1. Charmonium dynamics in heavy ion collisions
Olena Linnyk
28 June 2007

2. Charmonium production vs absorption
Dbar
J/Y cC Y‘
Hadronization
Initial State
time
Freeze-out
Quark-Gluon-Plasma ?
Transport models
Microscopical transport models provide the dynamical description of nonequilibrium effects in heavy-ion collisions

3. Basic concepts of Hadron-String Dynamics
for each particle species i (i = N, R, Y, p, r, 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->X, mB->X, X =many particles)
Implementation of detailed balance on the level of 1<->2 and 2<->2 reactions (+ 2<->n multi-meson fusion reactions)
Off-shell dynamics for short living states
BB <-> B´B´, BB <-> B´B´m, mB <-> m´B´, mB <-> B´

4. Degrees of freedom in HSD
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 :
no explicit parton-parton interactions (i.e. between quarks and gluons) outside strings!
no QCD EoS for partonic phase
under construction: PHSD – Parton-Hadron-String-Dynamics W. Cassing arXiv:

5. Charmonium production
Hard probe -> binary scaling!

6. Charmonium production in pN
sJ/Yexp = sJ/Y + B(cc->J/Y) scc + B(Y‘->J/Y) sY‘

7. Regeneration
At SPS recreation of J/Y by D-Dbar annihilation is negligible
But at RHIC recreation of J/Y by D-Dbar annihilation is strong!

8. 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)

9. Anomalous absorption of J/Y in very central Pb+Pb
Normal absorption
NA50 (QM2002):
Anomalous absorption of J/Y in very central Pb+Pb
Discovery of QGP !? =

10. 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=p,h,r,...)
J/Y+m -> D+Dbar
Y´ +m -> D+Dbar
cC +m -> D+Dbar
Digal, Fortunato, Satz
hep-ph/
J/Y
cC melting
but (!)
Lattice QCD predicts (2004): J/Y can exist up to ~2 TC !
Regeneration of J/Y in QGP at TC [Braun-Munzinger, Thews, Ko et al. `01] J/Y+g <-> c+cbar+g
but (!)
Comover density and meson absorption cross sections unknown
Regeneration (D+Dbar->J/Y+m)

11. Scenarios for anomalous charmonium suppression
in HSD
QGP colour screening
[Matsui and Satz ’86]
Threshold melting
= geometrical Glauber model [Blaizot et al.]
Charmonia suppression sets in abruptly at threshold energy densities, where
cc is melting,
Y´ is melting,
J/Y is melting
Lattice QCD:
e(cc) =2 GeV/fm3
e(Y´) =2 GeV/fm3
e(J/Y)=16 GeV/fm3
Comover absorption
Phase-space model for cc+meson dissociation
Inverse cross sections by detailed balance!
Comover absorption
[Gavin & Vogt, Capella et al.`97]:
charmonium absorption by low energy inelastic scattering with ‚comoving‘ mesons (m=p,h,r,...)
J/Y+m -> D+Dbar
Y´ +m -> D+Dbar
cC +m -> D+Dbar
Digal, Fortunato, Satz
hep-ph/
J/Y
cC melting
but (!)
Lattice QCD predicts (2004): J/Y can exist up to ~2 TC !
Regeneration of J/Y in QGP at TC [Braun-Munzinger, Thews, Ko et al. `01] J/Y+g <-> c+cbar+g
but (!)
Comover density and meson absorption cross sections unknown
Regeneration (D+Dbar->J/Y+m)

12. Comparison to data

13. Pb+Pb and In+In @ 158 A GeV J/Y
In+In consistent both with threshold melting and comover absorption scenarios; Pb+Pb indicates importance of comover interaction
[E.L.Bratkovskaya et al PRC69 (2004) , OL et al NPA786 (2007) 183]

14. Pb+Pb and In+In @ 158 A GeV Y´
Y´ data contradict threshold melting scenario with lQCD ed

15. Au+Au @ s1/2=200 GeV Comover absorption
In comover scenario, suppression at mid-y stronger than at forward y, unlike data
Space for parton phase effects
[OL et al arXiv: ]

16. Au+Au @ s1/2=200 GeV Threshold melting
Neither of the two scenarios describes PHENIX data

17. J/Y excitation function
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/Y melting scenario with hadronic comover recreation shows a maximum suppression at Ebeam = 1 A TeV; exp. data ?

18. Y´ excitation function
preliminary
Y´ excitation function e e
Y´ suppression provides independent information on absorption vs. recreation mechanisms !

19. Summary
J/Y probes early stages of fireball and HSD is the tool to model it.
Comover absorption and threshold melting both reproduce J/Y survival in Pb+Pb as well as in 158 A GeV, while Y´ data favour comover absorption.
Neither hadronic interactions nor colour screening satisfactory describes the 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).

20. E. Bratkovskaya, W. Cassing, H. Stöcker
Thank you!
arXiv:
nucl-th/
arXiv:

21. Back-up slide 1 FAIR predictions

22. Back-up slide 2 Energy density

23. Back-up slide 3 Rapidity