Charmonium dynamics in heavy ion collisions Olena Linnyk 28 June 2007

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

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´

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:0704.1410

Charmonium production Hard probe -> binary scaling!

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

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!

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)

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 !? =

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/0310354 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)

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/0310354 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)

Comparison to data

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) 054903, OL et al NPA786 (2007) 183]

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

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:0705.4443]

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

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 ?

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

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 In+In @ 158 A GeV, while Y´ 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).

E. Bratkovskaya, W. Cassing, H. Stöcker Thank you! arXiv:0705.4443 nucl-th/0612049 arXiv:0704.1410

Back-up slide 1 FAIR predictions

Back-up slide 2 Energy density

Back-up slide 3 Rapidity