We investigate the transition from suppression to enhancement of J/ψ mesons produced in ultra-relativistic nuclear collisions in the framework of the statistical hadronization model. The calculations ...are confronted with the most recent data from the RHIC accelerator. This comparison yields first direct evidence for generation of J/ψ mesons at the phase boundary. Based on the success of this approach we make specific predictions for LHC energy.
This document summarizes the efforts of the EMMI Rapid Reaction Task Force on “Suppression and (re)generation of quarkonium in heavy-ion collisions at the LHC”, centered around their 2019 and 2022 ...meetings. It provides a review of existing experimental results and theoretical approaches, including lattice QCD calculations and semiclassical and quantum approaches for the dynamical evolution of quarkonia in the quark-gluon plasma as probed in high-energy heavy-ion collisions. The key ingredients of the transport models are itemized to facilitate comparisons of calculated quantities such as reaction rates, binding energies, and nuclear modification factors. A diagnostic assessment of the various results is attempted and coupled with an outlook for the future.
We construct net baryon number and strangeness susceptibilities as well as correlations between electric charge, strangeness and baryon number from experimental data on the particle production yields ...at midrapidity of the ALICE Collaboration at CERN. The data were taken in central Pb-Pb collisions at sNN=2.76 TeV and cover one unit of rapidity. We show that the resulting fluctuations and correlations are consistent with Lattice QCD results at the chiral crossover pseudocritical temperature Tc≃155 MeV. This agreement lends strong support to the assumption that the fireball created in these collisions is of thermal origin and exhibits characteristic properties expected in QCD at the transition from the quark gluon plasma to the hadronic phase. Since Lattice QCD calculations are performed at a baryochemical potential of μB=0, the comparisons with LHC data are the most direct due to the vanishing baryon transport to midrapidity at these high energies.
A fundamental question of physics is what ultimately happens to matter as it is heated or compressed. In the realm of very high temperature and density the fundamental degrees of freedom of the ...strong interaction, quarks and gluons, come into play and a transition from matter consisting of confined baryons and mesons to a state with ''liberated'' quarks and gluons is expected. The study of the possible phases of strongly interacting matter is at the focus of many research activities worldwide. In this paper the physical aspects of the phase diagram, its relation to the evolution of the early Universe, as well as the inner core of neutron stars are discussed. Also recent progress in the experimental study of hadronic or quark-gluon matter under extreme conditions with ultrarelativistic nucleus-nucleus collisions is summarized.
A wealth of data on charmonium production in Pb-Pb collisions from the LHC experiments has provided strong evidence for (re-)generation as a dominant production mechanism at low transverse momentum. ...We present an important extension of the statistical hadronisation model to describe J/ψ transverse momentum distributions based on input parameters from hydrodynamical simulations. Comparison to the data allows the testing of the degree of thermalisation of charm quarks in the quark-gluon plasma. To this end we will report analyses of the J/ψ transverse momentum spectra in Pb-Pb collisions at sNN=2.76and5.02TeV.
We present new results on the statistical hadronization of heavy quarks at SPS, RHIC and LHC energies. Several new aspects are considered, among them a separation of the collision geometry into a ...“core” and a “corona” part and an estimate of the annihilation rate of charm quark in a hot plasma, together with a critical assessment of its influence on the results. For RHIC energies we investigate the centrality dependence of
J
/
ψ
production focusing on the model results for different values of the charm production cross section, including its theoretical and experimental uncertainty. We also study, within this model, the rapidity dependence of the
J
/
ψ
yield. Recent RHIC data from the PHENIX experiment are well reproduced. At LHC energy, we update our model predictions for the centrality dependence of the
J
/
ψ
yield and investigate as well the rapidity dependence. We also discuss the transverse momentum distributions of
J
/
ψ
mesons expected from the model and provide predictions for a range of values of the expansion velocity at chemical freeze-out. Finally, we extend the model to predict
ϒ yields in
Pb
+
Pb
collisions at LHC energy.
We analyze recently compiled data on the production of open heavy flavor hadrons and quarkonia in e+e− as well as pp and p-nucleus collisions in terms of the statistical hadronization model. Within ...this approach the production of open heavy flavor hadrons is well described with parameters deduced from a thermal analysis of light flavor hadron production. In contrast, quarkonium production in such collisions cannot be described in this framework. We point out the relevance of this finding for our understanding of quarkonium production in ultra-relativistic nucleus–nucleus collisions.
We provide, within the hydrokinetic model, a detailed investigation of kaon interferometry in Pb+Pb collisions at LHC energy (sNN=2.76 TeV). Predictions are presented for 1D interferometry radii of ...KS0KS0 and K±K± pairs as well as for 3D femtoscopy scales in out, side and long directions. The results are compared with existing pion interferometry radii. We also make predictions for full LHC energy.
We present a comprehensive analysis of hadron production in e+e− collisions at different center-of-mass energies in the framework of the statistical model of the hadron resonance gas. The model is ...formulated in the canonical ensemble with exact conservation of all relevant quantum numbers. The parameters of the underlying model were determined using a fit to the average multiplicities of the latest measurements at s=10, 29–35, 91 and 130–200 GeV. The results demonstrate that, within the accuracy of the experiments, none of the data sets is satisfactorily described with this approach, calling into question the notion that particle production in e+e− collisions is thermal in origin.
We analyze the experimental hadron yield ratios for central nucleus–nucleus collisions in terms of thermal model calculations over a broad energy range,
s
N
N
=
2.7
–
200
GeV
. The fits of the ...experimental data with the model calculations provide the thermal parameters, temperature and baryo-chemical potential at chemical freeze-out. We compare our results with the values obtained in other studies and also investigate more technical aspects such as a potential bias in the fits when fitting particle ratios or yields. Using parametrizations of the temperature and baryonic chemical potential as a function of energy, we compare the model calculations with data for a large variety of hadron yield ratios. We provide quantitative predictions for experiments at LHC energy, as well as for the low RHIC energy of 62.4 GeV. The relation of the determined parameters with the QCD phase boundary is discussed.
PDF
