Quarkonium formation at high energy

Thews, Robert L.

doi:10.1016/s0375-9474(02)00721-2

Cited by 21 publications

(28 citation statements)

References 8 publications

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“…The absolute value of this formation was found to be very sensitive to the underlying charm quark momentum distributions [ 2]. There is also quite strong variation of the results which depend on largely unconstrained model parameters involving details of the size and expansion profile of the deconfinement region.…”

Section: Introductionmentioning

confidence: 90%

“…Conversely, one expects that initial production will increase in relative importance for very peripheral collisions. To get an approximate idea of how this effect will appear, we revert to our original model calculations which included the absolute magnitude results [ 2]. One relevant parameter is the number of initial pairs, N cc , parameterized by its value at zero impact parameter.…”

Section: Centrality Behaviormentioning

confidence: 99%

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Formation of charmonium states in heavy-ion collisions and thermalization of charm

Thews

2006

Eur. Phys. J. A

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Abstract. We examine the possibility to utilize in-medium charmonium formation in heavy ion interactions at collider energy as a probe of the properties of the medium. This is possible because the formation process involves recombination of charm quarks which imprints a signal on the resulting normalized transverse momentum distribution containing information about the momentum distribution of the quarks. We have contrasted the transverse momentum spectra of J/ψ, characterized by p T 2 , which result from the formation process in which the charm quark distributions are taken at opposite limits with regard to thermalization in the medium. The first uses charm quark distributions unchanged from their initial production in a pQCD process, appropriate if their interaction with the medium is negligible. The second uses charm quark distributions which are in complete thermal equilibrium with the transversely expanding medium, appropriate if a very strong interaction between charm quarks and medium exists. We find that the resulting p T 2 of the formed J/ψ should allow one to differentiate between these extremes, and that this differentiation is not sensitive to variations in the detailed dynamics of in-medium formation. We include a comparison of predictions of this model with preliminary PHENIX measurements, which indicates compatibility with a substantial fraction of in-medium formation.

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Section: Introductionmentioning

confidence: 90%

Section: Centrality Behaviormentioning

confidence: 99%

Formation of charmonium states in heavy-ion collisions and thermalization of charm

Thews

2006

Eur. Phys. J. A

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“…Understanding the data, however, turned out to be more complicated. The reason is that the suppression pattern seen is not only due to the hot medium effects of screening, but more like due to the interplay of this with effects of cold nuclear matter [4], as well as those of recombination [5]. In order to disentangle these different effects we must know the properties of quarkonium in-medium and determine their dissociation temperatures.…”

Section: Why Are We Interested?mentioning

confidence: 99%

Potential models for quarkonia

Mócsy

2009

Eur. Phys. J. C

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Abstract. In this paper I discuss what we can learn about quarkonium dissociation from lattice-potential based models. Special emphasis is given to results obtained in agreement by different models, and to the relevance of lattice QCD for potential models. Future directions are also discussed. PACS. PACS-key discribing text of that key -PACS-key discribing text of that keyWhy are we interested?One of the aims of relativistic heavy ion collisions is to produce quark-gluon plasma (QGP), a state of matter in which the constituents of our hadronic world are deconfined. Deconfinement is expected to happen at large energy densities, which can be obtained by heating matter to extreme high temperatures. High energy density matter has been already produced at SPS CERN and at RHIC BNL, and will be produced at the LHC, which just started its operation at CERN. To have control over what temperatures are achieved and whether deconfined matter has been produced we need a thermometer. The sequential melting of quarkonium has been long considered to be exactly that: the QGP thermometer [1]. In a deconfined matter the force between the constituents of a quarkonium state, a heavy quark and its antiquark, is weakened by the color screening produced by the light quarks and gluons. For twenty years it has been believed that this screening leads to the dissociation (melting) of quarkonium [2]. The different quarkonium states are expected to melt sequentially, at different temperatures. A suppressed yield of quarkonium can be visible in the dilepton spectrum, which is measured in experiments.J/ψ suppression has been indeed measured by the different experiments [3]. Understanding the data, however, turned out to be more complicated. The reason is that the suppression pattern seen is not only due to the hot medium effects of screening, but more like due to the interplay of this with effects of cold nuclear matter [4], as well as those of recombination [5]. In order to disentangle these different effects we must know the properties of quarkonium in-medium and determine their dissociation temperatures.a e-mail: amocsy@pratt.eduIn principle, everything about a given quarkonium channel is embedded in its spectral function: The position of a peak in the spectral function corresponds to the mass of a bound state, while its width determines its lifetime. Melting of a state corresponds to the disappearance of a peak. A spectral function also contains information about the continuum and its threshold. So following how the spectral function changes with temperature can give us a theoretical insight to the temperature-dependence of quarkonium properties. There are two main lines of theoretical studies to determine quarkonium spectral functions at finite temperature: potential models and lattice QCD. Potential models have been widely used to study quarkonium, but their applicability at finite temperature is still under scrutiny. Lattice QCD provides the most straightforward way to determine spectral functions, but the results suffer from discretiza...

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“…The in-medium formation picture we consider here uses competing formation and dissociation reactions in a Boltzmann equation to calculate the final J/ψ population. The absolute value of this formation was found to be very sensitive to the underlying charm quark momentum distributions [7]. In addition, there is significant dependence on details of the size and expansion profile of the deconfinement region, for which various model parameters must be introduced.…”

mentioning

confidence: 99%

“…Conversely, one expects that initial production will increase in relative importance for very peripheral collisions. To get an approximate idea of how this effect will appear, we revert to our original model calculations which included the absolute magnitude results [7]. The relevant parameter is the number of initial pairs, N cc , parameterized by its value at zero impact parameter.…”

mentioning

confidence: 99%

In-Medium Formation of J/Psi as a Probe of Charm Quark Thermalization

Thews¹

2006

AIP Conference Proceedings

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Abstract. Charmonium formation via charm quark in-medium recombination in heavy ion interactions at collider energies has the potential to probe some properties of the medium by utilizing the sensitivity of the recombination process to the momentum distribution of the quarks. We have examined the transverse momentum spectra of J/ψ, characterized by p T 2 , which result from the formation process in which the charm quark distributions are unchanged from their initial production in a pQCD process. This is contrasted with the case in which the charm quarks have completely come into thermal equilibrium with an expanding medium whose properties are determined by the spectra of produced light hadrons. We find that the resulting p T 2 of the formed J/ψ provide a distinct signature of the underlying charm quark spectra, and that signature is essentially independent of the detailed dynamics of the in-medium formation reaction. In addition, both of these signatures are sufficiently separated from the case in which no in-medium formation takes place. Finally, utilizing a model for the fraction of J/ψ which originate from in-medium formation, we predict the centrality behavior of these signatures.The role of J/ψ produced in high energy heavy ion collisions as a signature for color deconfinement [1] has evolved in recent years with the realization that at collider energies an additional formation mechanism may become significant [2,3]. This depends on the initial production of multiple cc pairs in sufficient numbers. Initial estimates [4] from extrapolation of fixed-target data put this number at about 10 for central Au-Au collisions at RHIC. Subsequently, measurements by the PHENIX and STAR experiments indicate even higher numbers, between 20 [5] and 40 [6], respectively. The in-medium formation picture we consider here uses competing formation and dissociation reactions in a Boltzmann equation to calculate the final J/ψ population. The absolute value of this formation was found to be very sensitive to the underlying charm quark momentum distributions [7]. In addition, there is significant dependence on details of the size and expansion profile of the deconfinement region, for which various model parameters must be introduced. The initial PHENIX data [8] suffered from low statistics, and was compatible with a fairly large region of model parameter space [9].Recent work in this area concentrated on finding a signature for in-medium J/ψ formation which is independent of the detailed dynamics and magnitude of the formation. We found that the p T spectrum of the formed J/ψ may provide such a signature [10]. Our first calculations of in-medium formation used initial charm quark momentum distributions from NLO pQCD amplitudes to generate a sample of cc pairs, supplemented by an initial-state transverse momentum kick to simulate confinement and nuclear ef-

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Quarkonium formation at high energy

Cited by 21 publications

References 8 publications

Formation of charmonium states in heavy-ion collisions and thermalization of charm

Formation of charmonium states in heavy-ion collisions and thermalization of charm

Potential models for quarkonia

In-Medium Formation of J/Psi as a Probe of Charm Quark Thermalization

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