Charmonium in heavy ion collisions Olena Linnyk 16

Charmonium in heavy ion collisions Olena Linnyk 16 July 2007

Anomalous J/Y suppression Charm sector reflects the dynamics in the early phase of heavy-ion collisions ! J/Y ‚normal‘ absorption by nucleons (Glauber model) Experimental observation (NA 38/50/60): extra suppression in A+A collisions; increasing with centrality

Scenarios for anomalous charmonium suppression • Comover absorption • QGP colour screening [Digal, Fortunato, Satz ’ 03] Quarkonium dissociation T: Dissociation energy density ed ~ 2(Td/Tc)4 c. C melting J/Y [Gavin & Vogt, Capella et al. `97] absorption by low energy inelastic scattering with ‚comoving‘ mesons (m=p, h, r, . . . ) J/Y+m <-> D+Dbar Y´ +m <-> D+Dbar c. C +m <-> D+Dbar

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

Charmonium production in p. N Hard probe -> binary scaling! s. J/Yexp = s. J/Y + B(cc->J/Y) scc + B(Y´->J/Y) s. Y´

Modelling the comover scenario in HSD 1. Charmonia dissociation cross sections with p, r, K and K* mesons J/Y (cc, Y‘) + meson (p, r, K , K*) <-> D+Dbar • Phase-space model for charmonium + meson dissociation: constant matrix element 2. J/Y recombination cross sections by D+Dbar annihilation: D+Dbar -> J/Y (cc, Y‘) + meson (p, r, K , K*) are determined by detailed balance! [PRC 67 (2003) 054903]

Modeling the QGP melting in HSD Energy density e (x=0, y=0, z; t) from HSD Threshold energy densities: J/Y melting: e(J/Y )=16 Ge. V/fm 3 cc melting: e(cc ) =2 Ge. V/fm 3 ‚ ‚ Y melting: e(Y ) =2 Ge. V/fm 3 [Olena Linnyk et al. , nucl-th/0612049, NPA 786 (2007) 183 ]

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

Comparison to data

Pb+Pb and In+In @ 158 A Ge. V comover absorption Pb+Pb and In+In @ 160 A Ge. V consistent with the comover absorption for the same parameter set! [OL et al NPA 786 (2007) 183]

Pb+Pb and In+In @ 158 A Ge. V QGP threshold melting Y´ absorption too strong, which contradict data [OL et al NPA 786 (2007) 183] ‚ e(J/Y )=16 Ge. V/fm 3, e(cc ) =e(Y ) =2 Ge. V/fm 3

Au+Au @ s 1/2=200 Ge. V Comover absorption Energy density cut ecut=1 Ge. V/fm 3 reduces the meson comover absorption || Space for partonic effects In the comover scenario the J/Y suppression at midrapidity is stronger than at forward rapidity, unlike the data! [OL et al ar. Xiv: 0705. 4443]

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

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 Te. V; exp. data ?

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

p J/Y probes early stages of fireball and HSD is the tool to model it. p Comover absorption and threshold melting both reproduce J/Y survival in Pb+Pb as well as in In+In @ 158 A Ge. V, while Y´ data are in conflict with the melting scenario. p Comover absorption and colour screening fail to describe Au+Au at s 1/2=200 Ge. V at mid- and forward rapidities simultaneously. p 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

ar. Xiv: 0705. 4443 nucl-th/0612049 ar. Xiv: 0704. 1410

Back-up slide 1 local energy densityvs Bjorken energy density • transient time for central Au+Au at 200 Ge. V: Y t ~ 2 R /g ~ 0. 13 fm/c J/Y • cc formation time: t ~ 1/M ~ 1/4 Ge. V ~ 0. 05 fm/c < t c • cc pairs are produced in the initial NN collisions in time period t ‚ r c C A cm T r r Bjorken energy density: AT is the nuclei transverse overlap area t is the formation time of the medium at RHIC e. Bj t ~ 5 Ge. V/fm 2/c ‚Local‘ energy density e during transient time tr : e ~ 5[Ge. V/fm 2/c] / [0. 13 fm/c] ~ 30 Ge. V/fm 3 accounting t. C : e~ 28 Ge. V/fm 3 ü HSD reproduces PHENIX data for Bjorken energy density very well ü 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: using the quark spectral functions from the Dynamical Quasi. Particle Model (DQPM) ( approximation to QCD DQPM: Peshier, Cassing, PRL 94 (2005) 172301; Cassing, ar. Xiv: 0704. 1410[nucl-th], NPA‘ 07 Partonic phase: quarks and gluons (= ‚dynamical quasiparticles‘) with offshell spectral functions (width, mass) defined by DQPM elastic and inelastic parton-parton interactions: using the effective cross sections from the DQPM ü q + qbar (flavor neutral) <=> gluon (colored) ü gluon + gluon <=> gluon (possible due to large spectral width) ü 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 baryon Hadronic phase: hadron-string interactions – off-shell HSD

Basic concepts of Hadron-String Dynamics • for each particle species i (i = N, R, Y, p, r, K, …) the phase-space density f follows the transport equations q q q i with the collision terms Icoll describing: elastic and inelastic hadronic reactions BB <-> B´B´, BB <-> B´B´m, m. B <-> m´B´, m. B <-> B´ formation and decay of baryonic and mesonic resonances string formation and decay (for inclusive production: BB->X, m. B->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