The energy loss of fast partons (quarks or gluons) in relativistic heavy-ion collisions can provide information on parton energy-loss mechanisms in a quark-gluon plasma (QGP) and serve to probe its microscopic structure. Understanding the parton energy-loss processes as partons propagate through a QGP requires measurement of large transverse momentum (high-pT) hadrons and jets. Suppression of...
QCD jets play a central role in probing QCD at high precision and in new physics searches at colliders. They are also extensively studied in ultra relativistic heavy ion collisions as multi-dimensional probes of the quark gluon plasma (QGP) that is created in the aftermath of the collisions. While the theory for jet evolution in vacuum is well established, in the presence of a hot and dense...
We present a new approach to jet substructure in heavy-ion collisions based on the study of correlation functions of energy flow operators (energy correlators). This approach is based on the insight that the dynamics of the QGP is imprinted at specific time scales in the jet, which will be reflected as changes in the shape of the correlator. We analyze the two-point correlator of an in-medium...
Hard probes are produced at early stages of heavy ion collisions and carry with them information about the medium they traverse before being detected. Some of them are elementary, but some, like quarkonia are complex. In this talk I shall argue that it is interesting to consider such complex hard probes from the point of view of open quantum systems. I shall in particular establish interesting...
Over the last decades, the theoretical picture of how hadronic jets interact with nuclear matter has been extended to account for the medium’s finite longitudinal length and expansion. However, only recently a first-principle approach has been developed that allows to couple the jet evolution to the medium flow and anisotropic structure in the dilute limit. In this talk, I will show how to...
Historically, high-pT radiative energy loss is calculated under the assumptions of the optically thin or optically thick medium within pQCD. These are two limiting (and opposite) approximations, corresponding to a jet experiencing only one or an infinite number of scatterings with medium constituents, respectively. However, in general, QGP created at the RHIC and the LHC is estimated to have...
EPOS4 is a (recently released) multipurpose event generator for simulating high energy proton-proton and nucleus-nucleus collisions, which allows to treat within the same formalism very high pt processes and also low-pt phenomena. We will first present the basic ideas, and then discuss applications concerning high-pt particle production as well as collective effects in high-multiplicity pp...
We discuss two topics in hydrodynamic description of QGP fluids in high-energy nuclear collisions. We first constrain the initial conditions in the Bjorken expansion model by considering causality. When the system is far away from local equilibrium, the relativistic hydrodynamic equations tend to violate the causality. Within the conformal fluids in one-dimensionally expanding system, we find...
We simulate the space-time dynamics of high-energy collisions based on a microscopic kinetic description in the conformal relaxation time approximation, in order to determine the range of applicability of an effective description in relativistic viscous hydrodynamics [1,2]. We find that hydrodynamics provides a quantitatively accurate description of collective flow when the average inverse...
Properties of quark gluon plasma (QGP) have been studied in high-energy nuclear collisions. Since it is difficult to describe the dynamical phenomena by first-principle calculations, an approach via phenomenological models is indispensable to scrutinize the QGP properties through experimental data. We have developed a Monte Carlo event generator based on the hydrodynamic picture of the QGP,...
The ATLAS collaboration has analyzed event-to-event fluctuations of the transverse momentum per particle as a function of the particle multiplicity. In the most central collisions, the variance of fluctuations decreases steeply. I show that this can be explained simply, provided that one takes into account two combined effects: First, for a fixed collision multiplicity, the impact parameter...
The hydrodynamic flow-like behavior of charged hadrons in high-energy lead-lead collisions is studied through their multiparticle correlations. The elliptic anisotropy harmonic values based on different orders of multiparticle cumulants, v2{2k}, are measured up to the tenth order (k = 5) as functions of the collision centrality at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The data...
The azimuthal anisotropy of the observed distribution of hadrons results from the anisotropy of the initial conditions. A more detailed picture is in principle provided by correlations of the flow coefficients in various kinematic regions. This includes the decorrelation of flow anisotropy in rapidity, the correlation of the anisotropy with mean pt, or the decorrelation of the anisotropy in...
Recent developments on a deep learning feed-forward network for estimating elliptic flow (v2) coefficients in heavy-ion collisions have shown us the prediction power of this technique. The success of the model is mainly the estimation of v2 from final state particle kinematic information and learning the centrality and the transverse momentum (pT) dependence of v2. The deep learning model is...
The initial pre-equilibrium stage of a heavy ion collision can have a significant impact on hard probes of the quark gluon plasma such as jets and heavy quarks. In weak coupling QCD the properties of this pre-equilibrium phase can be understood by effective kinetic theory, which can follow the development of the system from the glasma to hydrodynamics. We compute the jet quenching parameter...
We study the interaction of leading jet partons in a strongly interacting quark-gluon plasma (sQGP) medium based on the effective dynamical quasi-particle model (DQPM). The DQPM describes the non-perturbative nature of the sQGP at finite temperature T and baryon chemical potential μB based on a propagator representation of massive off-shell partons (quarks and gluons) whose properties...
Typically, the bulk properties of Quark Gluon Plasma (QGP) are studied using the low-pt data. However, the high-pt probes can also serve as powerful tomography tools, since they are sensitive to global QGP features, such as different temperature profiles or initial conditions. In this study, we try to determine if it is possible to constrain the η/s of the medium formed in the heavy-ion...
We present a new model for jet quenching from coherent radiation in a brick medium. The jet energy loss is simulated as a perturbative final-state vacuum parton shower followed by a medium-induced shower originating from elastic and radiative collisions with the medium constituents. Coherency is achieved by starting with trial gluons that acts as field dressing of the initial jet parton. These...
In high-energy proton-nucleus (pA) collisions, an incoming energetic parton crosses the target nucleus and suffers medium-induced, fully coherent gluon radiation. I will review the theoretical status of this effect, and present the phenomenological consequences of the corresponding fully coherent energy loss (FCEL) on light hadron, heavy meson and quarkonium production in pA collisions. I will...
In this work we use linearized QCD kinetic to study how highly energetic parton -proxy for a jet- interacts with the hot Quark-Gluon Plasma (QGP), We find that the parton loses energy to the medium mainly through a radiative turbulent gluon cascade, down to the temperature, at which dissipation starts taking place. The distribution of energy takes place in two stages, first, a highly...
Hybrid Hadronization is based on the idea of describing hadronization at short and long distances by different hadronization models, namely parton recombination, and string fragmentation. The latter dominates in the vacuum at large energies. The former becomes important at lower energies and in the presence of a bath of partons, e.g. for jet showers or heavy quarks in quark gluon plasma....
Results obtained from dilepton measurements over the past 25 years at energies from SPS energies up to RHIC and LHC energies will be reviewed. The motivation for extending these measurements to lower energies will be discussed with emphasis on the onset of the deconfinement phase transition, the onset of chiral symmetry restoration and the search for a first order phase transition. The current...
We investigate the fluctuations of the net-baryon number density in dense hadronic matter. Chiral dynamics is modeled via the parity doublet Lagrangian, and the mean-field approximation is employed to account for chiral criticality. We focus on the qualitative properties and systematics of the second-order susceptibility of the net-baryon number density for individual positive- and...
We study equilibrium as well as out-of-equilibrium properties of the strongly interacting QGP medium under extreme conditions of high temperature T and high baryon densities or baryon chemical potentials μB within a kinetic approach. We present the thermodynamic and transport properties of the QGP close to equilibrium in the framework of effective models with Nf=3 active quark flavors such as...
The hydrodynamic modelling of heavy-ion collisions at energies from few to tens of GeV per NN pair brings new challenges as compared to simulations at top RHIC or LHC energies. The contraction of the incoming nuclei is much weaker resulting in a long inter-penetration phase and a more complex initial-state geometry. Conventional hydrodynamic models, where the fluid phase starts at a fixed...
Exploring the space-time extent of particle production is an important goal of heavy-ion physics, and substantial effort has been made in order to understand the underlying physics behind the experimental observations of non-Gaussian behavior, in particular with respect to connections to the phase diagram. In experiments, femtoscopic (momentum) correlations are utilized to gain information...
The spin Hall effect (SHE) is a generation of spin polarization for moving spin carriers in materials under an external electric field and has been observed in semiconductors, metals, and insulators at or below room temperature. Recent theoretical analyses show that spin Hall current can be induced by the baryon chemical potential gradient which plays the role of the analogous electric field...
The kinetic-theory-wise formulation of relativistic dissipative nonresistive magnetohydrodynamics for massive spin-half particles in the presence of a magnetic field is presented. Using a relaxation-time approximation for the collision kernel of the underlying relativistic Boltzmann equation the nonequilibrium corrections to the phase-space distribution function and multiple transport...
The strongly-coupled nature of the quark-gluon plasma was discovered nearly twenty years ago. Since that time, we have learned a great deal about the sQGP and its transport properties, but the question of how quarks and gluons, the microscopic degrees of freedom, produce the near-perfect liquid properties observed in the bulk remains open. The sPHENIX experiment, the first collider detector...
The ALICE collaboration pursues several upgrades to further extend the reach of heavy-ion physics at the LHC. For LHC Run 4 (2029-2032), ALICE is pioneering the use of bent, wafer-scale pixel sensors to produce truly cylindrical tracking layers with very low material budget to replace the three innermost layers of the inner tracking system. The resulting improvement in pointing resolution will...
Hydrodynamic simulations of the quark-gluon plasma (QGP) permit us not only to gauge the transport properties of hot QCD matter from data, but also to constrain the conditions that set the stage for the formation of such matter. Recent measurements from RHIC and LHC demonstrate that the QGP initial condition is impacted by the shape and radial structure of the colliding nuclei. Based on a...
Heavy quark production represents one of the main tools for the QGP characterization, as shown by the vast amount of results obtained in nuclear collisions at collider energies. At fixed-target energies, these measurements become more difficult because of the vanishing production cross sections, and for the moment only charmonium results at top SPS energy (sqrt(s_NN)=17 GeV) are available. A...
The production of heavy-flavour hadrons in hadronic collisions can be calculated with a factorisation approach, as a product of parton distribution functions (PDFs), partonic hard- scattering cross section, and parton-to-hadron fragmentation functions, assumed to be universal among different collision systems. Recent measurements of baryon-to-meson production yield ratios at the LHC, observed to...
In ultra-relativistic heavy-ion collisions, a dense and hot QCD medium, the Quark-Gluon Plasma (QGP) is created. Heavy quarks (charm and beauty) are produced dominantly in hard partonic scatterings in the early stage of the collisions and experience the whole medium evolution. Measurements of open heavy-flavor hadron production provide information on the transport properties of the QGP, the...
Multiparton interactions in proton-proton collisions have long been a topic of great interest. A new look at them has begun to emerge from work being done to understand the dynamics of ‘small systems’, a topic that is taking center stage in the physics of relativistic heavy-ion interactions. Numerous studies conducted at the LHC and lower energies reveal that proton-proton collisions at high...
We present the first microscopic model, which allows to describe the formation of charmonia in ultrarelativistic heavy ion collisions. We follow the heavy quarks from their initial production in hard collisions, followed by their passage through the quark gluon plasma where the heavy quarks interact with the plasma constituents and among themselves with a potential obtained by lattice gauge...
The global picture of quarkonia production in heavy ions collisions has recently reached some good consensus in the community.
However, before turning it into a precision tool to better characterize QGP, some theoretical challenges still need to be met.
In this talk, I will review some of the recent progress achieved for the description of quarkonia production, focusing on both fully quantum...
The behavior of quarkonia and open-heavy flavour hadrons in hadronic collisions provide a unique testing ground for understanding quantum chromodynamics (QCD). Although there has been significant progress, our understanding of hadronic collisions has been challenged by the observation of intriguing effects in high-multiplicity proton-proton and proton-Pb collisions, such as the discovery of...
The heavy quark momentum diffusion coefficient (𝜅) is one of the most important ingredients for the Langevin description of the heavy quark dynamics. In the temperature regime relevant for the heavy ion collision phenomenology, there exists a substantial difference between the lattice estimations of 𝜅 and the corresponding leading order (LO) result from the hard thermal loop (HTL) perturbation...
The statistical hadronization model is very successful in reproducing the experimental data in Pb-Pb collisions, both for light-quark and heavy-quark hadrons. In particular the detailed comparisons for charmonium lead us to infer quasi-complete thermalization of charm quarks in QGP and concurrent hadronization with the lighter quarks. The large yield measured for the Λc baryon at the LHC can...
As a hadronization model in relativistic heavy-ion collisions, coalescence (recombination) model has achieved great success in the description of the production of hadron and light nuclei. This talk focuses on light-nuclei production within the framework of the coalescence model. By employing the characteristic function of the phase space density, we derive the yield of light nuclei in terms...
We describe multiquark clusters in quark matter within a Beth-Uhlenbeck approach in a background gluon field that is coupled to the underlying chiral quark dynamics using the Polyakov-gauge and an effective potential for the traced Polyakov-loop. A higher multiquark cluster of size n is described as a binary composite of smaller subclusters n1 and n2 (n1+n2=n ) with a bound state and...
