookhaven): (Brookhaven): Au+Au at 21.3 A TeVAu+Au at 21.3 A TeV

STAR detector at RHICSTAR detector at RHIC

Future facilities:Future facilities: FAIR (GSI), NICA (Dubna)FAIR (GSI), NICA (Dubna)

Large Hadron ColliderLarge Hadron Collider –– LHC LHC --(CERN): (CERN): Pb+Pb at 574 A TeVPb+Pb at 574 A TeV

3.8 km3.8 km

The QGP in Lattice QCDThe QGP in Lattice QCD

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Lattice QCD:Lattice QCD:energy density versus temperatureenergy density versus temperatureQQuantum uantum CCromo romo DDynamics :ynamics :

predicts strong increase ofpredicts strong increase ofthe the energy density energy density εεεεεεεε at critical at critical temperature temperature TTC C ~170 MeV~170 MeV

PossiblePossible phase transition phase transition fromfromhadronic to hadronic to partonic matter partonic matter (quarks, gluons) at critical energy (quarks, gluons) at critical energy densitydensity εεεεεεεεCC ~1 GeV/fm~1 GeV/fm3 3

Critical conditions Critical conditions -- εεεεεεεεCC ~1 GeV/fm~1 GeV/fm33 , T, TC C ~170 MeV ~170 MeV -- can be reached in can be reached in heavyheavy--ion experimentsion experiments at bombarding energiesat bombarding energies > 5 GeV/A> 5 GeV/A

‚Little Bangs‘ in the Laboratory

time

How can we proove that an equilibrium QGP has been How can we proove that an equilibrium QGP has been created in central Au+Au collisions ?! created in central Au+Au collisions ?!

•• Strangeness enhancement Strangeness enhancement •• MultiMulti--strange particle enhancement in A+A strange particle enhancement in A+A •• Charm suppressionCharm suppression•• Collective flow (vCollective flow (v11, v, v22))•• Thermal dileptonsThermal dileptons•• Jet quenching and angular correlationsJet quenching and angular correlations•• High pHigh pTT suppression of hadronssuppression of hadrons•• Nonstatistical event by event fluctuations and correlations Nonstatistical event by event fluctuations and correlations •• ... ...

Experiment: Experiment: measures measures final hadrons and leptonsfinal hadrons and leptons

Signals of the phase transition:Signals of the phase transition:

How to learn about How to learn about physics from data?physics from data?

Compare with theory!Compare with theory!

•• Statistical models:Statistical models:basic assumptionbasic assumption: system is described by a (grand) canonical ensemble of : system is described by a (grand) canonical ensemble of nonnon--interacting fermions and bosons in interacting fermions and bosons in thermal and chemical equilibriumthermal and chemical equilibrium

[ [ --:: no dynamics]no dynamics]•• Ideal hydrodynamical models:Ideal hydrodynamical models:basic assumptionbasic assumption: conservation laws + equation of state; assumption of : conservation laws + equation of state; assumption of local thermal and chemical equilibriumlocal thermal and chemical equilibrium

[ [ --:: -- simplified dynamics]simplified dynamics]•• Transport models:Transport models:based on transport theory of relativistic quantum manybased on transport theory of relativistic quantum many--body systems body systems --offoff--shell Kadanoffshell Kadanoff--Baym equations for the GreenBaym equations for the Green--functions Sfunctions S<<

hh(x,p) in (x,p) in phasephase--space representation. space representation. Actual solutions:Actual solutions: Monte Carlo simulations with Monte Carlo simulations with a large number of testa large number of test--particlesparticles

[[+: +: full dynamics | full dynamics | --:: very complicated]very complicated]

Basic models for heavyBasic models for heavy--ion collisions ion collisions

Microscopic transport models provide a unique Microscopic transport models provide a unique dynamicaldynamical description description of of nonequilibriumnonequilibrium effects in heavyeffects in heavy--ion collisions ion collisions

Models of heavyModels of heavy--ion collisionsion collisions

transport

hydro ?hydro ?

thermal+expansion ?thermal+expansion ?

thermal modelthermal model

finalfinalinitialinitial

HSDHSD –– HHadronadron--SStringtring--DDynamics transport approachynamics transport approachUrQMDUrQMD –– UUltraltra--rrelativisticelativistic--QQuantumuantum--MMolecularolecular--DDynamics ynamics

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

with collision termswith collision 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 stringstring formation and decay formation and decay

••Implementation of Implementation of detailed balance detailed balance on the level of 1on the level of 1<<<<<<<<−−−−−−−−>>>>>>>>22and 2and 2<<<<<<<<−−−−−−−−>>>>>>>>2 reactions (+ 22 reactions (+ 2<<<<<<<<−−−−−−−−>>>>>>>>n n multimulti--meson fusion reactionsmeson fusion reactions in HSD)in HSD)

Basic concept of HSD & UrQMDBasic concept of HSD & UrQMD

(((( )))) (((( )))) ),...,f,f(fI,t)p,r(fHHt M21colliprrp ====

∇∇∇∇∇∇∇∇−−−−∇∇∇∇∇∇∇∇++++∂∂∂∂∂∂∂∂

Full collision term consists of Full collision term consists of ~10000 different two particle ~10000 different two particle combinationscombinations

Nucleon transport in N,Nucleon transport in N,π,∆π,∆π,∆π,∆π,∆π,∆π,∆π,∆ system : Dfsystem : DfNN=I=Icollcoll

•• hadronshadrons -- baryons and mesons including excited states (resonances)baryons and mesons including excited states (resonances)•• stringsstrings –– excited color singlet states (qq excited color singlet states (qq -- q) or (q q) or (q –– qbar)qbar)

Based on the LUND string model& perturbative QCD via PYTHIA

•• leading quarksleading quarks (q, qbar) & (q, qbar) & diquarksdiquarks(q(q--q, qbarq, qbar--qbar) qbar)

NOT included in the transport models NOT included in the transport models presented herepresented here ::oo no explicit no explicit partonparton--parton interactionsparton interactions (i.e. between quarks and gluons) (i.e. between quarks and gluons)

outside strings!outside strings!oo no explicit no explicit phase transitionphase transition from hadronic to partonic degrees of freedomfrom hadronic to partonic degrees of freedomoo QCD EoS for partonic phaseQCD EoS for partonic phase

Degrees of freedom in HSD & UrQMDDegrees of freedom in HSD & UrQMD

Description of elementary reactions in HSD & UrQMDDescription of elementary reactions in HSD & UrQMD

Low energy collisions:Low energy collisions:•• binary 2binary 2<<<<<<<<−−−−−−−−>2>2>2>2>2>2>2>2 andand22<<<<<<<<−−−−−−−−>>>>>>>>3 reactions 3 reactions •• formation and formation and decay of baryonic and decay of baryonic and mesonic resonancesmesonic resonances

BB BB <<<<<<<<−−−−−−−−> > > > > > > > B´B´B´B´BB BB <<<<<<<<−−−−−−−−> > > > > > > > B´B´mB´B´m

mB mB <<<<<<<<−−−−−−−−> > > > > > > > m´B´ m´B´ mB mB <<<<<<<<−−−−−−−−> > > > > > > > B´B´

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 particlesdescribed by described by string formation and string formation and decaydecay

•• very good description of particle production invery good description of particle production in pp, pA reactionspp, pA reactions•• unique description of nuclear dynamicsunique description of nuclear dynamics fromfrom low low (~100 MeV)(~100 MeV) to to

ultrarelativistic ultrarelativistic (21.3 TeV) energies(21.3 TeV) energies

HSD & UrQMD HSD & UrQMD –– microscopical models for heavymicroscopical models for heavy--ion reactionsion reactions

HSDHSD1999 predictions1999 predictions

HSDHSD1999 predictions1999 predictions

Goal:Goal: microscopic transport description of themicroscopic transport description of thepartonic partonic andand hadronic phasehadronic phase

Problems:Problems:

How to model a QGP phase in line with lQCD data?How to model a QGP phase in line with lQCD data?

Approaches so far:Approaches so far: partonic cascades based on pQCD with partonic cascades based on pQCD with mmassless quarks and gluons (gives an equation of state not assless quarks and gluons (gives an equation of state not consistent with lattice QCD) consistent with lattice QCD)

How to solve the hadronization problem?How to solve the hadronization problem?

Previous ideas:Previous ideas: recombination models recombination models

quark recombination

hadronization

partonic phasepartonic phase hadronic phasehadronic phase

Entropy puzzle: Entropy puzzle: the the particle particle number decreases drastically in the number decreases drastically in the hadronizationhadronization by recombinationby recombination, i.e., i.e.recombination violates the 2nd law recombination violates the 2nd law of thermodynamics : Sof thermodynamics : SH H < S< SQQ

From hadrons to partonsFrom hadrons to partons

In order to study of the In order to study of the phase transitionphase transition from from hadronic to partonic matter hadronic to partonic matter –– QuarkQuark--GluonGluon--PlasmaPlasma ––we we need need a a consistent transport model withconsistent transport model withexplicit 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 freedomlQCD EoS lQCD EoS for partonic phasefor partonic phase

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

QGP phase QGP phase described by input from thedescribed by input from the

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 thepartonic 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

PHSD PHSD -- basic conceptsbasic concepts

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‘‘)) withwithoffoff--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 q + qbar (flavor neutral) <=> gluon (colored) gluon + gluon <=> gluon (possible due to large spectral width) q + qbar (color neutral) <=> hadron resonances

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

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

17

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 furtheron decay to hadrons in which furtheron decay to hadrons in aa microcanonical fashion, i.e.microcanonical fashion, i.e. obeying all conservation laws obeying all conservation laws (i.e. 4(i.e. 4--momentum conservation, momentum 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 (i.e. more hadrons in the final state than initial partons )hadrons in the final state than initial partons ) and not a decrease as in and not a decrease as in the simple recombination models!the simple recombination models!

OffOff--shell parton transportshell parton transport roughly leads a roughly leads a hydrodynamic evolutionhydrodynamic evolutionof the partonic systemof the partonic system

E.g.E.g. time evolution of thetime evolution of thepartonic fireballpartonic fireball at initial at initial temperature 1.7 Ttemperature 1.7 Tcc at at µµµµµµµµqq=0=0

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) 3318

Our ultimate goals:Our ultimate goals:

•• 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 properties of hadrons at high baryon density and temperatureat high baryon density and temperature

The phase diagram of QCDThe phase diagram of QCD

DileptonsDileptons

Aim I. Study of inAim I. Study of in--medium effects medium effects within transport approacheswithin transport 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 propertiesin 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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R. Rapp:R. Rapp: ρρρρρρρρ meson spectral functionmeson spectral function

•• Accounting ofAccounting of inin--medium effects medium effects with with medium dependent spectral functionsmedium dependent spectral functions requires requires offoff--shell transport models ! shell transport models !

Modelling of inModelling of in--medium spectral functions for medium spectral functions for vector mesonsvector mesons

InIn--medium scenarios:medium scenarios:

dropping mass collisional broadening dropping mass collisional broadening dropping mass + coll. broad.dropping mass + coll. broad.

m*=mm*=m00(1(1--α ρ/ρα ρ/ρα ρ/ρα ρ/ρα ρ/ρα ρ/ρα ρ/ρα ρ/ρ00000000) ) ΓΓΓΓΓΓΓΓ(M,(M,ρρρρρρρρ)=)=ΓΓΓΓΓΓΓΓvacvac(M)+(M)+ΓΓΓΓΓΓΓΓCBCB(M,(M,ρρρρρρρρ) m* & ) m* & ΓΓΓΓΓΓΓΓCBCB(M,(M,ρ)ρ)ρ)ρ)ρ)ρ)ρ)ρ)

Collisional widthCollisional width ΓΓΓΓΓΓΓΓCBCB(M,(M,ρρρρρρρρ) = ) = γ ρ <υ σγ ρ <υ σγ ρ <υ σγ ρ <υ σγ ρ <υ σγ ρ <υ σγ ρ <υ σγ ρ <υ σVNVNtottot>>>>>>>>

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spectral functionspectral function : narrowing: narrowing

Consequences when Consequences when increasing the baryon density increasing the baryon density ρ:ρ:ρ:ρ:ρ:ρ:ρ:ρ:

pole position mpole position m00 : unchanged : unchanged

spectral functionspectral function : broadening: broadening

pole position mpole position m00 : shift: shift to low M to low M

spectral functionspectral function : broadening: broadening

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

Dileptons are emitted from different stages of the Dileptons are emitted from different stages of the reaction and reaction and not effected by finalnot effected by final--state interactionsstate interactions

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, , ∆∆∆∆∆∆∆∆,…),…)

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

Dilepton cocktailDilepton cocktail

••All particles decaying to dileptons All particles decaying to dileptons are are first produced in BB, mB or mm first produced in BB, mB or mm collisionscollisions

heav

yhe

avy --

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colli

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sio

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llisi

ons

p+p, p+A collisionsp+p, p+A collisions

ππππππππ+p, +p, ππππππππ+A collisions+A collisions

Dilepton spectra from heavy-ion collisions Dilepton spectra from heavyDilepton spectra from heavy--ion collisions ion collisions

Dileptons (e+eDileptons (e+e-- or or µµµµµµµµ++µµµµµµµµ-- pairs)pairs) are an are an ideal probeideal probe for vector meson for vector meson spectroscopy in the spectroscopy in the nuclear mediumnuclear medium and for the nuclear dynamics !and for the nuclear dynamics !

CERES, HELIOSCERES, HELIOS--3 data (1995)3 data (1995)

No medium effects:No medium effects: too much yield in the too much yield in the ρ ρ ρ ρ ρ ρ ρ ρ peakpeak missing yield around M~0.5 GeVmissing yield around M~0.5 GeV

InIn--medium spectral function:medium spectral function:works rather wellworks rather well

Dilepton spectra at Dilepton spectra at SIS energies SIS energies (BEVALAC and HADES) show (BEVALAC and HADES) show similar similar inin--medium modificationmedium modification of vector meson spectral functionsof vector meson spectral functions

Dileptons: NA60 Dileptons: NA60 ((µµµµµµµµ++µµµµµµµµ-- spectra)spectra)

High precision NA60 data allow to distinguish among inHigh precision NA60 data allow to distinguish among in--medium models!medium models!Clear evidence for a broadening of the Clear evidence for a broadening of the ρ ρ ρ ρ ρ ρ ρ ρ spectral function!spectral function!

oppositeopposite--side dimuonsside dimuonscombinatorial backgroundcombinatorial background

resulting signalresulting signal

Excess spectrum = Excess spectrum = resulting signal resulting signal ––‚‚cocktailcocktail‘‘ sourcessources

Exp. data vs theory (Rapp et. al.)Exp. data vs theory (Rapp et. al.)-- models for models for ρρρρρρρρ spectral function:spectral function: vacuum s.f.vacuum s.f. dropping mass (Brown/Rho)dropping mass (Brown/Rho) coll. broad. (Rapp/Wambach)coll. broad. (Rapp/Wambach)

NA60 data vs. HSD transportNA60 data vs. HSD transport

•• NA60 data are better NA60 data are better described bydescribed by inin--medium medium scenario with collisional scenario with collisional broadening broadening

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

•• High M tail not reproduced in HSD High M tail not reproduced in HSD NonNon--hadronichadronic origin? origin?

HSD HSD –– full full offoff--shell propagationshell propagationof inof in--medium spectral functions medium spectral functions through the hadronic mediumthrough the hadronic medium

-- models for models for ρρρρρρρρ spectral function:spectral function: vacuum spectral functionvacuum spectral function dropping mass (Brown/Rho)dropping mass (Brown/Rho) coll. broad. (Rapp/Wambach)coll. broad. (Rapp/Wambach)

Dileptons at SPS: CERES (eDileptons at SPS: CERES (e++ee-- spectra)spectra)

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<dN

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•• CERES data are better described byCERES data are better described by inin--medium scenario with collisional broadening medium scenario with collisional broadening

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1.8

CERES (2008 data): 'ρρρρ'

HSD: ρρρρ: free s.f. ρρρρ: coll. broad. total yield − − − − HSD 'cocktail'

x 10-6Pb+Au, 160 A GeV, 7%

pT> 200 MeV/cθθθθe+e-> 35 mrad2.1 < ηηηη < 2.65

<dN

e+ e-(tot

al-'c

ockt

ail')

/dM

> / <

Nch

> [(

100

MeV

/c2 )-1

]M [GeV/c2]

Dileptons at RHICDileptons at RHIC

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

•• Dilepton cocktail Dilepton cocktail provides aprovides a good description of pp data good description of pp data as well asas well as peripheral Au+Au data, peripheral Au+Au data,

however,however, fails in describing the central bins!fails in describing the central bins!

‚‚excessexcess‘‘

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

PHENIX:PHENIX:Au+AuAu+Au

•• Models provide a Models provide a good description of pp datagood description of pp data•• Standard inStandard in--medium effects of vector mesons medium effects of vector mesons ---- compatible with the NA60 and compatible with the NA60 and CERES data at SPS CERES data at SPS –– do not explain the large enhancement observed by do not explain the large enhancement observed by PHENIXPHENIX in the invariant mass from 0.2 to 0.5 GeV in central Au+Au collin the invariant mass from 0.2 to 0.5 GeV in central Au+Au collisions isions at s at s 1/21/2=200 GeV (relative to pp collisions) =200 GeV (relative to pp collisions) PHENIX dilepton puzzle ?!PHENIX dilepton puzzle ?!

QGP radiation QGP radiation -- PHSDPHSD

0.0 0.2 0.4 0.6 0.8 1.0

10-5

10-4

10-3

10-2

10-1

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.510-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

ππππ0 ηηηη ηηηη' ρρρρ ωωωω φφφφ ∆∆∆∆ a1 D

Au+Au, s1/2=200 GeV, 0-10% central

M [GeV/c2]

1/N

evt d

N/d

M [

1/(G

eV/c

2 )] PHENIX HSD PHSD q+qbar->γγγγ*

q+qbar->γγγγ*+g q+g->γγγγ*+q

M [GeV/c2]

•• The The contribution contribution of the QGP to theof the QGP to the dileptondilepton radiation clearly increases with radiation clearly increases with centralitycentrality..•• There is a large There is a large discrepancy discrepancy between the data and PHSD for M=0.15between the data and PHSD for M=0.15--0.70.7 GeVGeV. . •• However, However, partonicpartonic channels dominate the observed yield at high masses !channels dominate the observed yield at high masses !

O. LinnykO. Linnyk

PHENIX dilepton puzzle ?PHENIX dilepton puzzle ?

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

Strange particlesStrange particlesStrange particles

Mesons:( ) ( )( ) ( )( ) ( )( ) ( ) GeV 0.892m sdKsdK

suKsuK

GeV 0.494m sdKsdK

suKsuK

K

0*0*

**

K

00

=

=−+

−+

Baryons:Baryons:

( )( ) ( ) ( )( ) ( )( ) GeV 1.672msss

GeV 1.315mdssuss

GeV 1.189mddsuusuds

GeV 1.116muds

0

0

0

=

=

=

=

−

−

−+

Strangeness |S|=1Strangeness |S|=1

Strangeness S= Strangeness S= --11

S= S= --22

S= S= --33

Strangeness production in A+A collisionsStrangeness production in A+A collisions

• Initially: no strangeness

• Finally: = strange particles

• How can strangeness be produced?

pairsss,

•• Strangeness Strangeness production in a hadronic world (at low energy):production in a hadronic world (at low energy):N+N N+N −−−−−−−−> > > > > > > > N+N+Λ+Λ+Λ+Λ+Λ+Λ+Λ+Λ+K requires K requires ∆∆∆∆∆∆∆∆E = 2ME = 2MNN--(M(MKK+M+MΛΛΛΛΛΛΛΛ+M+MNN)) =670 MeV=670 MeVπ+π+π+π+π+π+π+π+N N −−−−−−−−> Λ+> Λ+> Λ+> Λ+> Λ+> Λ+> Λ+> Λ+K K ∆∆∆∆∆∆∆∆E = (ME = (Mππππππππ+M+MNN))--(M(MKK+M+MΛΛΛΛΛΛΛΛ)) =535 MeV=535 MeV

•• Strangeness production in a QGP:Strangeness production in a QGP:bare mass of strange quark mbare mass of strange quark mSS~ 130 MeV~ 130 MeV=> => ss--sbar pair production sbar pair production

by by qq--qbar annihilationqbar annihilation q+qbar q+qbar −−−−−−−−>>>>>>>>s+sbars+sbarneeds only needs only ∆∆∆∆∆∆∆∆E=260 MeVE=260 MeV

=> s=> s--sbar pair can be also produced by sbar pair can be also produced by gluon fusion g+g gluon fusion g+g −−−−−−−−>>>>>>>>s+sbars+sbar

Strong enhancement of strangeness production in a QGP !Strong enhancement of strangeness production in a QGP !RafelskiRafelski--Müller: Phys. Rev. Lett. 48 (1982) 1066Müller: Phys. Rev. Lett. 48 (1982) 1066

=> => strangeness enhancement strangeness enhancement increasincreaseses with strangeness contentwith strangeness content ––ststrongerronger effect for effect for multimulti--strangestrange hadronshadrons ΞΞΞΞΞΞΞΞ(uss), (uss), ΩΩΩΩΩΩΩΩ(sss)(sss)

How strangeness can be produced in QGP ?How strangeness can be produced in QGP ?

Strangeness enhancement at Strangeness enhancement at SPSSPS energiesenergies

Enhancement grows:Enhancement grows: with the with the number of wounded nucleonsnumber of wounded nucleons (centrality)(centrality) with the with the number strange valence quarksnumber strange valence quarks: multi: multi--strange particles strange particles ΞΞΞΞΞΞΞΞ(uss) and (uss) and ΩΩΩΩΩΩΩΩ(sss)(sss) are stronger enhanced for central collisionsare stronger enhanced for central collisions

Experimental observations

Strangeness enhancement at RHIC energiesStrangeness enhancement at RHIC energies

Experiment Experiment ΞΞΞΞΞΞΞΞ and and ΩΩΩΩΩΩΩΩ enhancement for central collisions !enhancement for central collisions !

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 compare to HSDcompare to HSD

strange strange antibaryonsantibaryons

_ __ _ΛΛΛΛΛΛΛΛ++ΣΣΣΣΣΣΣΣ00

multimulti--strange strange antibaryonantibaryon

__ΞΞΞΞΞΞΞΞ++

0 100 200 300 4000.00

0.01

0.02

0.03

0.04

0.05

0.06

0 100 200 300 4000.000

0.002

0.004

0.006

0.008

0.010

NA57NA49

HSD PHSD

ΛΛΛΛ+ΣΣΣΣ0

NwoundN

wound

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

Λ+ΣΛ+ΣΛ+ΣΛ+Σ0000

dN/d

y | y=

0 / N

wou

nd

0 100 200 300 40010-4

10-3

10-2

0 100 200 300 400

10-4

10-3

HSD 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

Collective flow (vCollective flow (v11, v, v22))in Au+Auin Au+Au

x

z

Directed flow v1 & elliptic flow v2Directed flow vDirected flow v1 1 & elliptic flow v& elliptic flow v22

( )

>+−

=<

>=<

+++=

22

22

yx

yx2

T

x1

21TTTT

pppp

v

ppv

...)cos(22v)cos(2v121

dpdypdN

ddpdypdN ϕϕ

ϕ

v2 = 7%, v1=0

v2 = 7%, v1=-7%

v2 = -7%, v1=0

Out

-of-

plan

e

In-plane

Y

X

directed flowdirected flow

elliptic flow elliptic flow

VV2 2 > 0 > 0 indicates indicates inin--planeplane emission of particlesemission of particles

VV2 2 < 0 < 0 corresponds to a corresponds to a squeezesqueeze--out out perpendicular perpendicular to the reaction plane (to the reaction plane (outout--ofof--planeplane emission)emission)

x

zNon central Au+Au collisions :interaction between constituents leads to apressure gradient => spatial asymmetry is converted to an asymmetry in momentum space => collective flow

Y

0.1 1 10

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

RBUU (Munich), potential RBUU (Giessen), potential RBUU (Giessen), cascadeGiBUU, potentialGBUU, cascade

Au+Au, mid-rapidity, semi-centralprotons

EOS/ E895/ E877 FOPI/ Plastic Ball/ LAND/ MSU

v 2

Ebeam [GeV]

Collective flow: vCollective flow: v22 excitation function (SISexcitation function (SIS--AGS)AGS)

Proton vProton v22 at at low energylow energy shows sensitivity to the shows sensitivity to the nucleon potentialnucleon potential.. Cascade Cascade codes fail to describe the exp. data.codes fail to describe the exp. data. AGSAGS energies: energies: transitiontransition from squeezefrom squeeze--out to inout to in--plane elliptic flowplane elliptic flow

Collective flow: vCollective flow: v22 excitation functionexcitation function

vv2 2 excitation functions from the stringexcitation functions from the string--hadronic transport model UrQMD: hadronic transport model UrQMD: low energies low energies -- sensitivity to the sensitivity to the nucleon potentialnucleon potential high energieshigh energies -- missing vmissing v2 2 -- QGP pressure?! QGP pressure?!

Elliptic flow v2 in Au+Au at RHIC Elliptic flow vElliptic flow v2 2 in Au+Au at RHIC in Au+Au at RHIC

0 50 100 150 200 250 300 350 4000.00

0.02

0.04

0.06

0.08

0.10

PHOBOS HSD

Au+Au, s1/2=200 GeVcharged particles

|ηηηη|<1

v 2

-6 -4 -2 0 2 4 60.00

0.01

0.02

0.03

0.04

0.05

0.06v 2

Apart

PHOBOS HSD

Au+Au, s1/2=200 GeVcharged particles

v 2

ηηηη

•• STAR data on vSTAR data on v22 of charged of charged hadrons are hadrons are NOTNOT reproduced in the reproduced in the hadronhadron--string picture (UrQMD) =>string picture (UrQMD) =>

evidence forevidence for huge plasma pressure ?! huge plasma pressure ?!

•• PHOBOS data on vPHOBOS data on v22 for charged hadrons for charged hadrons ((all pall pTT) are underestimated in HSD by ) are underestimated in HSD by ~30%~30%

PRC 67 (2003) 054905, Nucl. Phys. A 735 (2004) 277PRC 67 (2003) 054905, Nucl. Phys. A 735 (2004) 277

factor 2factor 2

HSDHSD

UrQMDUrQMD

Elliptic Flow at 62.4 Elliptic Flow at 62.4 and 200 and 200 GeVGeV Au+AuAu+Auv 2

pT [GeV/c]

! "# $

√

stat. error onlysys. error <20%

v 2

pT [GeV/c]

%&'ππππ(" ) *+,,,ππππ )- ."'//

√

stat. error onlysys. error <15%

Collective flow Collective flow -- hydrodynamics hydrodynamics

System behaves like a System behaves like a strongly interacting liquidstrongly interacting liquid (of low viscosity). (of low viscosity).

System is likely to be System is likely to be partonicpartonic, but not ‘plasma, but not ‘plasma--like’ (weakly interacting).like’ (weakly interacting).

In the bulk (low pIn the bulk (low pTT) : ) : hydrodynamics works !hydrodynamics works !(full hydro or blastwave parametrization) (full hydro or blastwave parametrization)

! "##

$ ## # %

&√ ' ' ()) *

+ , !

- . )/)0

0 1 2-0 3

/ 43546

12 ###2 ### 3 4 5, #6#2 #6#2 # ##

Elliptic flow scalingElliptic flow scaling

47E. Bratkovskaya, W. Cassing, V. Konchakovski, O. Linnyk, E. Bratkovskaya, W. Cassing, V. Konchakovski, O. Linnyk, arXivarXiv:1101.5793:1101.5793 [[nuclnucl--thth] ]

The mass splitting at low pT is approximately reproduced as well as the meson-baryon splitting for pT > 2 GeV/c !

The scaling of v2 with the number of constituent quarks nq is roughly in line with the data .

Open and hidden charmOpen and hidden charm

Charm particlesCharm particlesCharm particles

‚Open‘ charm‚Open‘ charm

Mesons:( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )

GeV 1.864m scDscD

scDscD

ucDucD

dcDdcD

ucDucD

dcDdcD

D

*S

*S

SS

0*0*

**

00

=

−+

−+

−+

−+

Baryons:Baryons:( )( )

GeV 2.284m ...udc

udc

C

C

=Λ

+

+

C

‚Hidden‘ charm‚Hidden‘ charm

( )( )( )( )( )

( )( )( )( )

...

2

1

0

41604040

MeV 37292m 3770MeV 3685.92SMeV 3556.21PMeV 3510.51PMeV 3415.01PMeV 3096.81SJ/MeV 2979.81S

D

ΨΨ

=>ΨΨ

Ψ

C

C

C

C

χχχ

η

mesonscc

DD

ee

hadronshadrons cc

:Decays

→Ψ

→ΨΨ+Ψ→Ψ

+→→

−+

)3770(

)'(J/

J/)'( γχγ

Anomalous J/Anomalous J/ΨΨΨΨΨΨΨΨ suppression in A+A suppression in A+A

Hidden charm: J/Hidden charm: J/ΨΨΨΨΨΨΨΨ , , ΨΨΨΨΨΨΨΨ‘:‘: Anomalous J/Anomalous J/ΨΨΨΨΨΨΨΨ suppression in A+A suppression in A+A (NA38/NA50/NA60)(NA38/NA50/NA60)

Heavy flavor sectorHeavy flavor sector reflects the early dynamics since heavy hadrons can reflects the early dynamics since heavy hadrons can onlyonlybe formed in the very early phasebe formed in the very early phase of heavyof heavy--ion collisions !ion collisions !

J/J/ΨΨΨΨΨΨΨΨ ‚normal‘‚normal‘ absorption absorption by nucleons by nucleons (Glauber model) (Glauber model)

Experimental observation:Experimental observation:extra suppression in A+A collisions; extra suppression in A+A collisions; increasing with centralityincreasing with centrality

There should be There should be ‚normal‘ nuclear absorption‚normal‘ nuclear absorption, , i.e. dissociation of charmonium by inelastic i.e. dissociation of charmonium by inelastic interactions with nucleons of the interactions with nucleons of the target/projectiletarget/projectile

CharmoniumCharmonium--N dissociation cross section can N dissociation cross section can be fixed from p+A data be fixed from p+A data

I. Scenarios for charmonium suppression in A+AI. Scenarios for charmonium suppression in A+AI. Scenarios for charmonium suppression in A+A

•• I. QGP threshold meltingI. QGP threshold melting[[Satz Satz et al’03et al’03]:]:Charmonia suppression sets in abruptly at Charmonia suppression sets in abruptly at threshold energy densities, where threshold energy densities, where χχ44 and and 7 57 5ΨΨ are melting are melting

7 '5 &"8"&9,:; < %::

χχχχχχχχC C meltingmeltingJ/J/ΨΨΨΨΨΨΨΨ

•• QGP color screening: QGP color screening: [Matsui and Satz ’86]: [Matsui and Satz ’86]: dissociation of dissociation of

charmonia in the deconfined mediumcharmonia in the deconfined medium: : cc--cbar cannot form a bound state (J/cbar cannot form a bound state (J/ΨΨΨΨΨΨΨΨ) ) due to color screening in QGPdue to color screening in QGP

•• Regeneration of J/Regeneration of J/ΨΨΨΨΨΨΨΨ in QGP at Tin QGP at TCC::[Braun[Braun--Munzinger, Thews, Ko et al. `01]Munzinger, Thews, Ko et al. `01]

J/J/ΨΨΨΨΨΨΨΨ+g +g <<<<<<<<−−−−−−−−>>>>>>>> c+cbar+gc+cbar+g

•• However,However, lattice QCDlattice QCD predicts (2004): predicts (2004): J/J/ΨΨΨΨΨΨΨΨ can exist up to ~2 Tcan exist up to ~2 TCC !!

Quarkonium dissociation temperatures:Quarkonium dissociation temperatures:

II. Scenarios for charmonium suppression in A+AII. Scenarios for charmonium suppression in A+AII. Scenarios for charmonium suppression in A+A

0 20 40 60 80 100 120 1400

10

20

30

40

50

NA50 (2000):anal. Aanal. Banal. C

HSD UrQMD

Bµµµµ µµµµ

σσ σσ(J/

ΨΨ ΨΨ)/ σσ σσ

(DY

)| 2.9-

4.5

Pb+Pb, 160 A GeV

ET [GeV]

•• II. Comover absorptionII. Comover absorption[Gavin & Vogt, Capella et al. 97]:charmonium absorption by low charmonium absorption by low energy inelastic scattering with energy inelastic scattering with ‚comoving‘ mesons‚comoving‘ mesons (m=(m=π,η,ρ,...):π,η,ρ,...):π,η,ρ,...):π,η,ρ,...):π,η,ρ,...):π,η,ρ,...):π,η,ρ,...):π,η,ρ,...):

J/J/ΨΨΨΨΨΨΨΨ+m +m <<<<<<<<−−−−−−−−>>>>>>>> D+DbarD+DbarΨΨΨΨΨΨΨΨ‘+m ‘+m <<<<<<<<−−−−−−−−>>>>>>>> D+DbarD+DbarχχχχχχχχCC+m +m <<<<<<<<−−−−−−−−>>>>>>>> D+DbarD+Dbar

+ + Charmonium recombination by Charmonium recombination by DD--Dbar annihilation:Dbar annihilation:

5 10 15 20

10 -8

10 -7

10 -6

10 -5

10 -4

10 -3

tim e [fm/c]

J/ΨΨΨΨ +m ->D+D bar D +D bar->J/ΨΨΨΨ +m

Pb+Pb, s1/2=17.3 G eV , central

dN/d

t

5 10 15 20

10-4

10-3

10-2

10-1

time [fm/c]

J/ΨΨΨΨ+m->D+Dbar D+Dbar->J/ΨΨΨΨ+m

Au+Au, s1/2=200 GeV, central

dN/d

t

At At SPSSPS recreation of J/recreation of J/ΨΨΨΨΨΨΨΨ by D+Dbar by D+Dbar annihilation is annihilation is negligiblenegligible

but at but at RHICRHIC recreation of J/recreation of J/ΨΨΨΨΨΨΨΨ by by D+Dbar annihilation is D+Dbar annihilation is strongstrong!!

NNDDDD~16~16

I,II. Scenarios for charmonium suppression in A+AI,II. Scenarios for charmonium suppression in A+AI,II. Scenarios for charmonium suppression in A+A

•• QGP threshold melting as well as a comover absorption scenario QGP threshold melting as well as a comover absorption scenario arearequalitativelyqualitatively consistentconsistent with exp. data (for In+In and Pb+Pb) at SPS energies with exp. data (for In+In and Pb+Pb) at SPS energies

•• Increase the energy: Increase the energy: new RHIC data new RHIC data atatss1/21/2=200 GeV for Au+Au=200 GeV for Au+Au: : suppression at forwardsuppression at forward--rapidity is larger then rapidity is larger then at midat mid--rapidities !rapidities !Nuclear modification factor:Nuclear modification factor:

0.0

0.5

1.0

PHENIX, |y|<0.35 PHENIX, 1.2<|y|<2.2

HSD |y|<0.35 1.2<|y|<2.2

RA

A(J

/ ΨΨ ΨΨ)

Au+Au, s1/2=200 GeV, QGP threshold scenario

+ recombinationD+Dbar<−><−><−><−> J/ΨΨΨΨ +m

without recombination

0 100 200 300

0.000

0.005

0.010

0.015

Bµµµµ µµµµ

( ΨΨ ΨΨ')

σσ σσ ΨΨ ΨΨ' /

Bµµµµ µµµµ

(J/ ΨΨ ΨΨ

) σσ σσJ/

ΨΨ ΨΨ

Npart

0 100 200 300 400 N

part

QGP threshold melting scenario is ruled out by QGP threshold melting scenario is ruled out by PHENIX dataPHENIX data!!

J/J/Ψ Ψ Ψ Ψ Ψ Ψ Ψ Ψ and and ΨΨΨΨΨΨΨΨ´ suppression in Au+Au at RHIC: ´ suppression in Au+Au at RHIC: (I.)(I.) QGP threshold melting scenarioQGP threshold melting scenario

Satz’s Satz’s model:model: complete dissociation of complete dissociation of initial initial J/J/Ψ Ψ Ψ Ψ Ψ Ψ Ψ Ψ and and ΨΨΨΨΨΨΨΨ´ due to the huge local due to the huge local energy densities ! energy densities !

CharmoniaCharmonia recombinationrecombination by Dby D--DbarDbar annihilationannihilationis important, however, it can not generate enough is important, however, it can not generate enough charmoniacharmonia, especially for peripheral collisions! , especially for peripheral collisions!

[Olena Linnyk et al.,[Olena Linnyk et al.,arXivarXiv:070:0705.4443, 5.4443, PRC 76 (2007) 041901 PRC 76 (2007) 041901 ]]

0.0

0.5

1.0 PHENIX, |y|<0.35 PHENIX, 1.2<|y|<2.2

Au+Au, s1/2=200 GeV,comover absorption

HSD |y|<0.35 1.2<|y|<2.2

RA

A(J

/ ΨΨ ΨΨ)

0 100 200 300 400

0.000

0.005

0.010

0.015

D+Dbar<−><−><−><−> J/ΨΨΨΨ +m

Bµµµµ µµµµ

( ΨΨ ΨΨ')

σσ σσ ΨΨ ΨΨ' /

Bµµµµ µµµµ

(J/ ΨΨ ΨΨ

) σσ σσJ/

ΨΨ ΨΨ

Npart

J/J/Ψ Ψ Ψ Ψ Ψ Ψ Ψ Ψ and and ΨΨΨΨΨΨΨΨ´ suppression in Au+Au at RHIC: ´ suppression in Au+Au at RHIC: (II.) Comover absorption (+ recombination by D(II.) Comover absorption (+ recombination by D--Dbar annihilation)Dbar annihilation)

In the comover scenario the J/In the comover scenario the J/Ψ Ψ Ψ Ψ Ψ Ψ Ψ Ψ suppression at suppression at midmid--rapidityrapidity is is strongerstrongerthanthan at at forwardforward rapidity, rapidity, unlike the data!unlike the data!

Pure comover scenario is ruled out by Pure comover scenario is ruled out by PHENIX dataPHENIX data!!

-3 -2 -1 0 1 2 3

10-4-3 -2 -1 0 1 2 3

10-4

central, 0-20%

Bµµµµ µµµµ

dN

(J/ ΨΨ ΨΨ

)/dy

-3 -2 -1 0 1 2 310-5

10-4

comover PHENIX

Au+Au, s1/2=200 GeV

HSD

semi-central, 20-40%

semi-peripheral, 40-60%

Bµµµµ µµµµ

dN

(J/ ΨΨ ΨΨ

)/dy

y-3 -2 -1 0 1 2 3

10-6

10-5

y

peripheral, 60-90%

Olena Linnyk et al., Olena Linnyk et al., nuclnucl--th/0612049, NPA 786 (2007) 183; th/0612049, NPA 786 (2007) 183; arXivarXiv::0801.4282, NPA 807 (2008) 79 0801.4282, NPA 807 (2008) 79

J/J/Ψ Ψ Ψ Ψ Ψ Ψ Ψ Ψ and and ΨΨΨΨΨΨΨΨ´ suppression in Au+Au at RHIC: ´ suppression in Au+Au at RHIC: (III.) Pre(III.) Pre--hadronic interaction scenariohadronic interaction scenario

In the prehadronic interaction scenario the J/In the prehadronic interaction scenario the J/Ψ Ψ Ψ Ψ Ψ Ψ Ψ Ψ rapidityrapidity distributiondistribution has the right has the right shape shape like the PHENIX data! => like the PHENIX data! => can can describe the describe the RHIC RHIC datadata atat ss1/21/2=200=200GeVGeV for Au+Aufor Au+Au at at midmid-- and forwardand forward--rapidities simultaneouslyrapidities simultaneously..

Olena Linnyk et al., Olena Linnyk et al., arXivarXiv::0801.4282, NPA 807 (2008) 79 0801.4282, NPA 807 (2008) 79

-3 -2 -1 0 1 2 3

10-4-3 -2 -1 0 1 2 3

10-4

central, 0-20%

Bµµµµ µµµµ

dN

(J/ ΨΨ ΨΨ

)/dy

-3 -2 -1 0 1 2 310-5

10-4

comover prehadron interactions PHENIX

Au+Au, s1/2=200 GeV

HSD

semi-central, 20-40%

semi-peripheral, 40-60%

Bµµµµ µµµµ

dN

(J/ ΨΨ ΨΨ

)/dy

y-3 -2 -1 0 1 2 3

10-6

10-5

y

peripheral, 60-90%0 100 200 300 4000.0

0.5

1.0

Au+Au, s1/2=200 GeVPrehadron interactions

PHENIX |y|<0.35 1.2<|y|<2.2

Npart

HSD |y|<0.35 1.2<|y|<2.2

RA

A(J

/ ΨΨ ΨΨ)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5-0.05

0.00

0.05

0.10

0.15

0.20Au+Au, s1/2=200 GeV

b=7 fm, 0<y<1

v 2 (pT)

PHENIX D+Dbar J/ΨΨΨΨ

pT [GeV/c]

HSD: v2 of D+Dbar and J/ΨΨΨΨ from Au+Au versus pT and y at RHICHSD: vHSD: v22 of D+Dbar and J/of D+Dbar and J/ΨΨΨΨΨΨΨΨ from Au+Au versus pfrom Au+Au versus pTT and y at RHICand y at RHIC

HSD:HSD: DD--mesons and J/mesons and J/Ψ Ψ Ψ Ψ Ψ Ψ Ψ Ψ follow the follow the charged particle flow charged particle flow =>=>=>=>=>=>=>=> small vsmall v2 2 < 3%< 3%

•• STAR data STAR data show very show very large large collective collective flow of Dflow of D--mesons mesons vv22~15%!~15%!

=> strong initial flow of => strong initial flow of nonnon--hadronic nature!hadronic nature!

-6 -4 -2 0 2 4 60.00

0.01

0.02

0.03

0.04

0.05

0.06

PHOBOS HSD

Au+Au, s1/2=200 GeVcharge particles

v 2( ηη ηη)

ηηηη -2 -1 0 1 2

-0.02

0.00

0.02

0.04

0.06Au+Au, s1/2=200 GeV

b=7 fm

v 2 (y)

D+Dbar J/ΨΨΨΨ

y

Collective flow Collective flow from from hadronic hadronic interactionsinteractions is is too low at too low at midrapidity !midrapidity !

PRC 71 (2005) 044901PRC 71 (2005) 044901

D/DbarD/Dbar--mesons: inmesons: in--medium effectsmedium effects

•• Dropping DDropping D--meson massesmeson masses with with increasing light quark density increasing light quark density might give a might give a large enhancement of large enhancement of the open charm yieldthe open charm yield at 25 A GeV ! at 25 A GeV !

FAIR (CBM)FAIR (CBM)

•• Charmonium suppression increasesCharmonium suppression increasesfor dropping Dfor dropping D--meson masses! meson masses!

2.0 2.5 3.0 3.510-8

10-6

10-4

10-2 __D+D

bare in-medium(2

mT)

-1dN

/dm

T [G

eV-2]

Au+Au, 25 A GeV, central

mT [GeV]

Ch. SU(4):Ch. SU(4): A. Mishra et al., PRC69 (2004) 015202A. Mishra et al., PRC69 (2004) 015202QCD sum rule:QCD sum rule: Hayashigaki, PLB487 (2000) 96Hayashigaki, PLB487 (2000) 96Coupled channel:Coupled channel: Tolos et al., EPJ C43 (2005) 761Tolos et al., EPJ C43 (2005) 761 HSD: NPA691 (2001) 761HSD: NPA691 (2001) 761

HSDHSD

0 1 2 3 41300

1400

1500

1600

1700

1800

QCD sum rule

Coupledchannel

Ch. SU(4) model: MFT RHA

D++++

D−−−−

mD

−− −− [M

eV]

ρρρρB/ρρρρ0

0 1 2 3 41300

1400

1500

1600

1700

1800

1900

QCD sum rule

Ch. SU(4) model: MFT RHA

mD

+ [M

eV]

∆ ∆ ∆ ∆ ∆ ∆ ∆ ∆ mmD D ((ρρρρρρρρ)= )= -- 50 (MeV) 50 (MeV) ρρρρρρρρ//ρρρρρρρρ00

Jet quenching and angular correlations Jet quenching and angular correlations in A+Ain A+A

What is a jet?

c

chbbaa

abcdba

T

hpp

zD

cdabtd

dQxfQxfdxdxK

pdyd

d

πσσ 0

/222 )(

ˆ),(),( →=

!"#$ %&'

Discovery of “Jet Quenching”Discovery of “Jet Quenching”Discovery of “Jet Quenching”

2 2/AA bin pp

AAT T

d N dR

dyd p dyd pσ σ=

0

1

2

AAR

pT

Behavior of hard probesBehavior of hard probes

‘jet quenching’ ‘jet quenching’ –– inelastic and elastic scattering of the partons in inelastic and elastic scattering of the partons in the medium (partonic and hadronic)the medium (partonic and hadronic)

Dynamics andDynamics and hadronizationhadronization mmechanismsechanisms

ησηddpdT

ddpNdpR

TNN

AA

TAA

TAA //

)( 2

2

=

<<NNbinarybinary>/>/σσσσσσσσinelinelpp+p+p

nucleonnucleon--nucleonnucleoncross sectioncross section

1. Compare Au+Au to nucleon1. Compare Au+Au to nucleon--nucleon cross sectionsnucleon cross sections2. Compare Au+Au central/peripheral 2. Compare Au+Au central/peripheral

Nuclear Nuclear Modification Modification Factor:Factor:

If If no “effects”:no “effects”:RRAAAA < 1 in regime of soft physics< 1 in regime of soft physics

(since soft physics scales with N(since soft physics scales with Npartpart

which is smaller then Nwhich is smaller then Nbinarybinary))RRAAAA = 1 at high= 1 at high--ppTT where hard where hard

scattering dominatesscattering dominatesSuppression:Suppression:RRAAAA < 1 at high< 1 at high--ppT T “jet quenching”“jet quenching”Also: Also: RRAAAA > 1 : Cronin Effect> 1 : Cronin Effect

AA

AA

AA

Nuclear Modification FactorNuclear Modification Factor

“Cronin effect”“Cronin effect”Initial state multiple scatteringInitial state multiple scatteringleading to Cronin enhancement (Rleading to Cronin enhancement (RAAAA>1) >1)

JetJet--quenchingquenching(R(RAAAA<<1) 1)

AA

AA

AA

Nuclear Modification FactorNuclear Modification Factor

•• HighHigh ppTT enhancementenhancement in in d+Au collisions at d+Au collisions at √√ssNNNN=200=200 GeVGeV

•• Comparing Au+Au to Comparing Au+Au to d+Au atd+Au at midrapiditymidrapidity Strong effect of dense Strong effect of dense mediummedium PartonicPartonic energy lossenergy loss??

charged hadrons

Centrality DependenceCentrality Dependence

•• Dramatically different and opposite centrality evolution of Au+ADramatically different and opposite centrality evolution of Au+Au u experiment from d+Au control experiment.experiment from d+Au control experiment.

•• Jet suppression is clearly a final state effect of the dense medJet suppression is clearly a final state effect of the dense medium! ium!

Au + Au Experiment d + Au Control Experiment

Preliminary DataFinal Data

Cronin effect at RHIC (HSD)Cronin effect at RHIC (HSD)

Cronin effect:Cronin effect: initial state initial state semisemi--hard gluon radiationhard gluon radiation increases increases ppTT spectra already in p+A or d+Aspectra already in p+A or d+A

Tppinelasppcoll

TdA2event

dATdA /dydpd/N

/dydpNd1/N)(pR⋅><

⋅=

W. Cassing, K. Gallmeister and C. Greiner, W. Cassing, K. Gallmeister and C. Greiner, Nucl. Phys. A 735 (2004) 277Nucl. Phys. A 735 (2004) 277

Modelling of the Cronin effect Modelling of the Cronin effect in HSD:in HSD:

<k<kTT22>>AAAA = <k= <kTT

22>>PPPP (1+a N(1+a NPrevPrev))

NNPrevPrev= number of previous = number of previous collisionscollisions

parameter a = 0.25 parameter a = 0.25 –– 0.40.4 7 - &5%22

7 - &%22

High pHigh pTT suppression in nonsuppression in non--central Au+Au (HSD)central Au+Au (HSD)

7 - &%22

Cronin effect on Cronin effect on ππππππππ, K, K++ mmTT--spectra in A+A (HSD)spectra in A+A (HSD)

•• Very small effect at Very small effect at AGSAGS

•• Hardening of the mHardening of the mTTspectra at top SPSspectra at top SPS

•• Substantial Substantial hardening of the mhardening of the mT T spectra at RHIC spectra at RHIC ––> > large improvement ! large improvement !

•• Consistent with other Consistent with other observables !observables !

0.0 0.5 1.0 1.5 2.0 2.5

10-1

100

101

102

103

mT-1

dN

/(dm

Tdy) [

(GeV

)-2]

mT-1

dN

/(dm

Tdy) [

(GeV

)-2]

K −−−−*0.1

K +

Au+Au, s1/2=200 GeV, 5%, midrapidityππππ −−−−

mT-1

dN

/(dm

Tdy) [

(GeV

)-2]

0.0 0.2 0.4 0.6 0.8 1.010-2

10-1

100

101

102

103

K −−−−*0.1

K +

Pb+Pb, 160 A GeV, 5%, midrapidityππππ−−−−

0.0 0.2 0.4 0.6 0.8 1.0

10-2

10-1

100

101

102

103

default with Cronin effect

HSD with Cronin effect

K −−−−*0.1

K +

Au+Au, 11 A GeV, 5%, midrapidityππππ−−−−

mT-m0 [GeV]

PRC 69 (2004) 015202PRC 69 (2004) 015202

Different Ways to “Skin a Jet”Different Ways to “Skin a Jet”

1) Integral Distributions:1) Integral Distributions:<<ppTT>, <>, <NNchch>>

2) Single Particle Spectra:2) Single Particle Spectra:ddσσσσσσσσ/dp/dpT T RRAAAA, R, RdAdA

3) 23) 2--Particle Correlations:Particle Correlations:dN/d(dN/d(∆φ∆φ∆φ∆φ∆φ∆φ∆φ∆φ))

4) Jet Reconstruction:4) Jet Reconstruction:ddσσσσσσσσ/dE/dET T , Frag. Func., Frag. Func.

triggertrigger

“Trigger”φφφφ = 0

Adler et al., PRL90:082302 (2003), STAR

near-side

awayaway--sideside

Jet Energy LossJet Energy Loss

High pT particle

p+p

High pT particle

Au+Au

away

nearC

ollim

ated

regi

on

away

QGP suppression ?!QGP suppression ?!

Jet suppression: dN/dJet suppression: dN/dϕϕϕϕϕϕϕϕ (HSD)(HSD)

•• The jet angular The jet angular correlations for correlations for pppp are are fine !fine !

•• The nearThe near--side jet side jet angular correlation for angular correlation for central Au+Au is well central Au+Au is well described, but the described, but the suppression of the farsuppression of the far--side jet is too low side jet is too low !!

= > *

7

(pre(pre--)hadronic FSI)hadronic FSI

QGP suppressionQGP suppression

!"# !"#

The QGP is observed at RHIC !The QGP is observed at RHIC !

The phase diagram of QCDThe phase diagram of QCD

0 200 400 600 800 1000 12000

50

100

150

200

250endpoint(2+1 flavor lattice QCD)[Fodor, Katz '04]

phase boundary

chemical freezout [Cleymans et al.]

endpoint (3 flavor lattice QCD)[Karsch et al., QM'04]

endpoint(2+1 flavor lattice QCD)[Fodor, Katz '02]

UrQMD: Au+Au, 11 A GeV Pb+Pb, 40 A GeV Pb+Pb, 160 A GeV Au+Au, 21300 A GeV

µµµµB [MeV]

T [M

eV]

UrQMD initial energy UrQMD initial energy density is density is higherhigher than the than the boundary from LQCDboundary from LQCD

••TriTri--critical point reached critical point reached somewhere between 20 somewhere between 20 and 30 A GeVand 30 A GeV

•• we are probing awe are probing a new new phase of matter phase of matter already atalready atAGS! AGS!

OutlookOutlook

The QuarkThe Quark--GluonGluon--Plasma is there!Plasma is there!But what are the But what are the properties properties of this of this phase ?!phase ?!

Initial idea (1970 Initial idea (1970 –– 2003):2003):QGP is a weakly interacting QGP is a weakly interacting gas of colored but almost massless gas of colored but almost massless quarks and gluonsquarks and gluons

State of the art 2010:State of the art 2010:QGP is a strongly interacting QGP is a strongly interacting and almost ideal and almost ideal „„color liquidcolor liquid““ !!

New phase diagram of QCDNew phase diagram of QCD

A. Peshier, W. Cassing, PRL (2005) A. Peshier, W. Cassing, PRL (2005) 0 200 400 600 800 1000

10

100

1000

nonperturbative colored parton gas

colored parton liquid

endpoint[Fodor, Katz '04]

chemical freezout [Cleymans et al.]

UrQMD: Au+Au, 11 A GeV Pb+Pb, 40 A GeV Pb+Pb, 160 A GeV Au+Au, 21300 A GeV

µµµµB [MeV]

T [M

eV]

THE ENDTHE END