In relativistic nuclear collisions the production of hadrons with light (u,d,s) quarks is quantitatively described in the framework of the Statistical Hadronization Model (SHM). Charm quarks are dominantly produced in initial hard collisions but inte
ract strongly in the hot fireball and thermalize. Therefore charmed hadrons can be incorporated into the SHM by treating charm quarks as impurities with thermal distributions, while the total charm content of the fireball is fixed by the measured open charm cross section. We call this model SHMc and demonstrate that with SHMc the measured multiplicities of single charm hadrons in lead-lead collisions at LHC energies can be well described with the same thermal parameters as for (u,d,s) hadrons. Furthermore, transverse momentum distributions are computed in a blast-wave model, which includes the resonance decay kinematics. SHMc is extended to lighter collision systems down to oxygen-oxygen and includes doubly- and triply-charmed hadrons. We show predictions for production probabilities of such states exhibiting a characteristic and quite spectacular enhancement hierarchy.
We study the influence of global baryon number conservation on the non-critical baseline of net baryon cumulants in heavy-ion collisions in a given acceptance, accounting for the asymmetry between the mean-numbers of baryons and antibaryons. We deriv
e the probability distribution of net baryon number in a restricted phase space from the canonical partition function that incorporates exact conservation of baryon number in the full system. Furthermore, we provide tools to compute cumulants of any order from the generating function of uncorrelated baryons constrained by exact baryon number conservation. The results are applied to quantify the non-critical baseline for cumulants of net proton number fluctuations obtained in heavy-ion collisions by the STAR collaboration at different RHIC energies and by the ALICE collaboration at the LHC. Furthermore, volume fluctuations are added by a Monte Carlo procedure based on the centrality dependence of charged particle production as measured experimentally. Compared to the predictions based on the hadron resonance gas model or Skellam distribution a clear suppression of fluctuations is observed due to exact baryon-number conservation. The suppression increases with the order of the cumulant and towards lower collision energies. Predictions for net proton cumulants up to the eight order in heavy-ion collisions are given for experimentally accessible collision energies.
In this report we present the first quantitative determination of the correlations between baryons and anti-baryons induced by local baryon number conservation. This is important in view of the many experimental studies aiming at probing the phase st
ructure of strongly interacting matter. We confront our results with the recent measurements of net-proton fluctuations reported by the CERN ALICE experiment. The role of local baryon number conservation is found to be small on the level of second cumulants.
This document reflects thoughts on opportunities from high-energy nuclear collisions in the 2020s.
Calculations and predictions are presented within the framework of the statistical hadronization model for transverse momentum spectra of the charmonium states J/$psi$, $psi(2S)$ and $X(3872)$ produced in nucleus-nucleus collisions at LHC energies. T
he results are confronted with available data and exhibit very good agreement by using particle flow profiles from state-of-the-art hydrodynamic calculations. For $X(3872)$ production in Pb-Pb collisions we predict a transverse momentum distribution similar in shape to that for J/$psi$ with a strong enhancement at low transverse momenta and a production yield of about 1% relative to that for J/$psi$.
We propose a resolution of the discrepancy between the proton yield predicted by the statistical hadronization approach and data on hadron production in ultra-relativistic nuclear collisions at the LHC. Applying the S-matrix formulation of statistica
l mechanics to include pion-nucleon interactions, we reexamine their contribution to the proton yield, taking resonance widths and the presence of nonresonant correlations into account. The effect of multi-pion-nucleon interactions is estimated using lattice QCD results on the baryon-charge susceptibility. We show that a consistent implementation of these features in the statistical hadronization model, leads to a reduction of the predicted proton yield, which then quantitatively matches data of the ALICE collaboration for Pb-Pb collisions at the LHC.
The study of multiplicity distributions of identified particles in terms of their higher moments is at the focus of contemporary experimental and theoretical studies. In a thermalized system, combinations of these moments are directly related to the
Equation of State (EoS). The ultimate goal of the experimental measurements in relativistic nuclear collisions is, by systematic comparison to QCD and QCD inspired calculations, to probe the dynamics of genuine phase transitions between a hadron gas and the quark-gluon plasma. However, the comparison between experiment and theory is far from trivial, because several non-dynamical effects on fluctuations need to be controlled prior to a meaningful comparison to theoretical predictions. In this report we present quantitative estimates for these non-dynamical contributions using the Canonical Ensemble (CE) formulation of statistical mechanics. Together with analytical formulas we provide also results from Monte Carlo (MC) simulations within the CE and compare our predictions with the corresponding measurements from the STAR experiment.
This document summarizes thoughts on opportunities in the soft-QCD sector from high-energy nuclear collisions at high luminosities.
We summarize our current understanding of the connection between the QCD phase line and the chemical freeze-out curve as deduced from thermal analyses of yields of particles produced in central collisions between relativistic nuclei.
A Nd:YAG laser was used to simulate charged particle tracks at known positions in the CERES Time Projection Chamber at the CERN SPS. The system was primarily developed to study the response of the readout electronics and to calibrate the electron dri
ft velocity. Further applications were the determination of the gating grid transparency, the chamber position calibration, and long-term monitoring of drift properties of the gas in the detector.
