Olena Linnyk Charmonium in heavy ion collisions 16 July 2007

Anomalous J/  suppression Charm sector reflects the dynamics in the early phase of heavy-ion collisions ! J/  ‚normal‘ absorption by nucleons (Glauber model) Experimental observation (NA38/50/60): extra suppression in A+A collisions; increasing with centrality

Scenarios for anomalous charmonium suppression QGP colour screening [Digal, Fortunato, Satz ’03] Comover absorption [Gavin & Vogt, Capella et al.`97] absorption by low energy inelastic scattering with ‚comoving‘ mesons (m= , , ,...) J/   C melting J/  +m D+Dbar  ´ +m D+Dbar  C +m D+Dbar Dissociation energy density  d ~ 2(T d /T c ) 4 Quarkonium dissociation T:

Microscopical transport models provide the dynamical description of nonequilibrium effects in heavy-ion collisions Transport models Quark-Gluon-Plasma ? time D D bar J/  CCCC ‘‘‘‘ Check the scenarios using transport models Initial State Hadronization Freeze-out HSD – Hadron-String-Dynamics transport approach

Charmonium production in pN  J/  exp =  J/  + B(  c -> J/  )   c + B(  ´ ->J/  )   ´ Hard probe -> binary scaling!

Phase-space model for charmonium + meson dissociation: [PRC 67 (2003) ] 2. J /  recombination cross sections by D+Dbar annihilation: D+Dbar -> J /  (  c,  ‘) + meson ( , K, K*) are determined by detailed balance! constant matrix element 1. Charmonia dissociation cross sections with , K and K* mesons J /  (  c,  ‘) + meson ( , K, K*) D+Dbar comover Modelling the comover scenario in HSD

[Olena Linnyk et al., nucl-th/ , NPA 786 (2007) 183 ] Threshold energy densities: J  melting:  (J  )=16 GeV/fm 3  c melting:  (  c ) =2 GeV/fm 3  ‚  melting:  (  ‚ ) =2 GeV/fm 3 Energy density  (x=0,y=0,z;t) from HSD QGP melting Modeling the QGP melting in HSD

Charmonium recombination by DDbar annihilation At SPS recreation of J/  by D-Dbar annihilation is negligible But at RHIC recreation of J/  by D-Dbar annihilation is strong! N DD ~16

Comparison to data

comover absorption Pb+Pb and 158 A GeV comover absorption [OL et al NPA786 (2007) 183] Pb+Pb and 160 A GeV consistent with the comover absorption for the same parameter set!

threshold melting Pb+Pb and 158 A GeV QGP threshold melting Y ´ absorption too strong, which contradict data [OL et al NPA786 (2007) 183]  (J  )=16 GeV/fm 3,  (  c ) =  (  ‚ ) =2 GeV/fm 3

Comover absorption s 1/2 =200 GeV Comover absorption [OL et al arXiv: ] Space for partonic effects In the comover scenario the J/  suppression at mid- rapidity is stronger than at forward rapidity, unlike the data! Energy density cut  cut =1 GeV/fm 3 reduces the meson comover absorption ||

Threshold melting s 1/2 =200 GeV Threshold melting Satz’s model: complete dissociation of initial J/  and  ´ due to the very large local energy densities ! Charmonia recombination is important! Energy density cut  cut =1 GeV/fm 3 reduces the meson comover absorption, however, D+Dbar annihilation can not generate enough charmonia, especially for peripheral collisions! QGP threshold melting scenario is ruled out by PHENIX data!

J/ Y 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 E beam. exp. data ? The J/  melting scenario with hadronic comover recreation shows a maximum suppression at E beam = 1 A TeV; exp. data ?

Y ´ Y ´ excitation function  ´ 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 158 A GeV, while  ´ data are in conflict with the melting scenario.  Comover absorption and colour screening fail to describe Au+Au at s 1/2 =200 GeV at mid- and forward rapidities simultaneously.  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). PHSD - transport description of the partonic and hadronic phases

arXiv: arXiv: nucl-th/

vs Back-up slide 1 local energy density vs Bjorken energy density transient time for central Au+Au at 200 GeV: t r ~ 2R A /  cm ~ 0.13 fm/c transient time for central Au+Au at 200 GeV: t r ~ 2R A /  cm ~ 0.13 fm/c cc formation time:  C ~ 1/M T ~ 1/4GeV ~ 0.05 fm/c < t r cc formation time:  C ~ 1/M T ~ 1/4GeV ~ 0.05 fm/c < t r cc pairs are produced in the initial NN collisions in time period t r cc pairs are produced in the initial NN collisions in time period t r Bjorken energy density: J  cccc  ‚ ‚ ‚ ‚ at RHIC  Bj  ~ 5 GeV/fm 2 /c A  is the nuclei transverse overlap area  is the formation time of the medium ‚Local‘ energy density  during transient time t r   GeV/fm 2 /c] / [0.13 fm/c] ~ 30 GeV/fm 3 ~ 30 GeV/fm 3 accounting  C :   ~ 28 GeV/fm 3 HSD reproduces PHENIX data for Bjorken energy density very well HSD reproduces PHENIX data for Bjorken energy density very well HSD results are consistent with simple estimates for the energy density HSD results are consistent with simple estimates for the energy density

Back-up slide 2 PHSD Initial A+A collisions – HSD: string formation and decay to pre-hadrons Fragmentation of pre-hadrons into quarks: Dynamical QuasiParticle Model ( Fragmentation of pre-hadrons into quarks: using the quark spectral functions from the Dynamical QuasiParticle Model (DQPM) approximation to QCD Partonic phase: quarks and gluons (= ‚dynamical quasiparticles‘) with off-shell spectral functions (width, mass) defined by DQPM elastic and inelastic parton-parton interactions: elastic and inelastic parton-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: based on DQPM - massive, off-shell quarks and gluons with broad spectral functions hadronize to off-shell mesons and baryons: gluons  q + qbar; q + qbar  meson; q + q +q  baryon gluons  q + qbar; q + qbar  meson; q + q +q  baryon Hadronic phase: hadron-string interactions – off-shell HSD DQPM: Peshier, Cassing, PRL 94 (2005) ; DQPM: Peshier, Cassing, PRL 94 (2005) ; Cassing, arXiv: [nucl-th], NPA‘07 Cassing, arXiv: [nucl-th], NPA‘07

Basic concepts of Hadron-String Dynamics for each particle species i (i = N, R, Y, , , K, …) the phase-space density f i follows the transport equations with the collision terms I coll describing:  elastic and inelastic hadronic reactions  formation and decay of baryonic and mesonic resonances (for inclusive production: BB -> X, mB -> X, X =many particles)  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´