Olena LinnykOlena Linnyk

Charmonium dynamics in heavy ion collisions

28 June 2007

Microscopical transport models provide the dynamical Microscopical transport models provide the dynamical description of description of nonequilibriumnonequilibrium effects in heavy-ion collisions effects in heavy-ion collisions

Transport modelsTransport models

Quark-Gluon-Plasma ?

time

DD

DDbarbar

J/J/

CC

‘‘

Charmonium production vs absorption

Initial StateHadronization

Freeze-out

Basic concepts of Hadron-String Dynamics

• for each particle species i (i = N, R, Y, , , K, …) the phase-space density fi

follows the transport equations

with the collision terms Icoll describing: elastic and inelastic hadronic reactions formation and decay of baryonic and mesonic resonances string formation and decay (for inclusive production: BB(for inclusive production: BBXX, mB, mBXX, , XX =many particles) =many particles)

• Implementation of detailed balance on the level of 12 and 22 reactions (+ 2n multi-meson fusion reactions)

• Off-shell dynamics for short living states

BB BB B´B´, BB B´B´, BB B´B´m, mB B´B´m, mB m´B´, mB m´B´, mB BB´́

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

• hadrons - baryons and mesons including excited states (resonances)

• strings – excited colour singlet states (qq - q) or (q – qbar)

Based on the LUND string model

& perturbative QCD via PYTHIA

• leading quarks (q, qbar) & diquarks

(q-q, qbar-qbar)

NOT included in the transport models presented here :o no explicit parton-parton interactions (i.e. between quarks and gluons) outside

strings!o no QCD EoS for partonic phase under construction: PHSD – Parton-Hadron-String-Dynamics W. Cassing arXiv:0704.1410

Degrees of freedom in HSD

pre-hadronspre-hadrons

F

__

qqq

time

color electricfield

z

Charmonium production

Hard probe binary scaling!

Charmonium production in pN

J/J/expexp = = J/J/ + + BB((cc->J/->J/)) cc + + BB((‘‘->J/->J/) ) ‘‘

1 0 1 001 0-1

1 00

1 01

1 02

1 03

1 04

1 05

1 06

1 07

J /

/

p + N D + D b a r

(s)

[nb]

s1 /2 [G eV ]-4 -2 0 2 4

0

20

40

60

PHENIX HSD scaled with cross section ratio

pp->J/+X, s1/2=200 GeV

Br

d/d

y [n

b]

Regeneration

5 10 15 20

10-8

10-7

10-6

10-5

10-4

10-3

time [fm/c]

J/+m->D+Dbar D+Dbar->J/+m

Pb+Pb, s1/2=17.3 GeV, central

dN

/dt

At SPS recreation of J/At SPS recreation of J/ by D-Dbar annihilation is negligible by D-Dbar annihilation is negligible

5 10 15 20

10-4

10-3

10-2

10-1

time [fm/c]

J/+m->D+Dbar D+Dbar->J/+m

Au+Au, s1/2

=200 GeV, central

dN

/dt

But at RHIC recreation of J/But at RHIC recreation of J/ by D-Dbar annihilation is by D-Dbar annihilation is strong!strong!

Charmonium absorption

Charmonium is absorbed by :

Scattering on nucleons (normal nuclear absorption, as in pA) Interaction with secondary hadrons (comovers) Dissociation in the deconfined medium (suppression in QGP)

Normal absorption

0 50 100 150 2000 100 200 300 4000

10

20

30

40

HSD

In+In, 158 A GeV

Npart

Baryon absorption Glauber model NA60 2005. HSD

Pb+Pb, 158 A GeV

Npart

Baryon absorption Glauber model NA50 2004

NA50 (QM2002):NA50 (QM2002):AnomalousAnomalous absorption of J/Y in very central Pb+Pb absorption of J/Y in very central Pb+Pb

Discovery of QGP !?Discovery of QGP !?

Scenarios for anomalous charmonium suppression

• QGP colour screening

[Matsui and Satz ’86]• Comover absorption[Gavin & Vogt, Capella et al.`97]:

charmonium absorption by low energy inelastic scattering with ‚comoving‘ mesons (m=

J/+m D+Dbar

´ +m D+Dbar

C +m D+Dbar

Digal, Fortunato, Satzhep-ph/0310354

J/C melting

but (!) Comover density and meson

absorption cross sections unknown Regeneration (D+DbarJ/+m)

but (!) Lattice QCD predicts (2004): J/ can

exist up to ~2 TC !

Regeneration of J/ in QGP at TC [Braun-Munzinger, Thews, Ko et al. `01]J/+g c+cbar+g

but (!) Comover density and meson

absorption cross sections unknown Regeneration (D+DbarJ/+m)

but (!) Lattice QCD predicts (2004): J/ can

exist up to ~2 TC !

Regeneration of J/ in QGP at TC [Braun-Munzinger, Thews, Ko et al. `01]J/+g c+cbar+g

Scenarios for anomalous charmonium suppression

• QGP colour screening

[Matsui and Satz ’86]• Comover absorption[Gavin & Vogt, Capella et al.`97]:

charmonium absorption by low energy inelastic scattering with ‚comoving‘ mesons (m=

J/+m D+Dbar

´ +m D+Dbar

C +m D+Dbar

Digal, Fortunato, Satzhep-ph/0310354

J/C melting

in HSDThreshold meltingThreshold melting

= geometrical Glauber model [Blaizot et al.]

Charmonia suppression sets in abruptly at threshold energy densities, where

c is melting,´ is melting,J/ is melting

Lattice QCD:(c) =2 GeV/fm3

(´) =2 GeV/fm3

(J/)=16 GeV/fm3

Comover absorptionComover absorption Phase-space model for cc+meson dissociation

4.0 4.5 5.0 5.510

-1

100

101

J/+K*

J/+K

J/+

J/+

[m

b]

s1/2

[GeV]

4 .0 4 .5 5 .0 5 .5100

101

D*+ D b a r*

D + D b a r*, D*+ D b a r

D + D b a r

[m

b]

s1 /2 [G eV ]

Inverse cross sections by detailed balance!Inverse cross sections by detailed balance!

Comparison to data

In+In consistent both with threshold meltingthreshold melting and comover absorptioncomover absorption scenarios; Pb+Pb indicates importance of comovercomover interaction

[E.L.Bratkovskaya et al PRC69 (2004) 054903, OL et al NPA786 (2007) 183]

Pb+Pb and In+In @ 158 A GeV J/J/

0 50 100 150 200 250 300 350 4000.4

0.6

0.8

1.0

1.2

HSD

NA60, In+In, 158 A GeV Comover absorption NA50, Pb+Pb, 158 A GeV Comover absorption

((J

/)/(

DY

)) /

((J

/)/(

DY

))G

laub

er

Npart

0 50 100 150 200 250 300 350 4000.4

0.6

0.8

1.0

1.2

HSD

NA60, In+In, 158 A GeV QGP threshold melting NA50, Pb+Pb, 158 A GeV QGP threshold melting

((J

/)/(

DY

)) /

((J

/)/(

DY

))G

laub

er

Npart

Pb+Pb and In+In @ 158 A GeV´́

0 25 50 75 100 125 1500.000

0.005

0.010

0.015 NA50 1997 NA50 1998-2000 Comover absorption QGP threshold melting:

J/=16,

c

=2, '=2 GeV/fm3

J/=16,

c

=2, '=6.55 GeV/fm3

B

(')

' /

B

(J/

) J/

Pb+Pb, 158 A GeV

HSD

ET [GeV]

´ data contradict threshold melting scenario with lQCD d

Au+Au @ s1/2=200 GeV Comover absorptionComover absorption

[OL et al arXiv:0705.4443]

In comover scenario, suppression atmid-y stronger than atforward y,unlike data

0.0

0.5

1.0

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

RA

A(J

/)

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

Au+Au, s=200 GeV, comover absorption

0 100 200 300

0.000

0.005

0.010

0.015

D+Dbar J/ +m

B

(')

'

/ B

(J

/) J/

Npart

0 100 200 300

D+Dbar J/ +m

+ cut

=1 GeV/fm3

Npart

Space for parton phase effects

Neither of the two scenarios describes PHENIX data

0.0

0.5

1.0

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

R

AA(J

/)

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

+ recombinationD+Dbar J/ +m

without recombination

0.0

0.5

1.0

+ recombinationD+Dbar J/ +m

+ cut

=1 GeV/fm3

Au+Au, s=200 GeV, QGP threshold scenario

0 100 200 300

0.000

0.005

0.010

0.015

B

(')

'

/ B

(J

/) J/

Npart

0 100 200 300

Npart

0 100 200 300 400

0.000

0.005

0.010

0.015

Npart

Au+Au @ s1/2=200 GeV Threshold meltingThreshold melting

J/J/ excitation function

100 1000 100000.0

0.2

0.4

0.6

0.8

1.0

Central

S

Ebeam

, A GeV

Comover + Ecut

Comover

QGP + Ecut

QGP

100 1000 100000.0

0.2

0.4

0.6

0.8

1.0

Minimal bias

HSD

J/ excitation function

SE

beam, A GeV

Comover reactions in the hadronic phase give almost a constant suppression;

pre-hadronic reactions lead to a larger recreation of charmonia with Ebeam .The J/ melting scenario with hadronic comover recreation shows a maximum

suppression at Ebeam = 1 A TeV; exp. data ? exp. data ?

´́ excitation function

100 1000 100000.000

0.004

0.008

0.012

Central

B

(

')

' /

B

(J/

) J/

Ebeam

, A GeV

Comover+Ecut

Comover

QGP+Ecut

QGP

100 1000 10000

Minimal bias

HSD

' to J/ ratio

Ebeam

, A GeV

´ suppression provides independent information on absorption vs. recreation mechanisms !

J/ probes early stages of fireball and HSD is the tool to model it.

Comover absorption and threshold melting both reproduce J/ survival in Pb+Pb as well as in In+In @ 158 A GeV, while ´ data favour comover absorption.

Neither hadronic interactions nor colour screening satisfactory describes the data @ s1/2=200 GeV for Au+Au.

Deconfined phase is clearly reached at RHIC, but a theory having the relevant/proper degrees of freedom in this regime is needed to study its properties (PHSD).

arXiv:0705.4443 arXiv:0704.1410 nucl-th/0612049

Back-up slide 1 FAIR predictions

0 50 100 150 200 250 300 350 4000.0

0.2

0.4

0.6

0.8

1.0

HSD

S(J/)

Npart

Baryon absorption Comover absorption QGP threshold melting

J/=16,

c

=2, '=6.55 GeV/fm3

0 50 100 150 200 250 300 350 4000.000

0.002

0.004

0.006

Au+Au, 25 A GeV

HSD

Comover absorption QGP threshold melting

J/=16,

c

=2, '=6.55 GeV/fm3

QGP threshold melting

J/=16,

c

=2, '=2 GeV/fm3

B

(')

' /

B

(J/

) J/

Npart

Back-up slide 2 Energy density

Back-up slide 3 Rapidity

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

10-4

10-3

threshold melting +energy cut comover absorption +energy cut

QGP no cut comover no cut

PHENIXHSD central

B

dN

(J/

)/d

y

y

Au+Au, s=200 GeV