Color Screening Melts Quarkonium

Abstract

We calculate quarkonium spectral functions in a quark-gluon plasma using a potential model based on full QCD lattice calculations of the free energy of a static quark-antiquark pair. We estimate the binding energy and the thermal width of different quarkonium states. The estimated upper limit for the dissociation temperatures is considerably lower than the ones suggested in the recent literature.

Ground and excited state charmonium production inp+pcollisions ats=200 GeV

“…In addition, the J/ψ suppression observed in heavy ion collisions cannot be completely understood without a knowledge of the feed-down fraction of excited charmonium state decays to the J/ψ. This is particularly true under the assumption that the suppression is due to the disassociation of charmonium in the high temperature quark-gluon plasma, since lattice calculations [2] indicate that the melting points of the χ c and ψ ′ states are lower than that of the J/ψ. In this work the feed-down fractions to the J/ψ from excited charmonium states are measured, since they can be determined more precisely than production cross sections as various systematic uncertainties cancel.…”

“…Spectral function computations [2] indicate that the χ c and ψ ′ states should dissociate due to color screening at a lower temperature in hot nuclear matter than the J/ψ. One of the most important implications of the observed feed-down fractions is that the complete dissociation of the χ c and ψ ′ states would lead to a 42 ± 9 % J/ψ suppression.…”

“…Charm quarks are predominantly produced in initial gluon interactions at √ s = 200 GeV; therefore, they are sensitive to the gluon distribution in the nucleon and its modification in the nucleus. Color screening of the cc state in quark gluon plasma makes charmonium dissociation an important signature for the formation of a deconfined state of matter in A+A collisions [1,2]. However, such studies rely on an accurate understanding of charmonium production in p+p collisions, which is the goal of the present work.…”

High transverse momentum quarkonium production and dissociation in heavy ion collisions

“…The sizes of the higher excited states are larger, and the sizes of the bottomonia are smaller than the corresponding charmonia. The presence of a thermal medium screens the interactions between the Q andQ and leads to melting at some characteristic temperature [2] that depends on the meson. This picture suggests that it may be possible to observe sequential melting of narrower quarkonia as we explore thermal media of increasing temperatures [3,4].…”

“…For a quarkonium which is stationary or slowly moving through the thermal medium it might be safe to assume that it reaches thermal equilibrium with the medium. In this picture, the wavefunction of the quarkonium (the lowest Fock component) is better described by the solution of the Schrödinger equation with a modified potential that depends on the temperature [2,[8][9][10]. The potentials used are based on finite temperature lattice calculations of the potential between two static charges [33].…”