Open and Hidden Charm in Proton–nucleus and Heavy-Ion Collisions

Abstract

We review the collectivity and the suppression pattern of charmed mesons -produced in proton-nucleus and nucleus-nucleus collisions at SPS (∼ 158 A·GeV) and RHIC energies (∼ 21 A·TeV) -in comparison to dynamical and thermal models. In particular, we examine the charmonium 'melting' and the 'comover dissociation' scenarios -implemented in a microscopic transport approach -in comparison to the available data from the SPS and RHIC. The analysis shows that the dynamics of c,c quarks at RHIC are dominated by partonic or 'pre-hadronic' interactions in the strongly coupled plasma stage and can neither be modeled by 'hadronic' interactions nor described appropriately by color screening alone. Both the 'charmonium melting' and the hadronic 'comover absorption and recreation model' are found, however, to be compatible with the experimental observation at SPS energies; the experimental ratio of Ψ ′ /J/Ψ versus centrality clearly favors the 'hadronic comover' scenario. We find that the collective flow of charm in the purely hadronic Hadron-String Dynamics (HSD) transport appears compatible with the data at SPS energies, but substantially underestimates the data at top RHIC energies. Thus, the large elliptic flow v 2 of D-mesons and the low R AA (p T ) of J/Ψ seen experimentally have to be attributed to early interactions of non-hadronic degrees of freedom. Simultaneously, we observe that non-hadronic interactions are mandatory in order to describe the narrowing of the J/Ψ rapidity distribution from pp to central Au + Au collisions at the top RHIC energy of √ s = 200 GeV. We demonstrate additionally that the strong quenching of high-p T J/Ψ's in central Au + Au collisions indicates that a large fraction of final J/Ψ mesons is created by a coalescence mechanism close to the phase boundary. Throughout this review we, furthermore, provide predictions for charm observables from Au+Au collisions at FAIR energies of 25 -35 A·GeV.

Sub-threshold strangeness and charm production in UrQMD

“…This branching ratio is two orders of magnitude smaller than the corresponding decay into a φ meson. First we can compare the obtained Λ c and J/Ψ production cross sections with previous near threshold estimates [46,47], as shown in figures 4 and 5. Our estimates are in reasonable agreement (J/Ψ) or even very conservative estimates (Λ c ) as compared to previous work.…”

“…We can utilize the decays of the most massive N * resonances implemented in UrQMD, namely the N * → N + φ p+p->D+D+X SIS100 Figure 5. Comparison of the J/Ψ production yield in p+p and central A+A collisions from the UrQMD approach (symbols) with previous theoretical estimates (green short dashed) [47].…”

Dilepton production by dynamical quasi-particles in the strongly interacting quark–gluon plasma

“…10. On the other hand, simulations in transport theory [75] have shown that the local energy densities achieved in the course of heavy-ion collisions at SPS and RHIC energies reach at most 20 GeV/fm 3 ; this region is high-lighted in Fig. 10 by a shadowed area.…”

Possibility forJ/ψsuppression in high-multiplicity proton-proton collisions atsNN=7TeV

“…To model the initial state for the J/Ψ-particles one needs the momentum distribution and the spatial distribution at the production points. For the momentum distribution of the produced charmonia at SPS we use an ansatz from [34].…”

“…The exponent for the transverse distribution is b pT = 2.08 GeV −1 [34]. Our spatial distribution for the charmonium production at SPS is based on the Glauber model and calculated using the UrQMD model.…”