Quark-gluon plasma, which is a strongly coupled liquid at its natural length scales, must at the same time feature weakly coupled quark and gluon quasiparticles that appear only in hard processes that can resolve its short-length structure. In particular, high-energy partons in a jet shower can scatter off, and kick, the quark and gluon quasiparticles within a droplet of QGP when these Moliere...
Charmonia have long been recognized as a valuable probe of the nuclear matter in extreme conditions, such as the strongly interacting medium created in heavy-ion collisions and known as quark-gluon plasma (QGP). At LHC energies, the regeneration process due to the abundantly produced charm quarks, was found to considerably affect measured charmonium observables. Comprehensive production...
Most of our experimentally-driven knowledge about the early stages of a heavy-ion collision comes from analysis of measurements made near mid-rapidity. However, much information about the dynamics is encoded in rapidity-dependent behavior, and there exists a large amount of experimental data available to constrain this rapidity dependence. To leverage this information, we perform a systematic...
Jet energy loss and transverse momentum broadening are controlled by the jet transport coefficient $\hat{q}$ in the QGP medium. Specifically, jet energy loss correlates with jet propagation length, while transverse momentum asymmetry caused by the gradient of $\hat{q}$ depends on the initial transverse coordinates. We study both the longitudinal and transverse jet tomography in dijet events by...
The interplay of the chiral anomaly and the strong magnetic or vortical field created in the off-central heavy-ion collisions can give rise to anomalous chiral effects in the quark--gluon plasma. These include the Chiral Magnetic Effect (CME), the Chiral Magnetic Wave (CMW) and the Chiral Vortical Effect (CVE). The study of these novel phenomena is of fundamental significance since they may...
Heavy quarks are one of the most powerful probes to study the properties of quark-gluon plasma. We present new results on nuclear modification factors of $\mathrm{B}_\mathrm{s}^{0}$ and $\mathrm{B}^{+}$ mesons, using proton-proton (pp) and lead-lead (PbPb) data recorded with the CMS detector in 2017 and 2018, respectively. The measured B meson nuclear modification factors over an extended...
The recent measurements of femtoscopic correlations at NA61/SHINE, using small systems, unravel that the shape of the particle emitting source is not Gaussian. The measurements are based on alpha-stable symmetric L\'evy sources, and we discuss the average pair transverse mass dependence of the source parameters. One of the parameters, the L\'evy exponent $\alpha$, is of particularly...
Heavy quarks (charm and beauty) are valuable probes for investigating the properties of the quark-gluon plasma (QGP) formed in ultra-relativistic heavy-ion collisions, as they are mainly produced through hard-scattering processes prior to the formation of the QGP, and their number is conserved during the subsequent QGP evolution. Measurements of the nuclear modification factor $R_{\rm AA}$ of...
Using a (3+1)-dimensional hybrid framework with parametric initial conditions, we study the rapidity-dependent directed flow $v_1(y)$ of identified particles, including pions, kaons, protons, and lambdas in heavy-ion collisions. Cases involving Au+Au collisions are considered, performed at $\sqrt{s_{\rm NN}}$ ranging from 7.7 to 200 GeV. The dynamics in the beam direction is constrained using...
Hydrodynamics provides quantitative descriptions of various flow measurements in heavy-ion collisions, suggesting the strongly-coupled nature of the hot QCD matter. A ubiquitous phenomenon in fluid dynamics is the formation of vortex rings. In heavy-ion collisions, different conditions can give rise to toroidal vortex structure in the QGP medium, such as the medium's response to jet...
The suppression of jets in heavy-ion collisions can provide detailed information about the hot, dense plasma formed in these collisions at the LHC. Jet quenching in heavy-ion collisions is expected to depend on the mass of the fragmenting parton. For light partons, energy loss via gluon bremsstrahlung is expected to dominate, while for heavy-quark-initiated jets, collisional energy loss may...
Calculations of baryon number fluctuations up to the sixth order at finite temperature and density in Ref.[1] have been extended to regime of high baryon chemical potentials with 400 MeV $\leq \mu_B\leq 700$ MeV. A peak structure is found for the dependence of the kurtosis of baryon number distributions, i.e., $R^{B}_{42}=\chi^{B}_{4}/\chi^{B}_{2}$, on the collision energy in a range of 3 GeV...
The $f_0(980)$ is a candidate exotic hadron, first observed by $\pi\pi$ scattering in the 1970’s. Its configuration still remains controversial— it can be a normal $s\bar{s}$ meson, a tetraquark $s\bar{s}q\bar{q}$ state, a $q\bar{q}g$ hybrid, or a $\mathrm{K}\bar{\mathrm{K}}$ molecule. Relativistic heavy ion collisions are in a unique position to identify the $f_0(980)$ quark content by the...
The study of charm quark hadrons is an important probe to the processes of hadronization of heavy quarks. More specifically, we present results on the production of $\Lambda_\mathrm{c}$ baryon, the nuclear modification factors ($R_\mathrm{AA}$), and the $\Lambda_\mathrm{c}/\mathrm{D}^{0}$ yield ratios at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$~TeV in proton-proton (pp) collisions and in different...
The global spin alignment of particles produced in heavy-ion collisions can reveal valuable information about the strong force field and the properties of the quark-gluon plasma. The STAR collaboration recently observed a large global spin alignment of $\phi$-mesons in Au+Au collisions using the data from the first phase of the RHIC Beam Energy Scan program (BES-I) [1]. This cannot be...
Over the past decade, considerable research effort has focused on investigating macroscopic consequences of anomalies in quantum field theories. In particular, chiral matter is expected to exhibit novel transport phenomena arising from the interplay between quantum anomalies and electromagnetic and vortical fields [1]. In order to study these effects in fluid systems like the quark-gluon...
We compute the heavy quark momentum diffusion coefficient $\kappa$ using QCD effective kinetic theory for a system going through bottom-up isotropization until approximate hydrodynamization. This transport coefficient describes heavy quark momentum diffusion in the quark-gluon plasma and is used in many phenomenological frameworks, e.g. in the open quantum systems approach. Our extracted...
Predictions for the QCD critical point are made using Bayesian inference techniques within the holographic gauge/gravity correspondence. For that, we employ a Einstein-Maxwell-Dilaton (EMD) model capable of reproducing the latest lattice QCD results at zero and finite baryon density, known to predict a high-density critical endpoint. For the first time, we numerically find the posterior...
Intermediate pT jets (minijets) are created by initial hard scatterings in heavy-ion collision experiments. They can constitute a significant portion of the particle multiplicity but do not lend themselves to hydrodynamic treatment as their transverse momenta are larger than the typical saturation scale of the bulk matter.Their orientation is independent of the underlying event and they can...
Extensive studies of dijet momentum balance, inclusive jet shapes, and photon-tagged jet fragmentation functions have revealed a significant contribution of low transverse momentum ($p_\mathrm{T}$) particles to the energy momentum balance of dijet and photon-jets. Effects such as medium-induced radiation and medium response could contribute to the enhancement of low-$p_\mathrm{T}$ particles....
The hadro-chemistry of bottom quarks produced in hadronic collisions encodes valuable information on the mechanism of color-neutralization in these reactions. We first compute the chemistry of bottom-hadrons in high-energy $pp$ collisions employing statistical hadronization with a largely augmented set of states beyond the currently measured spectrum. This enables a comprehensive prediction of...
The early dynamics in heavy-ion collisions involves a rapid, far from equilibrium evolution. This early pre-equilibrium stage of the dynamics can be modeled using kinetic equations. The effect of this pre-equilibrium stage on final observables derived from transverse momenta of emitted particles is negligible. Therefore, the kinetic equations in the relaxation time approximation for a...
Previous analyses have shown a narrowing effect in the inclusive jet substructure. While this narrowing effect could be a result of jet quenching, it could also be caused due to a selection bias by which very quenched and broader jets are filtered out from the considered jet transverse momentum window. Photon-tagged jets, which correspond to a quark-enriched sample, can significantly reduce...
Subensemble Acceptance Method (SAM) [1,2] is an essential link between measured event-by-event fluctuations and their grand canonical theoretical predictions such as lattice QCD. The method allows quantifying the global conservation law effects in fluctuations. In its basic formulation, SAM requires a sufficiently large system such as created in central nucleus-nucleus collisions and...
We simulate the space-time dynamics of high-energy collisions based on a microscopic kinetic description, 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 Reynolds number $\mathrm{Re}^{−1}$ is sufficiently...
The PHENIX experiment at RHIC has a unique large rapidity coverage (1.2$<|\eta|<$2.2) for heavy flavor studies in heavy ion collisions. This kinematic region has a smaller particle density and may undergo different nuclear effects before and after the hard process when compared to mid-rapidity production. The latest PHENIX runs contains a large data set which allows, for the first time, the...
We report on progress in understanding thermalization in QCD at the full quantum level. Previous studies of thermalization of highly excited states in QCD, as they arise in heavy ion collisions, have either involved the (semi-)classical evolution of highly occupied gluon states or kinetic theory. Both approaches omit or approximate essential properties of quantum mechanical systems including...
The formation of light nuclei in heavy-ion collisions can be explained by two models: the thermal model and the coalescence model. The thermal model proposes that light nuclei originate from a thermal source where they are in equilibrium with other particles in the fireball. However, due to their low binding energies, the formed nuclei are unlikely to survive the high-temperature conditions of...
The study of jet substructure in heavy-ion collisions provides multiple tools for incisive exploration of jet-medium interactions and the mechanisms underlying jet quenching. Some results, however, remain disjoint: the jet mass and jet angularities, including girth and thrust, are strongly-correlated observables that have given seemingly conflicted answers on the angular quenching of jets...
We discuss the evolution of initial momentum anisotropy in the early-stage quark-gluon plasma. We use kinetic theory to study the far-from-equilibrium evolution of an expanding plasma with an anisotropic momentum-space distribution. We identify slow and fast degrees of freedom in the far-from-equilibrium plasma from the evolution of moments of this distribution. At late times, the slow modes...
Heavy flavor quarks (charm and bottom), produced in the early stages of heavy-ion collisions, serve as excellent probes to study the properties of the Quark-Gluon Plasma (QGP). When traversing the medium, charm quarks suffer from `jet quenching' thanks to the interactions with the QGP. It can manifest as degradation of charm quark energy and modifications to the fragmentation pattern, both of...
Quarkonia and open heavy-flavor hadrons are important probes to study the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions. Heavy quarks (charm and bottom) are primarily generated at initial hard platonic scatterings and undergo the whole QGP evolution. Therefore, they are excellent probes of the QGP properties.Production of quarkonia depends on the dissociation and...
The investigation of the quark content of hadrons has been a major goal of non-perturbative strong interaction physics. In the last decade, several resonances in the mass range 1000-2000 MeV/$c^2$ have emerged that cannot be explained by the quark model. The internal structure of exotic resonances such as $\rm f_0$, $\rm f_1$, and $\rm f_2$ is currently unknown. Different scenarios are...
This talk presents a measurement of higher order flow harmonics with order number up to 10 in lead-lead (PbPb) collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$~TeV, using data collected by the CMS experiment. Higher order flow harmonics probe the initial geometry of heavy ion collisions as well as the viscous damping of flow coefficients during the evolution of the quark-gluon plasma (QGP). By...
This talk presents new measurements of inclusive jet yield suppression and correlation with event-plane orientation to elucidate the kinematic and path-length dependence of jet energy loss due to quenching. We report measurements of the inclusive charged-particle jet yield in central Pb--Pb collisions, with the large uncorrelated background mitigated using a novel event mixing technique. This...
Viscous hydrodynamics serves as a successful mesoscopic description of the QGP produced in relativistic heavy-ion collisions. In order to investigate, how such an effective description emerges from the underlying microscopic dynamics we calculate the non-hydrodynamic and hydrodynamic modes of linear response in the sound channel from a first-principle calculation in kinetic theory. We do this...
Measurements in pp and p--Pb collisions, so-called small systems, besides serving as baseline for studying vacuum production and cold-nuclear matter effects, respectively, have recently shown intriguing features. In particular, measurements in high-multiplicity events have revealed striking similarities with heavy-ion collisions, where the formation of a quark-gluon plasma is expected. One of...
sPHENIX is a new collider detector at RHIC designed for pioneering studies of the Quark-Gluon Plasma with high-p$_T$ jet and heavy flavor probes. The jet physics program particularly relies on the sPHENIX calorimeter system, which consists of large-acceptance, hermetic electromagnetic and hadronic sections designed for high-resolution measurements of photons, electrons, hadrons, and jets....
Hadronic resonances have typical lifetimes that are comparable to that of the hadron gas phase created in the late stages of high-energy nuclear collisions. Therefore, a significant fraction of resonances decays inside a high-density medium and their decay daughters may rescatter with other hadrons destroying their initial kinematic correlations. A competing effect is resonance regeneration...
The differences in hadron chemistry observed at e+e- machines versus hadron
colliders may indicate that the mechanisms by which partons evolve into visi-
ble matter are not universal. In particular, the presence of many other quarks
produced in the underlying event may affect the hadronization process. With
full particle ID, precision vertexing, and a high rate DAQ, the LHCb detector
is...
We report the first direct evidence of thermalization of the Quark-Gluon Plasma (QGP) formed in ultra-relativistic heavy-ion collision, by studying the fluctuation of mean transverse momentum per particle ($\langle p_t \rangle$) in ultra-central Pb+Pb collision. The recent experimental data from the ATLAS collaboration at the Large Hadron Collider (LHC), provides measurement of variance of...
This talk presents a measurement of longitudinal decorrelation in $pp$ collisions with ATLAS. The deposited energy in the transverse $(x,y)$ plane is expected to vary, depending on the longitudinal $(z)$ slice examined, which is correlated with the rapidity of the produced particles. Thus, particles from different rapidity slices will have flow vectors that differ in magnitude and orientation...
Modifications of quarkonia production in hadronic collisions provide an im-
portant experimental observable that sheds light on the heavy quark interaction
with the nuclear medium. In small collision systems, quarkonia can suffer from
a combination of initial and final state effects such as shadowing and comover
breakup, and possible effects from a deconfined medium. The excited...
We consider non-equilibrium evolution of non-Gaussian fluctuations crucial for the QCD critical point search in heavy-ion collision experiments. We rely on the hierarchy of relaxation time scales, which emerges in the hydrodynamic regime near the critical point. We focus on the slowest modes which are responsible for observable signatures of the critical point. We derive evolution equations...
Measurements of light flavour particle production in small collision systems at the LHC energies have shown the onset of features (e.g. radial flow) that resemble what is typically observed in nucleus-nucleus collisions and attributed to the formation of a strongly interacting medium.
By performing more differential studies and analysing smaller fractions of the visible cross section the...
Particle correlations are a powerful tool to study the properties of the bulk nu-
clear matter produced in relativistic heavy ion collisions. The momentum cor-
relations between identical particles originating from the same particle-emitting
source, referred to as the Bose-Einstein correlations, measure scales that are
related to the geometrical size of the source. The two-particle...
Deciphering the process of hadronization has long been a formidable challenge, in part due to its non-perturbative nature. Over the years, various phenomenological models have emerged, all attempting to unravel the complexity of hadron production. Despite their different theoretical foundations, many of these models successfully account for the average yield of hadrons. This has spurred the...
The proper treatment of hadronic resonances plays an important role for many aspects of heavy ion collisions. We expect this to be the case also for hadronization, due to the large degeneracies of excited states, and the abundant production of hadrons from their decays. We show how a comprehensive treatment of excited meson states can be incorporated into quark recombination, and in extension,...
Major high-energy nuclear and particle experiments are challenged by the processing of large volumes of high precision data generated by sophisticated detectors in high-rate collisions, e.g., experiments at RHIC and LHC. To address this challenge, state-of-the-art real-time AI technology is being developed using modern deep neural networks and AI-centric hardware innovations. Supported by the...
Photonuclear reactions are induced by the strong electromagnetic field generated by ultrarelativistic heavy-ion collisions. These processes have been extensively studied in ultraperipheral collisions, in which the impact parameter is larger than twice the nuclear radius. In recent years, the observation of coherent J/$\psi$ photoproduction has been claimed in nucleus--nucleus (A--A) collisions...
Heavy quarks, i.e. charm and beauty, are produced at the initial stage of heavy-ion collisions, on a time scale shorter than the medium formation time, and are sensitive to the large initial magnetic field produced perpendicular to the reaction plane (defined by the impact parameter direction and beam direction) in non-central heavy-ion collisions. In the presence of a large initial magnetic...
High-energy jets are produced by the fragmentation of partons (quarks and gluons) that underwent hard scattering in the early stages of a collision. For quite a number of years, jets have been successfully used to probe the properties of the special form of matter, the quark gluon plasma (QGP), formed in high-energy heavy ion collisions. One of the most recognized signatures of the QGP, the...
Unpolarized protons can generate transversely polarized quarks or linearly polarized gluons through a distribution known as the Boer-Mulders' function. The fragmentation of similarly polarized partons to unpolarized hadrons is called the Collins' function. Both of these functions include correlations between the spin or polarization and the relative transverse momentum of the incoming parton...
We study the hydrodynamization process in the aftermath of ultrarelativistic heavy-ion collisions using effective kinetic theory simulations and different observables. For the pressure ratio $P_T/P_L$, we observe that its late-time evolution becomes universal in units of the kinetic relaxation time for sufficiently large couplings signaling the onset of a hydrodynamical attractor. In contrast,...
While the formation of the quark--gluon plasma (QGP) in heavy-ion collisions has been confirmed by characteristic patterns of flow measurements, it remains unclear what is the smallest possible collision system that can generate a similar medium exhibiting partonic collectivity. In this talk, we will present the new preliminary results of anisotropic flow in pp, p--Pb, and Pb--Pb collisions...
This talk will present the Bayesian inference approach for quantitatively characterizing the 3D dynamics of heavy-ion collisions and the Quark-Gluon Plasma (QGP) properties in the RHIC Beam Energy Scan (BES) program. To model the dynamics of the collisions from 7.7 to 200 GeV, we employ a (3+1)D dynamical initialization model coupled with the relativistic viscous hydrodynamics + hadronic...
Incoherent J/$\psi$ photoproduction is sensitive to fluctuations of the gluonic structure of the target. Thus, the measurement of $\rm{J/\psi}$ photoproduction off the colliding hadron sheds light on the initial state of QCD and provides important constraints on the initial conditions used in hydrodynamical models of heavy ion collisions. In this talk, we present the first measurement of the...
Photons provide snapshots of the evolution of relativistic heavy-ion collisions as they are emitted at all stages and do not interact with the medium strongly. Measurements of low momentum direct photons at PHENIX across different systems, from $p+p$, $p/d/^3$He$+$Au to Au$+$Au have been made possible due to the versatility of RHIC. An excess of direct photons, above prompt photon production...
The LHCb spectrometer has the unique capability to function as a fixed-
target experiment by injecting gas into the LHC beampipe while proton or ion
beams are circulating. The resulting beam+gas collisions cover an unexplored
energy range, intermediate to previous fixed-target experiments and the top
RHIC energy for AA collisions, and allow systems of different size to be stud-
ied. Here...
We study cold nuclear matter effects on Drell-Yan production at small and moderate $p_T$ in proton/pion-nucleus collisions using a new transverse-momentum dependent (TMD) factorization framework. Both collisional broadening and medium-induced radiative corrections in the initial state are considered in the soft-collinear effective theory with Glauber gluons (SCET$_{G}$) approach. We...
We study the boost-invariant non-conformal Boltzmann equation in the relaxation-time approximation using special moments of the distribution function and investigate how hydrodynamical behavior emerges as the plasma transits from the far-off-equilibrium free-streaming regime to the hydrodynamic regime. The infinite hierarchy of moments can be truncated by keeping only the three lowest moments...
Measurements of direct photons provide valuable information on the properties of the quark-gluon plasma (QGP) because they are colour-neutral and created during all phases of the collision. Sources of photons include initial hard scatterings, Bremsstrahlung and the fragmentation process, jet-medium interactions, and radiation from the medium.
Direct thermal photons, produced by the plasma,...
The JETSCAPE Collaboration reports new studies of jet transport in the QGP using Bayesian Inference, incorporating both hadron and jet inclusive yield suppression data, and jet substructure data. This analysis extends the previously published JETSCAPE Bayesian determination of $\hat{q}$, which was based solely on inclusive hadron suppression data.
JETSCAPE is a modular framework for...
Quantum Chromodynamics (QCD), the theory of strong interactions, predicts that at sufficiently high temperature and/or high energy density, normal nuclear matter converts into a deconfined state of quarks and gluons, known as the Quark-Gluon Plasma (QGP). To investigate the phase diagram of the QCD matter, the Relativistic Heavy Ion Collider (RHIC) started the first phase of the Beam Energy...
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...
One of the main challenges in the theory of heavy ion collisions is understanding how an initial state of two highly Lorentz-contracted nuclei acquires the features of a hydrodynamic plasma in a characteristic time of 1 fm/c. Arguably, the most successful descriptions of this out-of-equilibrium stage have been established by finding so-called “attractor” solutions in the various (simplified)...
We will present the final measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states (including $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S)) with the inclusive-charged particle yields. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV $pp$ collision data. A description of the technical...
Electromagnetic probes such as photons and dielectrons (e$^{+}$e$^{-}$ pairs) are a unique tool to study the space-time evolution of the hot and dense matter created in ultra-relativistic heavy-ion collisions. They are produced at all stages of the collision with negligible final-state interactions. At intermediate dielectron invariant mass ($m_{\rm ee} > 1$ GeV/$c^{2}$), thermal radiation...
We propose a method to find local plane wave solutions to linearized equations of motion of relativistic hydrodynamics in inhomogeneous backgrounds, i.e., when fluid is rigidly moving with nonzero thermal vorticity in equilibrium. Our method is based on extending the conserved currents to the tangent bundle, using Wigner transforms. The Wigner-transformed conserved currents can then be Fourier...
The LHCb detector’s forward geometry provides unprecedented access to
the very low regions of Bjorken x inside the nucleon. With full particle ID and
a fast DAQ, LHCb is able to fully reconstruct plentiful charged particles and
neutral mesons, as well as relatively rare probes such as heavy quarks, providing
a unique set of constraints on nucleon structure functions. This contribution...
Employing a dynamical initial state model coupled to (3+1)D viscous relativistic hydrodynamics, we explore the rapidity dependence of anisotropic flow in the Relativistic Heavy-Ion Collider (RHIC) small system scan at 200 GeV center of mass energy. We demonstrate that approximately 50% of the pT-differential triangular flow difference between the measurements by the STAR and PHENIX...
Determining the existence and the location of the QCD critical point remains a major goal in the heavy-ion collision experiments. A crucial theoretical input for achieving this goal is mapping the QCD equation of state in the presence of baryon chemical potential (mu) which at the moment is limited to small values of mu, away from the critical point. I present a new framework for...
Dielectrons emitted during the evolution of the hot and dense QCD medium created in relativistic heavy-ion collisions offer an effective way to probe the medium properties, as they do not interact via the strong force. The rate of the dielectron emission is proportional to the medium's electromagnetic spectral function. In the dielectron mass range from $400$ MeV/$c^{2}$ to $800$ MeV/$c^{2}$,...
We investigate whether early and late time attractors for non-conformal kinetic theories exist by computing the time-evolution of a large set of moments of the one-particle distribution function. For this purpose we make use of a previously obtained exact solution of the 0+1D boost-invariant massive Boltzmann equation in relaxation time approximation. We extend prior attractor studies of...
Relativistic heavy-ion beams at the LHC are accompanied by a large flux of equivalent photons, leading to multiple photon-induced processes. This talk presents a series of measurements of dilepton production from photon fusion performed by the ATLAS Collaboration. Recent measurements of exclusive dielectron production in ultra-peripheral collisions (UPC) are presented. These processes provide...
There is increasing interest in using high-energy collisions to probe the structure of nuclei, in particular with the high-precision data made possible by collisions performed with pairs of isobaric species. A systematic study requires a variation of parameters representing nuclear properties such as radius, skin thickness, angular deformation, and short-range correlations, to determine the...
Two-particle correlations are presented for $\mathrm{K^{0}_S}$, $\Lambda$, and $\bar{\Lambda}$ strange hadrons as a function of relative momentum in lead-lead (PbPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV with data samples collected by the CMS experiment. These correlations are sensitive to quantum statistics and to final-state interactions between particles. The...
Recent measurements of the production of charm hadrons at midrapidity in pp collisions at $\sqrt s$ = 5.02 and 13 TeV showed that the baryon-to-meson yield ratios are significantly larger than those measured in $\rm e^{+}e^{-}$ collisions for different charm-baryon species. These observations suggest that the charm fragmentation fractions are not universal and that the baryon-to-meson ratios...
Two-particle correlations are used to extract the space-time and dynamical information of the particle-emitting source created in heavy-ion collisions. The source radii extracted from these correlations characterize the system at the kinetic freeze-out, i.e., the last stage of particle interactions. Kaons can provide a more direct view of the particle-emitting source than pions as they have...
The Electron-Ion Collider (EIC) at Brookhaven National Laboratory will be an experimental facility to explore gluons in nucleons and nuclei, shedding light on their structure and the interactions within. The ePIC detector will be the first experiment at the EIC dedicated to detailed studies of nuclear structure in electron-proton and electron-ion collisions.
The ambitious physics program of...
In this contribution, we extend the scope of the JETSCAPE framework to cover the jet radius ($R$) dependence of the jet nuclear modification factor, ${R_{AA}}$, for broader area jet cones, going all the way up to $R$ = 1.0. The primary focus of this work has been the in-depth analysis of the high-${p_{T}}$ inclusive jets and the quenching effects observed in the quark-gluon plasma formed in...
Electromagnetic radiation is emitted throughout the whole evolution of high-energy heavy-ion collisions. Due to their penetrating nature, real and virtual photons reach the detector unimpeded. Their measurement makes it possible to shed light on the different stages of the extreme states of matter created in such collisions.
In this poster, we will discuss dielectron measurements that will...
We demonstrate that the early stages of the bottom-up thermalization scenario [1] are well described by the adiabatic hydrodynamization framework, thus providing novel analytic results on the thermalization process of QCD in a heavy ion collision. These results provide an intuitive explanation of why a gas of quarks and gluons can relax so quickly towards equilibrium, and provide a starting...
The production of deuterons in pp collisions at $\sqrt{s}=$ 13 TeV is simulated on an event-by-event basis using a coalescence afterburner based on a state-of-the-art Wigner-function formalism, and EPOS 3 and PYTHIA 8.3 as event generators. The space-momentum correlations of the nucleon pairs provided by the event generators are preserved, while the nucleon-emitting source is modelled such to...
Hypernuclei are bound states of nucleons and hyperons. The study of their properties, such as their lifetimes and binding energies, provide information on the hadronic interaction between hyperons and nucleons which are complementary to those obtained from correlation measurements. Precise modeling of this interaction is a fundamental input for the calculation of the equation of state of...
The spin alignment of vector mesons emitted in heavy-ion collisions has recently been measured by the ALICE and STAR collaborations over a wide range of energies [1, 2]. The alignment is part of the so-called tensor polarization, which is a property that is exclusive to particles of spin 1 and higher. Even though there have been substantial theoretical efforts, a definite explanation for the...
The quark-hadron transition that happens in ultra-relativistic heavy-ion collisions is expected to be influenced by the effects of rotation and magnetic field, both present due to the geometry of a generic non-head-on impact. We augment the conventional $ T$--$\mu_B$ planar phase diagram for QCD matter by extending it to a multi-dimensional domain spanned by temperature $T$, baryon chemical...
We present an innovative procedure to account for unavoidable contributions from volume (or system size) fluctuations to experimentally measured cumulants of particle multiplicity distributions produced in relativistic nuclear collisions. For the first time we extract participant fluctuations directly from the data used for the fluctuation analysis, i.e., without involving model calculations...
Isobar collisions, $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr, at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV have been performed at RHIC. These collisions are considered to be an effective way to minimize the flow-driven background contribution to search for the possibly small CME signal. Anisotropic flow is an important tool to understand properties of the QGP medium. Elliptic...
Multiple evidence reveals that the vast majority of the matter content of the universe is non baryonic and electrically neutral. This component is usually called Dark Matter (DM), for its lack of electromagnetic interactions, and is measured to constitute about 25% of the energy density of the Universe. The most common hypothesis is that it consists of weakly interacting massive particles,...
The long-range ($|\Delta\eta| \gt 2$) near-side ($\Delta\phi\approx0$) ridge structure in a two-particle correlation analysis has been observed in heavy ion collision, which was well-explained by the hydrodynamic models based on the quark-gluon plasma (QGP) effect. However, even though small systems such as pp and pPb collisions cannot have enough density and temperature to create the QGP...
Heavy-flavor (charm and beauty) quarks are generated primarily via hard scattering processes in high-energy hadronic collisions, and then undergo parton shower (fragmentation) and hadronization. Two-particle azimuthal correlations of heavy-flavor particles is a differential measurement which allows for the study of the fragmentation of heavy quarks. By measuring the azimuthal correlation in...
The beauty quark is a unique probe to study the properties of quark-gluon plasma thanks to its large mass and relatively long thermal relaxation time compared with lighter partons. Traditional experimental observables such as elliptic flow v$_2$ and nuclear modification factor R$_{AA}$ of fully reconstructed beauty hadrons have been measured at the LHC. Moreover, indirect measurements on...
Beauty quarks are produced in hard-parton scatterings in the early stages of the partonic collisions. They are the ideal probe to investigate the properties of Quark-Gluon Plasma (QGP) produced in ultra-relativistic heavy-ion collisions as they experience the whole QGP evolution. Due to their large mass, their production can be calculated using perturbative Quantum Chromodynamics (pQCD), thus...
In ultra-relativistic heavy-ion collisions, the colliding nuclei are decelerated and kinetic energy is converted into new particles. This energy loss is referred to as baryon stopping. A fundamental question one can ask in the study of high energy heavy-ion collisions is how much baryon stopping there is. This can be quantified by measuring the net proton rapidity distributions. Previous...
Fluctuations of conserved quantities are proposed as a powerful observable to search for the QCD critical point. Recently, proton cumulants from central Au+Au $\sqrt{s_{NN}}$ = 3 GeV collisions were reported, which implies that hadronic interactions are dominant at 3 GeV and the QCD critical point could exist at the collision energies higher than 3 GeV. The baryon-strangeness correlation is...
The sPHENIX TPC readout will use an array of quadruple-stacked gas electron multiplier (GEM) modules to amplify signals from the chamber in order to perform precise tracking measurements. The performance of the system may be affected by a shift in the readout baseline due to event-by-event fluctuations. These fluctuations are a result of the common-mode noise generated in the induction gap of...
Ultra-relativistic heavy-ion collisions at RHIC are thought to have created a Quark-Gluon-Plasma (QGP) with a very low shear viscosity in the deconfined phase. However, as the QGP hadronizes it will evolve through a hadronic phase with rapidly increasing shear viscosity. In order to fully characterize the QGP state, one has to separately determine the viscosity of the hadronic phase. Although...
High-energy heavy-ion collisions offer a unique and precise way to probe nuclear structures by providing a snapshot of the nuclear distribution at the time of the collision, which is complementary to low-energy nuclear physics experiments.
In this talk, we present a comprehensive scan of flow observables, including anisotropic flow coefficients, nonlinear flow modes, and normalized...
The sPHENIX Time Projection Chamber (TPC) is a gaseous drift detector
designed to measure charged particle tracks. It is filled with Argon/CF4 and uses
Gaseous Electron Multiplier (GEM) foils at readout for electron amplification
and ion back-flow suppression. The electrons at readout are measured, converted
to digital current, and their signal waveforms are processed to reconstruct the...
The Time Projection Chamber (TPC) is the main tracking detector in sPHENIX. Charged particles which pass through the TPC ionize the gas, with the transverse position being given by the readout pad and the time for the ionization electrons to drift to the endcaps defining the z position. The ionization electrons are clustered together in order to track particles and determine their momenta. In...
The sPHENIX Time Projection Chamber (TPC) serves as the main tracking detector of the sPHENIX experiment, which began operating at the Relativistic Heavy Ion Collider at Brookhaven National Lab this year. It operates with a quadruple-GEM avalanche stage which provides gain while restricting the flow of ions back into the chamber sufficiently to operate in streaming mode, without any...
The multiplicity distribution measures the probability of obtaining a certain number of particles in a given collision and is one of the first observables measured in data at each new collision type and center of mass energy. It is relevant since is one of the fundamental observables to describe the global properties of the interactions and is sensitive to non-linear QCD evolution in the...
Multiplicity distributions of primary charged particles are sensitive to non-linear QCD evolution in the initial state. We present the distributions in various pseudorapidity ranges in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV. Charged particles are reconstructed using the Inner Tracking System that has been upgraded for Run3 at LHC and is operation starting in 2022. The data are...
sPHENIX, the first detector to be built at the Relativistic Heavy-Ion Collider (RHIC) in over two decades, will bring unprecedented measurement capabilities at RHIC energies. One of the initial physics measurements to be performed by sPHENIX concerns the charged-particle multiplicity, which utilizes the tracklet analysis method with the cluster information from the...
We study the production of charm quarks in hot QCD medium described by quasiparticle excitations of quarks and gluons. The effective masses are adjusted through the coupling to satisfy the entropy density obtained on the lattice [1]. The evolution of the QGP is described by hydrodynamic simulations in (2+1) dimensions with temperature-dependent shear viscosity taken into account [1,2]. The...
Quarkonium production is considered one of the golden probes of the quark-gluon plasma (QGP) formation in heavy-ion collisions.
Due to their large mass, the production of heavy-quarks is governed by hard scales of QCD, while the formation of the bound quarkonium state involves soft QCD scales.
The regeneration process of J/$\psi$ in the QGP or at the phase boundary is crucial for describing...
The AdS/CFT correspondence, which connects strongly coupled conformal field theories in $N$ dimensions to gravity in $N+1$ dimensional Anti-de Sitter space, has provided valuable insights into the non-perturbative aspects of QCD. Soft-wall AdS/QCD is a phenomenological model that uses a dilaton field to introduce confinement, while a scalar field is dual to the chiral condensate. The...
Balance functions have been extensively used to elucidate the time evolution of quark production in heavy-ion collisions. Early models predicted two stages in the quark production, one for light quarks and one for the slightly heavier strange quark, separated by a period of isentropic expansion. This led to the notion of clocking the particle production and tracking radial flow effects. The...
Many physics observables of interest in heavy-ion collisions require knowledge of the collision geometry. Geometric fluctuations lead to different symmetry planes of the initial geometry for each harmonic number, called participant planes. As the produced medium evolves, pressure gradients transform the initial state spatial anisotropy into final state momentum anisotropy. The angular...
We present a relativistic density functional approach to color superconducting quark matter that mimics quark confinement by a fast growth of the quasiparticle self-energy in the confining region [1]. The approach is shown to be equivalent to a chiral model of quark matter with medium dependent couplings. The approach to the conformal limit at asymptotically high densities is provided by a...
The new sPHENIX detector at RHIC will begin commissioning with Au+Au collisions at 200 GeV in Spring 2023, followed by p+p and p+Au data taking in 2024. The experiment combines triggered readout of the calorimeter system with streaming readout of the tracking detectors in a hybrid readout scheme. The hybrid readout scheme enables a large increase in the collected statistics in particular for...
Net-charge, net-strangeness and net-baryon number fluctuations measured in ultra-relativistic heavy-ion collisions may reveal details and insights into the quark-hadron transition, hadro-chemical freeze-out and possibly aid in the search of the QCD critical point. By controlling the collision energy, some current and upcoming heavy-ion facilities aim to study high energy nucleus-nucleus...
Constructed at Lehigh University between 2021 and 2023, the sPHENIX Event Plane Detector (sEPD) will measure charged particle multiplicity at forward rapidity from the collision of hadrons. This detector consists of 24 triangular sectors, each of which is divided into 31 optically isolated tiles of plastic scintillating material, such that light can be collected from a discrete area of the...
HADES has a large acceptance as well as excellent particle identification capabilities and therefore allows the study of dielectron, hadron, and light nuclei production in heavy-ion collisions with great precision. The harmonic flow coefficients $v_n$ of the order $n = 1 − 6$ are measured with HADES as a function of centrality, transverse momentum, and rapidity in Au+Au collisions at 1.23...
Correlations involving the seven conserved quantities, $\{E,\vec{p},Q,S,B\}$, were modeled for heay-ion collisions at finite baryon density. The evolution of correlations as a function of relative rapidity was treated as a linear response to local thermodynamic fluctuations of on the Bjorken-model background. The entire 7x7 matrix of correlations was found to be significant, sensetive to the...
Correlations between net-conserved quantities such as net-baryon, net-charge and net-strangeness are essential probes of QCD phase structure and are related to the ratios of thermodynamic susceptibilities in lattice QCD calculations. The study of these correlations can probe thermal conditions in a medium and help to elucidate the nature of the strongly interacting matter formed in high-energy...
Studies of charm production in proton-proton ($pp$) collisions are essential to understand some of the most fundamental aspects of Quantum Chromodynamics. They also provide the baseline for interpretation of charm data from larger colliding systems. Over the last decade, the measurement of the production cross-sections of charm mesons and baryons in $pp$ collisions has been at the centre of a...
In this poster, PHENIX presents a proof of principle study for the measurement of prompt and non-prompt $e^{+}e^{-}$ pair production in the intermediate mass range ($m_{\phi}$ $<$ $m_{ee}$ $<$ $m_{J/\psi}$) using $p$+$p$ data at 200 GeV taken in 2015. PHENIX plans to extend the measurement to the high statistics Au+Au data-set recorded in 2014 and 2016, with the goal to isolate the expected...
Results from heavy-ion collisions confirmed the scenario in which the deconfined state of nuclear matter, dubbed the quark--gluon plasma (QGP), undergoes a collective expansion. Collective anisotropic flow, quantified with Fourier harmonics of azimuthal distribution of particles, $v_n$, is one of the most sensitive experimental probes to constrain QGP properties. Recently developed...
In this contribution we present results on the dielectron production in $Ag+Ag$ collisions (0-40% centrality) and $p+p$ interactions at $1.58 \, AGeV$ beam energy measured with the High Acceptance DiElectron Spectrometer (HADES). The HADES RICH detector has been upgraded with a new photon detection camera which strongly enhances the electron efficiency and...
The anisotropic flow parameters $(v_{n})$ offer insights into collective hydrodynamic expansion and transport properties of the produced medium at higher collision energies, while they are sensitive to the compressibility of the nuclear matter and nuclear equation of state at lower collision energies. Among them directed flow ($v_1$) describes the collective sideward motion of produced...
Studying hyper-nuclei production and their collectivity can shed light on their production mechanism as well as the hyperon-nucleon interactions under finite pressure. This is a unique opportunity for heavy-ion collisions at high baryon density region where hypernuclei production rate increases.
In this poster, we will present $v_{1}$ of the hyper-nuclei ($\Lambda$, $^{3}_{\Lambda}{\rm...
Directed flow of particles is an important feature seen in heavy-ion collisions and is a sensitive probe to the equation of state (EoS) of the matter produced in the collisions. Model calculations have also predicted that directed flow could be sensitive to the softening of EoS associated with a first order phase transition. Directed flow of protons and anti-protons are also of interest as...
The Time Projection Chamber (TPC) to be used for tracking and particle identification in the sPHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) is expected to experience significant distortions from build-up of backflowing ions created by the combination of high collision rates and amplification from Gas Electron Multiplier (GEM). By integrating the digitized readout from the...
The nuclear modification factor related to the Drell-Yan (DY) production cross-section is an excellent probe of the cold nuclear matter (CNM) properties. The acceptance of the sPHENIX detector allows detection of DY events in the dielectron channel for p$_\perp$ ≳ M, where p$_\perp$ is the dilepton transverse momentum and M its invariant mass. In this kinematic region, the DY cross-section is...
In the chiral limit the complicated many-body dynamics around the second-order chiral phase transition of two-flavour QCD can be understood by appealing to universality. We present a novel formulation of real-time functional renormalization group that describes the stochastic hydrodynamic equations of motion for systems in the same dynamic universality class, which correspond to Model G in the...
We analyze the effect of hydrodynamic fluctuations on normalized mixed harmonic cumulants ($nMHC$) [1,2] for the first time based on event-by-event simulations of high-energy heavy-ion collisions using an integrated model of an initial state model, stochastic causal fluctuating hydrodynamics, and a hadronic afterburner.
For the quantitative constraints on the transport properties of...
In heavy ion collisions, the initial state geometry plays a crucial role in determining final state observables such as elliptic flow $v_2$ and radial flow reflected by event-wise average transverse momentum $[p_{\rm T}]$. The initial state geometry is influenced by several nuclear shape parameters, including quadrupole deformation (β), triaxiality (γ) [1], nuclear radius (r), and skin depth...
Jets are excellent probes for studying the deconfined matter formed in heavy ion collisions. However, competing energy-loss effects, such as the dependence on the opening angle of the shower, radiative emissions to large angles, and the medium response to the jet, can obscure interpretation. This talk presents two new observables aimed at disentangling these effects. First, we introduce a new...
Chiral media, such as quark-gluon plasma, possess a number of unique properties originating from the quantum phenomenon of the chiral anomaly. These properties can be measured by observing the propagation of fast charged particles moving through the medium and the radiation produced in the process. We show how the chiral anomaly confers distinctive features onto the particle energy loss and...
Energy-energy correlators (EEC) offer a novel way to study the structure of jets. Defined as the energy-weighted cross section of particle pairs inside jets, the correlation strength as a function of the pair opening angle allows a distinct separation of the perturbative and non-perturbative regimes. The evolution of parton dynamics in jets to their confinement into hadrons can be studied....
Energy-energy correlators (EEC) have been proposed to study the structure of energy flow within jets. These functions are defined as the energy-weighted cross-section of particle pairs inside jets. The correlation as a function of pair distance and jet transverse momentum offers a clear separation between the perturbative and non-perturbative regimes, where one can probe the dynamics of quarks...
In an effort to better understand the thermal-like behavior and particle yields seen in p-p collisions we recast the problem employing the principles of quantum states and their entanglement in the produced system. We seek to show that this entanglement in the initial state has a measurable effect on the evolution of the system and is the driving mechanism behind the thermal-like behavior and...
Multiplicity data on $\rm\bar{p}$p/pp collisions at {\footnotesize SPS} and {\footnotesize LHC} energies (0.2-7 TeV) are used to study the entropy production, dimensions and other multifractal characteristics of multiplicity distributions of relativistic charged particles produced. It is observed that the entropy produced in smaller and(or) larger phase space bins, when normalized to maximum...
Measurements of azimuthal correlations of charmed mesons in high-energy heavy-ion collisions can shed light on the transport properties of the Qaurk-Gluon Plasma. The STAR experiment at the Relativistic Heavy Ion Collider (RHIC) collected in 2014 and 2016 a large sample of Au+Au reactions at $\sqrt{s_{NN}}$ = 200 GeV making such a study possible. The sPHENIX experiment will also offer a...
A hot and dense system formed in heavy-ion collisions can be characterized by studying the scaling behavior of the spatial distributions of the produced particles. In this contribution, we present intermittency analysis of the normalized factorial moments ($F\rm{_{q}}$) of the multiplicity distributions of the charged particles produced in Pb--Pb collisions as a function of phase-space...
Hadronic resonances are interesting candidates to study the properties of the hadronic phase, which is the time span between the chemical and kinetic freeze-outs, formed during the evolution of relativistic heavy-ion collisions. Due to their short lifetimes, comparable to the lifetime of hadronic phase ($\sim$10 $-$ 12 fm/$c$), they decay in the hadronic phase and their decay products undergo...
The Chiral Mean Field model (CMF) has been successful in describing the equation of state at large baryon densities, such as those found in neutron stars, neutron star mergers, and heavy-ion collisions. The MUSES collaboration has rewritten the zero-temperature CMF model from Fortran 77 into a parallelized modern C++20 using OpenMP, which has resulted in at least an order of magnitude...
Heavy-ion collisions produce a quark-gluon plasma that undergoes rapid expansion and cooling, which presents a challenge for calculating jet quenching observables. Current approaches rely on analytical results for static cases, introducing theoretical uncertainties and biases in our understanding of the pre-equilibrated medium. To address this issue, we employ analytical re-summation schemes...
The thermal fluctuations in the QGP medium formed in heavy ion collisions present themselves as event-wise $[p_\mathrm{T}]$ fluctuations in the final state. Recent studies have shown that the average and higher-order fluctuations of $[p_\mathrm{T}]$ in ultra-central collisions are sensitive to radial flow, random thermal motion, and nuclear deformation, and can provide constraints on the...
Recent measurements in proton-proton (pp) and proton-lead (p--Pb) collisions have shown features that are reminiscent of those observed in lead-lead (Pb--Pb) collisions, such as near-side long-range correlations, mass-dependent hardening of ${p}_{\mathrm T}$ spectra, strangeness enhancement etc. Therefore, one of the key challenges today is understanding the origin of strangeness enhancement...
We investigate the characteristics of gluonic cascades in static and expanding media by numerically solving the complete BDIM (Blaizot-Dominguez-Iancu-Mehtar-Tani) evolution equations in longitudinal and transverse momentum using the Monte Carlo event generator MINCAS. In this analysis, we compare angular distributions of in-cone radiation across various medium profiles with effective scaling...
It is well established that the late states of a high energy nuclear collision can be described in terms of relativistic fluid dynamics. An open problem in this context is how the actual collision and the early time dynamics directly after it can be described. Phenomenological models are currently employed here and they have several parameters that need to be fitted to experimental...
The origin of hadron masses cannot be attributed to the Higgs mechanism alone. On top of that, the spontaneous breaking of chiral symmetry potentially restored at extremely high temperatures, plays an important role. Low-mass vector mesons (ρ, ω, φ) are highly sensitive to chiral symmetry restoration effects, and their electromagnetic spectral function is expected to be modified in Pb-Pb...
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 experiments, femtoscopic (momentum) correlations are utilized to gain information about the space-time geometry of the particle emitting source....
NA61/SHINE has measured the first deuteron production in proton-proton interactions at 158 GeV/c (sqrt(s) = 17.3 GeV). These measurements will be presented and compared to different nuclear formation models. The two most prevalent formation models—the thermal and coalescence models—are based on different underlying physics. A better understanding of (anti)nuclei production mechanisms is...
Besides the traditional flow studies of individual flow amplitudes $v_n$, independent information about all stages in heavy-ion evolution can be extracted from multi-harmonic correlations of flow amplitudes. The simplest realization is Symmetric Cumulants (SC), which correlate the same-order moments of two or more flow amplitudes. In recent studies, it was demonstrated that SC can reveal the...
Accurate knowledge of the strong interaction between charged kaons and (anti)deuteron is a missing piece of information in the field of the low-energy (anti)kaon-nucleon interactions for more than 40 years. The interaction between charged kaons and (anti)deuterons is a complex subject at both experimental and theoretical levels. From the experimental point of view, so far scattering cross...
The first results on identified hadron spectra produced in central Xe+La collisions at SPS will be presented. The kinematic distributions and measured multiplicities of identified hadrons will be compared with previously released by NA61/SHINE results on p+p, Be+Be, Ar+Sc and NA49 Pb+Pb results, as well as with available world data.
Obtained results, and in particular ratio of positively...
Higher order flow harmonics provide a powerful probe of the initial geometry of heavy ion collisions, as well as the properties of the quark-gluon plasma produced in these collisions, including the transport coefficients and the degree of collective behavior. This poster presents higher order flow harmonics measurements in PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$~TeV using data...
Forward and backward rapidity regions are rich laboratories to explore several effects which happens to a probe before and after its hard scattering. The large rapidity region may also experiment a different dynamics for strangeness enhancement seen in heavy ion collisions at RHIC and LHC. The PHENIX experiment has a long history of large rapidity measurements with the muon spectrometers...
Various interesting phenomena have been predicted to occur in a quark-gluon plasma produced in relativistic heavy-ion collisions due to a strong magnetic field which is also generated in these collisions. However, none of these predictions has been convincingly confirmed experimentally yet. So, the question is why? Our aim is to systematically discuss the problem of magnetic field generation....
The sPHENIX experiment at RHIC will begin commissioning with Au+Au data in Spring 2023. The Monolithic Active Pixel Sensor (MAPS) based Vertex Detector (MVTX), the Intermediate Silicon Tracker (INTT) and the Time Projection Chamber (TPC) at sPHENIX can provide high precision primary/displaced vertex and track reconstruction in the pseudorapidity region of $|\eta| \le 1.1$. The sPHENIX...
Heavy quarks serve as effective probes of relativistic heavy-ion collisions as they are created in the initial stages of the collision event and exist at all stages. We study the dynamics of heavy flavors using a hybrid framework that incorporates the MARTINI event generator, pythia8.1 for the initial production of heavy quarks, and Langevin dynamics to describe the evolution of heavy quarks...
The sPHENIX experiment will begin commissioning in Spring 2023 at the Relativistic Heavy Ion Collider (RHIC) at BNL, presenting a unique opportunity to study QGP properties using jets and heavy quarks with unprecedented precision. The successful construction and deployment of the three-layer Monolithic-Active-Pixel-Sensor (MAPS) based VerTeX detector (MVTX) for the sPHENIX experiment in 2023...
The early stage of high-energy nuclear collisions is dominated by strong gluon fields called the evolving Glasma. This stage can be probed by heavy quarks (HQs), charm and beauty, since they are produced almost immediately by hard scatterings. We study the propagation of HQs in the evolving Glasma fields, by solving the relativistic kinetic equations that couple the HQs to the fields...
Owing to its spectrometer acceptance, which is complementary to the other
LHC experiments, LHCb is collecting several fixed-target and ion collision sam-
ples, providing unique inputs to theoretical models in poorly explored kinematic
regions. In this contribution, the impact of the ongoing and foreseen upgrades
of the LHCb experiment on the ions and fixed-target physics programme...
Relativistic hydrodynamics has been successful in describing space-time evolution of matter created in high-energy nuclear collisions. It is conventionally supposed that the created matter starts to behave as fluids all at once at a certain initial time. It is, however, not at all trivial from which stage after the collision the fluid picture can be applied to the system. According to the...
Reconstructing hyperons with high purity and high reconstruction efficiency is essential for measurements of hyperon-hyperon correlation and searches for exotic strange hadrons, which are both presently discussed topics in the QCD community. Hyperons can be abundantly produced in Pb-Pb collisions at LHC. However, achieving high purity of reconstructed hyperons with high efficiency is...
Hypernuclei, bound states of nucleons and hyperons, serve as a natural laboratory to investigate the hyperon-nucleon ($Y$-$N$) interaction, which is an important ingredient for the nuclear equation-of-state. Furthermore, precise measurements of their production yields in heavy-ion collisions are crucial for understanding their production mechanisms. In addition, the strangeness population...
Antimatter in cosmic rays is a powerful probe for Dark Matter indirect de-
tection. To constrain the background from secondary antiparticles, produced
during cosmic ray propagation through the interstellar medium, the related cross
sections need to be precisely determined at accelerator facilities. In particular,
being their secondary production suppressed at low energies with respect...
Measurements of jet substructure in ultra-relativistic heavy ion collisions suggest that the jet showering process is modified by the interaction with quark gluon plasma. Modifications of the hard substructure of jets can be explored with modern data-driven techniques. In this study, we use a machine learning approach to identify jet quenching amounts. Jet showering processes, with and without...
The collective properties of nuclear structure, such as radii and deformations, leave distinct signatures in the initial and consequently final stages of relativistic heavy-ion collisions. Collisions of deformed nuclear enhance the fluctuations of harmonic flow coefficients $v_n$ and event-wise mean transverse momentum $[p_T]$, therefore offering a viable approach to establish clear...
The study of small collision systems at RHIC (pp, pA, dA, $^{3}$HeA, OO) and the LHC (pp, pPb, OO) provide crucial insights into the limits of quark-gluon plasma formation. Recently, we have analyzed new experimental results in terms of hydrodynamics, pre-hydrodynamics, decorrelations, and non-flow (Phys.Rev.C 105 (2022) 2, 024906). We extend these studies to include ultra-peripheral...
Previous applications of machine learning to jet background subtraction have shown improvements over the traditional background subtraction methods, especially at low jet momentum. While machine learning applications generally lead to improvements, care must be taken to ensure they are not at the cost of interpretability and bias from models used for training. We present a novel application of...
Heavy-quark hadrons are used to study the properties of the partonic stages of a heavy-ion collision, where a quark-gluon plasma medium is created. We are investigating charm quark production in and outside of jets via angular correlations of trigger hadrons and associated electrons from heavy-flavor hadron decays. As a first step, we are investigating the 5.02 TeV p-Pb collisions, where in a...
Studies have yielded strong evidence that a deconfined state of quarks and gluons, the quark--gluon plasma, is created in heavy-ion collisions. This hot and dense matter exhibits almost zero friction and a strong collective behavior. An unexpected collective behavior has also been observed in small collision systems. In this talk, the origin of collectivity in small collision systems is...
Jet quenching measurements in heavy-ion collisions, such as the suppression of the jet yield compared to pp collisions, aim to elucidate the various mechanisms of parton energy loss. Differential measurements of the dependence of the inclusive jet nuclear modification factor ($R_{\rm AA}$) on the jet resolution parameter ($R$) may help disentangle energy loss mechanisms and discriminate...
In this poster, we present the ATLAS measurement of the centrality dependence of the dijet per-event yield at center-of-mass energy 8.16 TeV in $p$+Pb collisions. The per-event yield of unfolded dijet pairs is presented in terms of kinematic variables that allow for full characterization of the partonic scattering system, i.e. the average $p_{\mathrm{T}}$ of the dijet, $p_{\mathrm{T,Avg}} =...
High-energy nucleus-nucleus collision experiments have played a crucial role in exploring high-temperature quark matter, such as the quark-gluon plasma (QGP). The study of various hadrons, characterized by diverse internal structures, constituent quark numbers, and quark species, has been essential for understanding QGP properties. It has become increasingly evident that hadron yields in...
The sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC) is designed to study the small scale structure of the quark-gluon plasma (QGP) created in collisions of heavy ions. Jets, produced in hard scatterings early in the collisions, provide an ideal probe for the full evolution of the QGP. sPHENIX is the first detector at RHIC with full coverage electromagnetic and hadronic...
The jet quenching parameter $\hat q$ encodes jet medium interactions during the entire quark-gluon plasma evolution in heavy-ion collisions. For a long time, the impact of pre-equilibrium stages has not been properly treated in jet quenching calculations, although recent studies find large values for $\hat q$ in the earliest (glasma) stage. For the first time, we show that QCD kinetic theory...
The new sPHENIX detector at Brookhaven’s National Laboratory’s Relativistic Heavy Ion Collider (RHIC) was designed to significantly further the study of the nature of hot nuclear matter. The use of jets as a probe in p+A and A+A collisions allows access to the interaction of the hard-scattered partons with the nuclear environment and is sensitive to a wide range of scales. sPHENIX will use...
In high-energy nuclear collisions, the light nuclei production is sensitive to the temperature and density of the system at freeze-out. It is also predicted to be sensitive to local baryon density fluctuations and can be used to probe the QCD phase transition. The second phase of Beam Energy Scan (BES-II) program at RHIC was completed in 2021. The high-statistics data recorded by the STAR...
We present a Monte-Carlo implementation of the EKRT initial-state model (MC-EKRT) [1]. Our new MC-EKRT event generator is based on collinearly factorized, dynamically fluctuating pQCD minijet production, supplemented with a saturation conjecture that controls the low-$p_T$ particle production. Previously, the EKRT model has been very successful in describing low-$p_T$ observables at...
The mean $p_{\rm{T}}$ fluctuations in heavy-ion collisions can be related to temperature fluctuations which quantify the specific heat of the system. Any deviations from the Hadron Resonance Gas model as a function of the incident energy can be interpreted as a possible signal of criticality. In this poster we present the first efficiency corrected charged particle event-by-event mean...
Measurements of the production of heavy-flavour hadrons in proton–proton (pp) collisions provide an important test of quantum chromodynamics (QCD).The heavy-flavour production cross section can be calculated using the factorisation approach as a convolution of three factors: the parton distribution functions, the partonic cross section, calculated with perturbative QCD calculations, and the...
Measurements of charm baryon and meson production in pp and p–Pb minimum bias collisions and as a function of multiplicity, help to investigate hadronization processes and to study their modification across the collision systems from pp to Pb–Pb, and from low to high multiplicities.
Recent measurements of the fragmentation fractions of charm hadrons in pp and p–Pb challenge the universality...
Heavy quarks are produced at the very early stage of heavy-ion collisions, and they experience the whole evolution of the Quark-Gluon Plasma (QGP) created in these collisions. Measurements of the elliptic flow and nuclear modification factor of charmed mesons in heavy-ion collisions at RHIC and the LHC provide ample evidence of strong interactions between charm quarks and the QGP. However, a...
By comparing the particle production in pp and p--Pb collisions, nuclear initial state effects can be studied. Measurements of the $\omega$ meson $p_\text{T}$-spectra in pp and p--Pb collisions not only allow for a determination of the nuclear modification factor $R_\text{pA}$, but also provide insight into the fragmentation process and serve as vital input for direct-photon cocktail...
The properties of the Quark-Gluon Plasma (QGP) produced in heavy-ion collisions can be studied using jets generated in hard scattering processes at the early stages of the collision. These jets lose energy and have their shower structures modified relative to that in the vacuum due to jet-medium interaction — known as `jet quenching'.
The transverse momentum ($p_{\rm T}$) fraction of the...
Compared to $\rm{e^+e^-}$ and ep collisions, the charm baryon production in pp collisions shows a substantial enhancement. This evidence is currently interpreted in terms of a modification of the hadronization mechanisms in hadronic collisions. Therefore, valuable information on how the charm quarks hadronize can be studied by measuring charm baryon production. In addition, by sorting out the...
$J/\psi$ serves as an important probe to study the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions. In Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}} = 200$ GeV, it has been observed that the $J/\psi$ yield is strongly suppressed and its elliptic flow ($v_{2}$) is consistent with zero, indicating $J/\psi$'s strong coupling with the medium and its potentially small...
Two-particle correlation analyses are often used to study the spatial and temporal extension of particle-emitting source in high-energy nuclear collisions. Precise information on the final state interactions amongst the particles under study can also be extracted from the measurement. It is particularly interesting to study the energy dependence of the extracted source size at the moment of...
Jets are collimated sprays of hadrons fragmented by highly virtual partons produced in the early stage of heavy-ion collisions via hard scatterings. Different observables of the jet-medium interaction probe the properties of the Quark-Gluon Plasma and its dynamics. The bulk medium produced in non-central heavy-ion collisions is expected to be tilted with respect to the beam axis, while the...
Studying heavy flavor can enhance our comprehension of parton interactions with the Quark-Gluon Plasma (QGP). Due to their significant mass, heavy quarks (charm and bottom) are mainly generated during the initial phase of high-energy heavy-ion collisions when hard scatterings are prevalent, and experience the entire evolution of the QGP. One way to study the production of heavy quarks is...
Particle production in ultra-relativistic pp collisions can be factorized into the parton density function (PDF), the partonic cross-section and the fragmentation function (FF). FFs need to be constrained by experimental data for each particle species. Measurements of the momentum fraction $z$ of a particle species contained in a high energetic jet give direct access to the FF of the...
The production of hadrons containing charm or beauty quarks in pp collisions provides an important test for quantum chromodynamics calculations. These measurements also serve as reference for more complex systems such as Pb--Pb collisions, helping to characterize the various in-medium partonic energy loss mechanisms and their dependence on the quark mass.
The excellent particle...
Quarkonia play a unique role in probing the properties of the quark-gluon plasma (QGP). The dissociation of quarkonia due to the color screening was proposed as a direct signature of the QGP formation. On top of that, different states of quarkonium are expected to dissociate at different temperatures depending on their binding energies. Therefore, measurement of the expected sequential...
Measurement of the jet substructure and the distribution of final state hadrons within a jet provide a detailed look into both the partonic shower and hadronisation process. These processes can be studied using the transverse momentum ($j_\mathrm{T}$) and longitudinal momentum fraction ($z$) of constituent particles. ALICE has recently measured the transverse momentum distributions of the jet...
Energetic partons lose energy in the quark-gluon plasma (QGP) and then fragment and hadronize into showers of particles called jets. Measurements of the internal structure of these jets can constrain how energetic partons interact with the QGP. Though species-independent jet substructure measurements have made much progress recently, a complete understanding of the identified particle...
The ALICE detector at the CERN LHC is particularly suited to study light (anti)nuclei produced in high-energy collisions between hadrons. The formation mechanism of (anti)nuclei in these collisions is still one fundamental open question that is being addressed both theoretically and experimentally. This mechanism is investigated by comparing experimental data with phenomenological models such...
The initial QGP geometry of the quark-gluon plasma (QGP) is manifested as azimuthal anisotropy in final state particles of a nuclear collision in the plane transverse to the beam direction. This study measures the Fourier coefficients $v_{2}$ and higher order harmonics of charged particle distribution in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with 2018 data collected by the...
Relativistic heavy-ion collisions generate extremely strong electromagnetic fields, providing an ideal environment to study the electromagnetic excitation of the vacuum. Furthermore, the electromagnetic fields are sensitive to the charge distributions of the colliding nuclei which can be used to study the nuclear structure. The Breit-Wheeler process, the lowest-order decay mode of the QED...
Quarkonium production in high-energy proton-proton (pp) collisions is an important tool for studying perturbative and non-perturbative aspects of quantum chromodynamics (QCD) calculations. Charmonia are bound states of charm and anti-charm quark pairs. Their production process can be factorized into two stages: the heavy quark production and the formation of the bound state. The former...
Hard partonic scatterings, occurring at the early stages of heavy-ion collisions, produce jets, which experience the full evolution of the quark-gluon plasma (QGP). As they traverse through the QGP, jets lose energy through collisional and radiative processes, collectively known as the jet quenching. In semi-central heavy-ion events, the QGP takes an approximately elliptical shape in the...
Measurements of long-range angular correlations are one of the important tools to evaluate the interplay between the initial- and final-state effects in small collision systems in view of understanding the evidence of collectivity.
The charged-particle multiplicity distribution as a function of pseudorapidity ($\eta$) is asymmetric in p--Pb collisions. Since the mean free path depends on...
Two-particle correlation analyses are often used to study the spatial and temporal extents of the particle-emitting source in high-energy nuclear collisions. Information on the final state interactions amongst the particles under study can also be extracted from the measurement. For example, from the p-$\Lambda$ and p-$\Xi^-$ correlation functions, one could study the hyperon-nucleon (Y-N)...
In non-central Heavy-Ion collisions, a large orbital angular momentum is produced. A part of the orbital angular momentum can polarize the quarks and anti-quarks, hence the vector mesons, inside the medium. Recently, STAR measured the global spin alignment of φ(1020) mesons in Au+Au collisions from the first phase of the RHIC Beam Energy Scan I (BES I) program [1].
The global spin...
Hard-scattered partons ejected from high-energy collisions undergo fragmentation and hadronization, resulting in collimated sprays of particles that are clustered into jets. The Energy-Energy correlator (EEC) is a jet substructure observable used to study the time evolution of the parton shower. This observable re-contextualizes jet substructure study by using the distribution of angular...
When a jet injects energy and momentum into a droplet of QGP, it generates a wake that, after the QGP hadronizes, results in the creation of soft and semi-hard particles correlated with the jet direction. This medium response phenomenon plays a crucial role in describing various jet observables, as demonstrated by many jet quenching studies. However, the computational complexity of current...
Quarkonia have been long considered as key features in heavy ion collision to study the properties of the quark-gluon plasma. One of the key signatures is the sequential yield suppression for different quarkonium states in nucleus-nucleus (A+A) collisions compared to p+p collisions following the ordering of their binding energies. Moreover, sequential yield modification has also been observed...
We study the critical point effects on particle number fluctuations both in the crossover ($T > T_{\rm c}$) and mixed phase ($T < T_{\rm c}$) regions by means of molecular dynamics simulations of a Lennard-Jones fluid, motivated by the ongoing search for the QCD critical point in heavy-ion collisions.
In the crossover region, we find large fluctuations associated with the critical point in...
Large-$N_c$ QCD implies a duality between confined baryons and deconfined quarks at high baryon densities; it is called Quarkyonic matter. We present a model of Quarkyonic matter that is explicitly dual between quarks and baryons. The duality means that the free energy of the matter is expressed in two ways: One is as a functional of the quark distribution function in the momentum space,...
Event classifiers based either on the charged-particle multiplicity or on event topologies, such as spherocity and Underlying Event, have been extensively used in proton-proton (pp) collisions by the ALICE Collaboration at the LHC. These event classifiers became very useful tools since the observation of fluid-like behavior in high multiplicity pp collisions, for example radial and anisotropic...
Studying quarkonium production allows us to probe the properties of strongly interacting matter, such as the quark-gluon plasma and the gluonic matter in heavy nuclei. While such a probe is widely used, a complete understanding of the quarkonium production mechanism is not yet achieved, even for $p$+$p$ collisions. Therefore, quarkonium studies in $p$+$p$ collisions are essential for advancing...
Recent measurements of the baryon-to-meson production yield ratios between charm baryons ($\Lambda_\mathrm{c}^{+}$, $\Sigma_\mathrm{c}^{0,++}$, $\Xi_\mathrm{c}^{0,+}$, $\Omega_\mathrm{c}^{0}$) and $\mathrm{D}$ mesons ($\mathrm{D}^0$) in small collision systems show a significant enhancement with respect to the measurements performed in $e^{+}e^{-}$ collisions. These results were compared with...
In nucleus-nucleus collisions at LHC energies, a deconfined state of matter, the quark-gluon plasma (QGP), is formed. Generally, proton-proton (pp) collisions are used as a reference to study their fundamental properties. However, at the highest energy reached in LHC Run 2, pp collisions at high multiplicity seemed to exhibit signatures of collective phenomena similar to those observed in...
Constraining the three-dimensional structure of the initial state and transport properties of the Quark-Gluon Plasma (QGP) at different temperatures ($T$) and baryon chemical potentials ($\mu_B$) is a critical objective of heavy-ion programs at RHIC and the LHC. This work presents comprehensive measurements on both topics for various event-shape and centrality selections of Au+Au collisions at...
Two particle femtoscopy provide a powerful tool for studying the space–time dynamics of the hot and dense matter (QGP) created in these collisions such as the size, shape, and lifetime as well as advancing our understanding of the behavior of matter at extreme conditions by measuring the relative momentum correlations between pairs of particles emitted in the same direction from the collision....
We perform a non-perturbative calculation of quarkonium dissociation rates in the quark-gluon plasma (QGP) within a thermodynamic T-matrix approach. The latter resums an infinite series of ladder diagrams for heavy-light interactions appropriate for a strongly coupled QGP which are implemented via half-off-shell amplitudes accounting for recoil corrections and interference effects (related to...
The study of the production of non-prompt ${\rm J/\psi}$ originating from the decay of beauty hadrons, besides allowing to isolate the prompt ${\rm J/\psi}$ cross section from the inclusive ${\rm J/\psi}$ cross section, can be used to estimate open beauty-hadron production. Heavy-flavour particle production in pp collisions as a function of charged-particle multiplicity could provide insight...
One of the most pressing questions in both hot and cold QCD communities is what the physics mechanism responsible for modified parton densities in heavy nuclei is. One promising channel to address this question is the photoproduction of vector mesons, which is considered a clean probe to the nuclear parton structures.
We present a measurement of $\pi^+\pi^-\pi^+\pi^-$ photonuclear...
Collective flow is observed in high-energy proton-proton and proton-nucleus collisions where particle multiplicities are small and a quark-gluon plasma description is hard to justify. Here, we address the origin of such observations from a new angle, by performing an experimental investigation of the emergence of hydrodynamics in two-dimensional ultra-cold Fermi gases with with controllable...
Ultraperipheral nucleus-nucleus collisions produce very large photon fluxes such that fundamental quantum-mechanical processes can be observed and studied in a novel way. In this presentation, an observation of the $\tau$ lepton photoproduction at LHC is reported, using ultraperipheral lead-lead collision data collected by CMS. This measurement paves the way for a precise determination of the...
On the gravitational wave emission in the magnetic field
of a heavy-ion collision
In the classic 1961 paper of Gertsenshtein [1] he demonstrated that an electromagnetic wave can be transformed into a gravitational wave when propagating through an external, transverse magnetic field. Later in 1973, Zel’dovich calculated the fraction of energy of the electromagnetic wave transformed into the...
The ePIC detector is being designed as a hermetic, general-purpose detector for the Electron-Ion Collider (EIC). One of the key performance drivers for the physics programme at the EIC are the particle identification (PID) system, which enable the separation of pions, kaons, and protons in high multiplicity events over a wide phase space, with significant pion/electron suppression. To address...
The simple picture of a hard scattering per $p+p$ collision has been challenged by several measurements performed at LHC and RHIC, revealing a more complex dynamics of multiple parton interactions (MPI) which are essential to fully understanding particle production in hadronic collisions. Hard probe measurements at different particle multiplicity regimes in $p+p$ collisions provide a clean...
Jet quenching parameter $\hat{q}$ is essential for characterizing the interaction strength between jet partons and nuclear matter. Based on the quark-meson (QM) model, we develop a new framework for calculating $\hat{q}$ at finite chemical potentials, in which $\hat{q}$ is related to the spectral function of the chiral order parameter. A perturbative calculation up to the one-loop order...
The $B^\pm$ meson is produced more frequently than any other meson containing beauty quarks in pp collisions at the LHC. Measuring its production cross-section is important for two reasons. Firstly, it allows for testing perturbative quantum chromodynamics calculations. Secondly, it provides an essential reference for measurements of its nuclear modification factor ($R_{\rm A \rm A}$) in...
Identified hadrons have proven to be useful in elucidating the final state effects of heavy ion collisions. This includes in particular the important role that hadronization plays on a variety of final state observables. System size is known to influence various observables, and the overlap in system size between different collision systems has helped establish the commonality between them,...
Central exclusive production (CEP) is a diffractive process in which the colliding particles remain intact. Three different processes are involved: photon-photon exchange, photon-pomeron exchange and double-pomeron exchange. Each process produces distinguishable states with specific sets of quantum numbers, making CEP measurements a unique tool for searching for exotic resonances. Furthermore,...
We study the contribution to the equation of state from mesonic correlations in the Polyakov-loop Nambu--Jona-Lasinio model within the Beth-Uhlenbeck approach, with a focus on the spacelike region of the spectral function. We show that the inclusion of such excitations leads to a significant increase of the pressure of the model near the pseudocritical temperature of the chiral phase...
With the newly upgraded sPHENIX detector capable of performing high precision jet substructure measurements, we present a comprehensive and systematic jet substructure study at the Relativistic Heavy Ion Collider. The study includes a variety of key jet substructure variables such as jet angularities with and without soft-drop or collinear-drop grooming, as well as recoil-free di-jet and...
Two-particle number and transverse momentum correlations are sensitive probes of particle production and transport in AA collisions. Their shape and strength are sensitive to the interplay of all production processes, and are further influenced by transport mechanisms, including longitudinal, radial, and anisotropic flow. However, the correlations are also sensitive to instrumental effects,...
We have probed the effect of the nonextensivity on the transport properties related to the charge and heat in hot QCD medium at finite magnetic field and chemical potential. The coefficients associated with the charge and heat transport, such as the electrical conductivity, Hall conductivity, thermal conductivity and Hall-type thermal conductivity are determined using the nonextensive Tsallis...
Charge balance functions (BFs) were introduced at the beginning of the RHIC era as a tool to investigate the evolution of particle production in heavy-ion collisions and identify the presence of delayed hadronization as an indicator of the formation of long lived isentropic expanding quark gluon plasma in high-energy nucleus-nucleus (A--A) collisions. It later emerged that BFs are rather...
The study of event-by-event fluctuations of the mean transverse momentum, $\langle p_{\rm{T} }\rangle$, could probe the nature of the phase transition and seek evidence for temperature fluctuations. In this talk, event-by-event $\langle p_{\rm{T} }\rangle$ and higher order fluctuations of charged particles produced in pp collisions at $\sqrt{s}=5.02$ TeV, Xe--Xe collisions at...
Two-particle transverse momentum correlator $G_{2}$ was measured based on data collected from Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76\;\text{TeV}$. The evolution of the longitudinal width of the $G_{2}$ correlator vs. collision centrality nominally provides information about the specific shear viscosity, $\eta/s$, of the medium formed in the collisions. The $G_{2}$ correlator was also...
The strangeness content of the final state in ultrarelativistic heavy ion collisions has been studied through measurements of kaons, Λ, Ξ and Ω baryons in pp, pA and AA collisions. $\Sigma$ baryons contain a single strange quark and form a triplet, with the charge (+, 0, -) depending on the light quark content. In a thermal model scenario, these states are abundant enough to carry a...
Measurements of high-multiplicity pp and pA collisions at LHC energies have revealed that these small collision systems exhibit some quark-gluon plasma-like features, such as collective behaviour and strangeness enhancement, formerly thought to be achievable only in nucleus-nucleus collisions. A proposed method to narrow down the origin of these phenomena is to study the effect of MultiParton...
Light-flavor hadrons constitute the bulk of the particles produced in high energy hadronic collisions at LHC. Recent studies show that in high multiplicity pp and p—Pb collisions at LHC energies, particle production exhibits features that mimic the behaviors observed in AA collisions (e.g., mass-dependent pT hardening and strangeness enhancement). These features are a typical sign of the...
The sequential clustering of particles into jets offers an algorithmic connection of hadrons to the partons of the radiation shower. Jet substructure allows us to access the radiation history of a jet thereby providing a useful avenue to probe QCD through different energy scales. The N-point Energy Correlator (ENC) is a recently proposed observable that highlights this feature of jets as a...
The production of light (anti)nuclei in high-energy hadronic collisions has been studied in depth with the ALICE experiment at the LHC. Despite this, the production mechanism of light (anti)nuclei is still not well understood and remains a highly-discussed topic in the scientific community. One of the phenomenological models typically used to describe the hadronization process is the...
The NA60+ experiment, proposed for data taking in the next years, aims to investigate the high baryochemical potential region of the QCD phase space diagram, exploiting the large intensity of CERN SPS beams.
NA60+ will have the possibility to access the high $\mu_{B}$ region of the QCD phase diagram, by studying rare probes via a beam-energy scan with PbPb and p-A collisions in the...
Correlation function of baryons has been used in heavy-ion collisions to study the space-time structure, the dynamical evolution of the particle-emitting source, and final state interactions.
In this poster, we will present correlation functions of protons in Au+Au collisions at $\sqrt{s_{NN}}$ = 3.2 GeV from the second phase of the beam energy scan (BES-II) at STAR. The Lednicky-Lyuboshitz...
The pseudorapidity density of charged particles with different values of minimum transverse momentum ($p_\mathrm{T}$) thresholds of 0.15, 0.5, 1, and 2 GeV/c is measured in pp collisions at $\sqrt{s} =$ 5.02 and 13 TeV with the ALICE Run 2 set-up. The study is carried out for inelastic collisions with at least one primary charged particle having a pseudorapidity ($\eta$) within ±0.8 and...
Quarkonia measurements in heavy-ion collisions are important for understanding both initial-state effects on heavy-quark production and final-state interactions between heavy quarks and the hot and dense nuclear matter created in high-energy heavy-ion collisions.
The sPHENIX experiment at RHIC will begin its commissioning and first Au+Au data-taking run in 2023, and plans to measure the...
We examine in detail the mass, lifetime and spin structure of quarkonium in a rotating vortical medium, where the quark spin is not necessarily aligned with the vortex.
After justifying this set-up in terms of spin hydrodynamics, and outlining the expected dependence of spin and vorticity, we examine the mass, lifetime and spin density matrix of quarkonium.
Our analysis implies a novel...
Quarkonium production in high-energy hadronic collisions is sensitive to both perturbative and non-perturbative aspects of quantum chromodynamics (QCD) calculations. Indeed, the production of the heavy-quark pair is described by perturbative QCD while the formation of the bound state is a non-perturbative process, treated in different ways by available theoretical models. Quarkonium...
In ultra-relativistic heavy-ion collisions, strong electromagnetic fields arising from the Lorentz-contracted, highly charged nuclei can be approximated as a large flux of high-energy quasi-real photons that can interact via the Breit-Wheeler process to produce $e^{+}e^{-}$ pairs. The collision energy dependence of the cross section and the transverse momentum distribution of dielectrons from...
The transport properties of the quark-gluon plasma, which is produced in heavy-ion collisions, provide crucial information about quantum chromodynamics (QCD). Bayesian analysis has been highly effective in constraining QCD matter properties [1, 2]. When combined with additional flow observables, LHC Pb-Pb data at 5.02 and 2.76 TeV have significantly reduced the uncertainties [2]. However, our...
Collisions of small systems show signatures suggestive of collective flow associated with QGP formation in heavy-ion collisions. Jet quenching is also a consequence of QGP formation, but no significant evidence of it in small systems has been found to date. Measuring or constraining the magnitude of jet quenching in small systems is essential to determine the limits of QGP formation. The ALICE...
A crucial component to the Electron Ion Collider (EIC) program is the collider luminosity, with a target absolute (relative) uncertainty of less than 1% (exceeding 10⁻⁴ in precision). The luminosity determination will be achieved employing two complementary approaches, one by direct detection of bremsstrahlung photons and another using a Pair Spectrometer (PS) which utilizes e+e- conversions...
The sPHENIX experiment is comprised of two layers of hadronic calorimeters (HCal). The outer HCal is the outermost layer located outside the solenoid coil, and the inner HCal is positioned between the solenoid magnet and the Electromagnetic Calorimeter. The sPHENIX program, aimed at achieving precise jet measurements and analyzing the microscopic properties of the strongly interacting...
The sPHENIX experiment has achieved a major milestone with the construction and installation of the cutting-edge three-layer Monolithic-Active-Pixel-Sensor (MAPS) based VerTeX detector (MVTX) in April 2023, in preparation for first beam in Spring 2023. The MVTX is the innermost tracking detector, boasting a spatial resolution of 5 $\mu$m and covering 2.5-4.0 cm radially, and a pseudorapidity...
We explain how spin alignment of vector mesons can be induced by background color fields. Our study is based on the quantum kinetic theory of spinning quarks and antiquarks and incorporates the relaxation of the dynamically generated spin polarization. The spin density matrix of vector mesons is obtained by quark coalescence via the Wigner function and kinetic equation. Our approach predicts a...
Transverse Λ polarization observed over four decades ago contradicted expec-
tations from early leading-order perturbative QCD calculations. Measurements
of Λ polarization from unpolarized pp and pA collisions have been previously
observed to increase as a function of xF and pT up to a few GeV range and
approximately independent of beam energy. Recent studies have linked polar-
ization to...
The validity of the Statistical Hadronization Model (SHM) has been successfully tested to adequately reproduce hadronic particle abundances over nine orders of magnitude in high energy collisions of heavy ions. Assuming a thermally equilibrated system, experimental particle yields at RHIC and the LHC serve as an anchor for the determination of common freeze-out parameters in the QCD phase...
Higher-order fluctuations of the net-proton number distributions in heavy-ion collisions are expected to be sensitive to a QCD critical point. These fluctuations can be obtained by measuring various order of cumulants, $C_n$, of the net-proton multiplicity distributions. The collision energy dependence of net-proton $C_4/C_2$ from Beam Energy Scan I hints at a possible enhancement from...
The ratio between (multi-)strange and non-strange hadron yields increases with the multiplicity of charged particles produced in hadronic collisions, revealing a smooth transition from low multiplicity pp collisions to central Pb-Pb collisions. The microscopic origin of this behaviour, known as strangeness enhancement, has yet to be understood. The data collected by the ALICE experiment during...
The production of strange quarks and antiquarks in high-energy collisions of
heavy ions is a significant indicator for the creation of a state of matter known
as Quark-Gluon Plasma (QGP). The QGP is characterized by the liberation of
quarks and gluons from their confinement inside hadrons. Due to their prompt
decay via weak interactions, strange quarks and antiquarks are not present...
Strangeness production is considered a sensitive probe to the properties of the medium created in heavy-ion collisions. The RHIC Beam Energy Scan Program (BES) is designed to investigate the QCD phase diagram and search for a potential QCD critical point. The BES-program covers a wide energy range from $\sqrt{s_{\rm{NN}}}$ = 3 to 54.4 GeV. Of particular interest is the high baryon density...
Neutron star equations of state that can sustain heavy neutron stars over 2 Msun necessitate a large, rapid rise in the speed of sound. The family of equations of states, which assume electric neutrality along beta equilibrium and vanishing temperatures, with large bumps in the speed of sound have been suggested to be incompatible with the equation of state extracted from heavy-ion...
$K_{1}$ and $K^{*}$ mesons are chiral partners whose vacuum widths are smaller than 100 MeV. This makes these mesons ideal to study possible effects of chiral symmetry restoration in heavy-ion collisions. In a recent theoretical study, the $K_{1}/K^{*}$ ratio in heavy-ion collisions is expected to be substantially larger than the statistical hadronisation model predictions. The study of the...
Studies of gluon fragmentation at LEP have shown hints that gluon-initiated jets produce more baryons than quark-initiated jets. Our current knowledge of fragmentation functions is almost exclusively based on fits to data from $e^+ e^-$ collisions and semi-inclusive deep inelastic scattering processes, both of which are mainly sensitive to quark fragmentation, leaving gluon fragmentation...
In nuclear collisions at low RHIC energies, although $s$ and $\bar{s}$ quarks are produced in pairs, there is a significant excess of $\Omega^{-}$ over ${\bar{\Omega}}^{+}$ which suggests that $\Omega^{-}$ carries a net baryon number. Such an excess of net baryon number at mid-rapidity in Au+Au collisions manifests effective mechanisms of baryon number transport over a large rapidity gap....
Short-lived resonances are ideal probes to study the properties of the hadron gas phase created in heavy-ion collisions in the post-hadronization phase. Since the resonance lifetime is comparable to that of the hadron gas phase, their yields are affected by the competing rescattering and regeneration effects. These can be studied experimentally by measuring the yield ratio of resonances to the...
Two-particle correlation functions give insight into the microscopic details of the production and transport mechanisms of conserved quantum numbers. In this contribution, new final measurements by the ALICE Collaboration of $\Xi-\pi$, $\Xi-$K, $\Xi-$p, $\Xi-\Lambda$, and $\Xi-\Xi$ correlation functions are presented to study how charge, strangeness, and baryon numbers are balanced in...
We present a new experimental method to study three-body nuclear systems by measuring correlations in the momentum space of deuteron-hadron pairs produced in proton-proton collisions at the LHC. The study of three- and many-body dynamics has been a long-standing goal in nuclear physics, particularly for understanding the structure of light nuclei and describing neutron-rich and dense nuclear...
Fluctuations of conserved charges, such as baryon number, electric charge, and strangeness, are a unique tool for studying the phase diagram of strongly interacting matter. The cumulants of the distributions of the conserved charges in heavy-ion collisions can be related to the equation of state in lattice QCD (LQCD), making first-principles calculations accessible in the experiment. Recent...
Angular correlations and polarization studies provide valuable insights into the vector meson production mechanism, including interference effects as well as information on the nuclear geometry of the target. In this talk, we present two new results. We will report the first measurement of the polarization of both coherent and incoherent J/psi photoproduction in ultra-peripheral Pb--Pb...
We present a new model for jet quenching via coherent gluon radiation and elastic scatterings off medium partons. 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 act as field dressing of...
The study of the suppression of the leading two hadrons within jets, by virtue of being robust against the underlying event background, provides an insight into the onset of quenching in the history of the evolution of relativistic heavy-ion collisions, which can help discriminate between different partonic energy loss mechanisms. The modification of their flavor correlations, on the other...
In studies of QGP, it has been observed that at high-energy heavy-ion (A$+$A) collisions, high-momentum particles with light and heavy flavors receive significant suppression. This indicates that particles lose their energies in QGP. One of the most important topics is to quantify the energy loss and to investigate the energy loss mechanism.
PHENIX measured the fractional momentum loss,...
We discuss the reconstruction of target jet and the framework of quantifying its internal substructure. Due to momentum and charge conservation, target and current correlation can be exploited which significantly constrains the event-wide particle distributions. We demonstrate this method using Pythia simulations of electron-proton collisions in the context of determining the flavor and...
In the exploration of the nuclear matter phase diagram, the susceptibilities of conserved charges are useful theoretical tools to probe the existence of a $1^\text{st}$ order phase transition, and a possible critical endpoint. They can be related to the cumulants of the considered net-charges, for which STAR collaboration recently published experimental measurements of proxies, in Au-Au...
In heavy ion collisions, the measured spectrum of direct photons at RHIC and the LHC has been found as azimuthally anisotropic as pions. In particular, a large elliptic flow of the direct photos has been observed, which strongly contradicts conventional theoretical predictions, leading to the well-known “direct photon puzzle”.
In this talk, instead of a strong magnetic field assumption...
Despite the success of hydrodynamic models in describing heavy-ion collisions, there have long been questions about its regime of validity. Recently-derived conditions on the causality of the hydrodynamic equations [1] can give a concrete answer --- if evolution is acausal, it is not a faithful representation of the underlying QCD theory. It is now known that current simulation models reach...
We employ the AdS/CFT correspondence to study the jet quenching effect in Quark-gluon plasma in heavy-ion collisions.The nuclear modification factor $R_{AA}$ and elliptic flow parameter $v_{2}$ are studied in different-centrality collisions at RHIC and LHC.Our numerical results agree with data.Magnetic field and chemical potential of the medium are also considered for the observable...
Understanding the modification of jets and high-p_T probes in small systems requires the integration of soft and hard physics. We present recent developments in extending the JETSCAPE framework to build an event generator, which includes correlations between soft and hard partons, to study jet observables in small systems. The multi-scale physics of the collision is separated into different...
The method of moments has been employed to derive relativistic fluid-dynamical theories from the Boltzmann equation for the past decades [1]. This approach consists in expanding the single-particle distribution function using a basis of irreducible momenta, where the expansion coefficients are the irreducible moments of the nonequilibrium distribution function [2]. Unlike the Chapman-Enskog...
The study of strongly interacting matter under external conditions (such as high temperatures and/or baryon densities) provides unique insights into its fundamental theory, Quantum Chromodynamics (QCD). A nonzero angular momentum imposed on a QCD system can bring rich and intriguing phenomena, with the proton spin structure being a perfect example. A much larger QCD system with substantial...
The shear viscosity (eta) of a quark-gluon plasma in equilibrium can be calculated numerically using the Green-Kubo relation or analytically using several methods, including the Israel-Stewart, Navier-Stokes, relaxation time approximation, and Chapman-Enskog methods. In this work [1], we first examine these analytical methods for isotropic as well as anisotropic two-body scatterings. We...
Experiments at the future Electron-Ion collider pose stringent requirements on the tracking system for the measurement of the scattered electron and charged particles produced in the collision, as well as the position of the collision point and any decay vertices of hadrons containing heavy quarks. Monolithic Active Pixel Sensors (MAPS) offer the possibility of high granularity in combination...
The sPHENIX detector is the next generation experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Starting commissioning in May, it will collect high statistics data sets from ultra relativistic Au+Au, p+p and p+Au collisions in the next 3 years. The readout is a combination of triggered readout for calorimeters and streaming readout for the silicon...
When studying the properties of the Quark-Gluon Plasma (QGP) formed in relativistic heavy ion collisions, it is necessary to classify the events based on the size and shape of the QGP. Typically, events are categorized by mapping the impact parameter, which cannot be measured directly, to a bulk observable that varies monotonically with it, such as soft particle production. In the mapping,...
Recent experimental results present collectivity also in small systems with high-multiplicity. Today these phenomena are not completely understood: it is an important question whether the presence of the QGP is necessary for the observed collectivity or not. Moreover, the connection between the experimental observables and theories is not trivial. In our phenomenological study we introduce the...
Universality is omnipresent when certain classes of microscopic theories are coarse-grained into effective macroscopic descriptions. Hydrodynamic theories are such macroscopic descriptions in long-wavelength, low-frequency limits of many quantum field theories. On the phenomenological side, hydrodynamics not only serves as a successful macroscopic description of the Quark-gluon plasma (QGP) in...
Dielectrons are an exceptional tool to study the evolution of the medium created in heavy-ion collisions. In central collisions, the energy densities are sufficient to create a quark-gluon plasma (QGP). Thermal e$^{+}$e$^{-}$ pairs with invariant masses around 1.5 GeV/$c^{2}$ can be used to estimate the early average temperature of the QGP.
At LHC energies, the cross section of...
The question of identifying the baryon topological structure encoded in the baryon junctions has a long history and was recently addressed in the measurements of baryon stopping by the STAR collaboration. We suggest considering this question in a simple, exactly solvable model that allows us to clearly separate the topological junction structure from the valence quarks. We find that baryon...
The sPHENIX detector at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) has a broad experimental QCD physics program focused on jets, their substructure, and open and closed heavy flavor production. To measure these observables, the sPHENIX tracking system is composed of a silicon vertex and strip detector, continuous-readout time projection chamber, and...
The tracking reconstruction procedure for the sPHENIX experiment combines data from its silicon pixel detector, silicon strip detector, time projection chamber, and micromegas-based outer tracker modules to produce tracks that trace a given particle's path through 57 total sensor layers. After clustering of the raw data is completed, the track seeding modules identify chains of clusters that...
We discuss the transport coefficients of heavy quarkonia moving in high temperature QCD plasmas. The thermal width and mass shift for quarkonia are closely related to the momentum diffusion coefficient and its dispersive counterpart for heavy quarks, respectively. For quarkonium at rest in plasmas, the longitudinal gluon part of the color-singlet self-energy diagram is sufficient to determine the...
We present a new study of two-particle correlations as extracted with the CMS experiment in 8.16 TeV proton-lead (pPb) events with large rapidity gaps in the proton going region. Recent comparisons of the cross sections of such events measured in CMS as a function of the rapidity gaps (i.e., regions devoid of any particle activity) with several generators suggest that such events have...
We investigate how the event-by-event fluctuations of the final-state distribution function of nucleons physically affect the yield ratio of light nuclei based on the coalescence model.
The yield ratio of light nuclei, $N_tN_p/N_d^2$ (with $N_t$, $N_p$, and $N_d$ being triton, proton, and deuteron numbers, respectively) [1,2], is one of the observables suggested for a possible signal of the...
The Ridge behavior in high-multiplicity proton-proton collisions has been discussed a lot since it was first reported. However, small systems like proton-proton collisions are not enough to generate a medium called Quark-Gluon Plasma (QGP) in which the Ridge behavior is explained with high-order flows. In this work, we suggest the pure kinematic mechanism between jets and medium partons as...
Experimental data on a wide range of jet observables measured in heavy ion collisions provide a rich picture of the modification of jets as perturbative probes and of the properties of the quark-gluon plasma. However, their interpretation is often limited by the assumptions of specific quenching models, and it remains a challenge to establish model-independent statements about the universality...
Rare probes such as jets and heavy flavor hadrons provide unique opportunities to study the short-distance scale properties of the QGP created in heavy ion collisions. For example, recent measurements at the LHC and RHIC indicate that jet energy loss is correlated with the distance traveled through the QGP medium, and as a result, the initial geometry of the QGP. While estimates of...
The ALICE Collaboration presents a new experimental approach to explore the interactions in three-hadron systems by analyzing femtoscopic correlation functions of deuteron-hadron pairs produced in high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV and in Pb--Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ $\mathrm{TeV}$ at the LHC. The measured p-d correlation function can only be explained if...
Measuring the jet substructure in heavy-ion collisions provides exciting new opportunities to study detailed aspects of the dynamics of jet quenching in the hot and dense QCD medium created in these collisions. In this talk, we present new comprehensive ATLAS measurements of jet suppression and substructure performed using various jet radii and grooming techniques. New measurements of...
In vacuum, the spacetime location where a gluon splits into a quark-antiquark pair is not a well defined observable. In heavy-ion collisions, the `formation time’ of a splitting takes on meaning due to interactions with the medium and is a critical feature for the phenomenology of medium-modified parton showers. The $g\rightarrow c\bar{c}$ splitting is especially suited to study this formation...
Gluons are found to become increasingly dominant constituents of nuclear matter when being probed at higher energies or smaller Bjorken-$x$ values. This has led to the question of the ultimate fate of nuclear gluonic structure at extreme density. In ultraperipheral collisions (UPCs) of relativistic heavy ions, the coherent heavy-flavor vector meson production via photon-nuclear interactions is...
Many new jet substructure observables have been studied in recent years, with particular attention to those which can be calculated by perturbative QCD. N-point energy correlators are currently attracting both theoretical and experimental interest. To comprehensively study the perturbative and non-perturbative aspects of jet structure, we measured the energy-energy correlators (EEC) that...
Partons traversing the hot and dense medium of deconfined color charges produced in collisions of heavy nuclei are expected to lose their energy primarily through medium-induced gluon bremsstrahlung. As a result, the amount of induced energy loss is expected to depend on the QCD color charge carried by the parton, i.e. depend on whether it is a quark- or a gluon-initiated jet. In this talk,...
ALICE has been the first experimental collaboration observing a moderate nuclear suppression down to low Bjorken x in lead nuclei using coherent J/$\psi$ photoproduction. In this talk, we present new results extending the studies of the photonuclear cross section by covering the Bjorken-x interval of $1.1 \cdot 10^{-5} < x < 3.3 \cdot 10^{-2}$, corresponding to the photon-nuclear energies $17...
Since the discovery of the jet quenching at RHIC, the in-medium interaction of hard scattered partons with the nuclear medium created by high-energy heavy-ion collisions has been an excellent tool to understand not only the transport properties of the medium but also its time evolution towards hadronization. The multi-differential measurement of the high momentum two-particle correlations can...
Authors: G. Coci, S. Glässel, V. Kireyeu, J. Aichelin, C. Blume, V. Kolesnikov, V. Voronyuk and E. Bratkovskaya
The formation of weakly bound clusters and hypernuclei in the hot and dense environment at midrapidity is one of the surprising phenomena observed experimentally in heavy-ion collisions from low SIS to ultra-relativistic LHC energies. This is also known as the `ice in a fire'...
We present a unique signal of jet-induced medium excitations: the enhancement of baryon-to-meson ratios around the quenched jets [1]. To illustrate this, we study jet-particle correlations and the distributions of jet-induced identified particles with respect to the jet direction in Pb+Pb collisions at the LHC via a multi-phase transport model. We find a strong enhancement of baryon-to-meson...
Ultraperipheral collisions of relativistic heavy ion beams lead to a diverse set of photon-nucleus (photonuclear) interactions. The measurements of particle production in photonuclear reactions can shed light on the QCD dynamics of the novel, extremely asymmetric colliding systems, with energies between those available at RHIC and the LHC. Previous studies by ATLAS indicate significant...
We present a novel multi-fluid approach to simulate heavy-ion collisions in the region of RHIC Beam Energy Scan and FAIR experiments. This region of collision energies from few to few tens of GeV is particularly interesting for the exploration of dense baryon matter and search of the critical point of QCD. However, fluid-dynamical modelling here poses notable challenges. Contraction of the...
Recent experimental results on the Λ+c/D0 ratio in proton-proton collisions – strongly enhanced compared to expectations relying on universal fragmentation fractions/functions in different colliding system, from e+e− to pp – led to speculations about possible medium effects affecting hadronization, previously considered a distinctive feature only of heavy-ion collisions. Here we show how the...
The recent measurements of NA61/SHINE at the CERN SPS revealed a large violation of isospin symmetry. The ratio of charged to neutral kaons was measured to be 1.22 ± 0.06 in Ar+Sc collisions at 75A GeV/c. This contribution will present the experimental details of this intriguing result. It will also compare it to the world data on charged to neutral kaons ratio in nucleus-nucleus collisions....
We perform a systematic study on the local and global spin polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons in relativistic heavy-ion collisions at beam energy scan energies via the (3+1)-dimensional CLVisc hydrodynamics model with AMPT and SMASH initial conditions. Following the quantum kinetic theory, we decompose the polarization vector as the parts induced by thermal vorticity,...
Measurements of quarkonia production in peripheral and ultra-peripheral
heavy-ion collisions are sensitive to photon-photon and photon-nucleus interac-
tions, the partonic structure of nuclei, and to the mechanisms of vector-meson
production. LHCb has studied production of the J/ψ and ψ(2S) charmonium
states in peripheral and ultra-peripheral collisions using PbPb data at...
The measurement of jets recoiling from a trigger hadron (hadron+jet) provides unique probes of medium-induced modification of jet production. Jet deflection via multiple soft scatterings with the medium constituents may broaden the azimuthal correlation between the trigger hadron and the recoiling jet. In addition, the tail of this azimuthal correlation may be sensitive to single-hard Moli`ere...
Characterization of the quark--gluon plasma (QGP) created in ultrarelativistic heavy-ion collisions requires identifying observables sensitive to the different phases of the collision. Previous studies have shown that measurements of the azimuthal anisotropic flow and the complex interplay between its harmonics can provide valuable information on the QGP transport properties.
In this talk,...
We present a novel approach to jet substructure in heavy-ion collisions formulated in terms of correlation functions of flux operators (energy correlators). This approach is based on the insight that the time scales in the jet’s evolution are imprinted into the angular scales of the correlator spectra. We study the two-point correlator of an in-medium massless quark jet, showing its...
Functional forms of the neutron star Equation of State (EoS) are required to extract the viable EoS band from neutron star observations. Realistic nuclear EoSs, containing deconfined quarks or hyperons, present nontrivial features in the speed of sound such as bumps, kinks, and plateaus. Using modified Gaussian processes to model EoSs with nontrivial features, we show in a fully Bayesian...
The intriguing phenomena emerging in the high-density quantum chromodynamics (QCD) matter are being widely studied in the heavy ion program at the LHC and will be understood more deeply during the high-luminosity LHC (HL-LHC) era. The CMS experiment is under the Phase II upgrade towards the HL-LHC era. A new timing detector is proposed with its timing resolution for minimum ionization...
One of the main goals in the study of hadronic interactions at LHC energies is the attempt to characterize the mechanisms involved in particle production in different regimes. The charged-particle multiplicity is one of the most interesting observables in these kind of studies. On the one hand, the pseudorapidity dependence of charged-particle production provides information on the partonic...
We study the equilibration of a high-momentum parton traveling through a Quark-Gluon Plasma using QCD kinetic theory. We show that the energy and particle number are first transported to the soft sector by collinear cascade and then isotropized by elastic scatterings. For a static thermal background, we find that the jet wake can be described by a thermal distribution function with...
The study of jet production in small collision systems is essential for testing our understanding of perturbative and non perturbative QCD and cold nuclear matter effects. In addition, studies at high multiplicity in small collision systems exhibit signatures of collectivity, which is still not fully understood within a unified picture across system size. Jet quenching in small systems is not...
The ALICE experiment is preparing for the ITS3 upgrade, which is set to take place during the LHC Long Shutdown 3. The aim of this upgrade is to replace the three innermost tracking layers with truly cylindrical wafer-scale Monolithic Active Pixel Sensors (MAPS). By adopting this innovative technology, ALICE will further reduce the material budget and the distance from the interaction point,...
Even though the quark-gluon plasma produced in high-energy heavy ion collisions has been studied in detail for years, there are still properties that are not known to a good precision. One example of such property is the medium resolution length, which is related to the smallest angle of emission where the medium can still resolve the daughter particles as individual particles. This can be...
The FoCal is a high-granularity forward calorimeter to be installed as an ALICE upgrade subsystem during the LHC Long Shutdown 3 and take data during the LHC Run 4.
It will cover a pseudorapidity interval of $3.4 < \eta < 5.8$, allowing to explore QCD at unprecedented low Bjorken-$x$ of down to $\approx 10^{-6}$ -- a regime where non-linear QCD dynamics are expected to be sizable.
It...
Jets provide a powerful tool to study the properties of hot nuclear matter and its effect on quantum processes. The degree of modification of jets by the medium depends on how well the medium can resolve the internal jet structure. In this work, we investigate the interplay between the multi-partonic structure of jets and their interaction with a strongly-interacting medium. Specifically, we...
Luminosity is an essential quantity to measure the cross section of any process. At the Electron Ion Collider (EIC), it will be measured using the Bethe-Heitler process in which a real photon is radiated in the electron-ion (p or A) scattering: e + p(A) → e + p(A) + Ɣ. The cross section is very large with respect to DIS and can be precisely calculated in leading-order QED, as was done by...
It has been postulated that nonperturbative quantum chromodynamics (QCD) evolution of a single parton in the vacuum can develop long-range collective effects of a multiparton system, reminiscent of those observed in high-energy nuclear interactions from the formation of a quark-gluon plasma. A search for such QCD collective effects is performed by the CMS experiment via correlation...
We derive the equations of motion of relativistic magnetohydrodynamics from the Boltzmann equation using the method of moments. We generalize the references [1, 2] and consider a fluid to be a locally neutral system composed of a particle with opposite charges, with vanishing dipole moment or spin, so that the fluid has vanishing magnetization and polarization.
We demonstrate that the...
The proposed Electron-Ion Collider (EIC) will utilize high-luminosity high-energy electron+proton ($e+p$) and electron+nucleus ($e+A$) collisions to solve several fundamental questions including searching for gluon saturation and studying the proton/nuclear structure. Due to their high masses ($M_{c,b} > \Lambda_{QCD}$), heavy quarks do not transfer into other quarks or gluons once they are...
The observation of signs of collectivity in small systems has highlighted the need
for a better understanding of equilibration in small and large collisions systems.
In search of this, the QCD effective kinetic theory formulated by Arnold, Moore
and Yaffe (AMY) [1] has emerged as a promising candidate. In order to fully exploit
the theory also for phenomenology we introduce ALPACA [2], a...
Antinuclei can be produced in space either by collisions of high-energy cosmic rays with the interstellar medium or from the annihilation of dark matter particles stemming into standard model particles. High-energy hadronic collisions at accelerators create a suitable environment for producing light (anti)nuclei. Hence, studying the production of antinuclei in pp collisions at the LHC can...
We propose a novel approach to investigate the evolution of jets in heavy-ion collisions by employing a combination of jet substructure measurements. Our method focuses on isolating the perturbative regime of jet evolution. As a proof of concept, we analyze the distribution of the hardest splitting above a transverse momentum scale, $k_{t,cut}$, in high-$p_t$ jets. For a $k_{t, cut}$ that is...
NA60+ is a new proposed experiment designed to study the phase diagram of the strongly interacting matter at high baryochemical potential from 200 to 550 MeV at the CERN SPS. It is focused on precision studies of thermal dimuons, heavy quark and strangeness production in Pb--Pb collisions at center of mass energies ranging from 6 to 17 GeV.
The proposed experimental apparatus is composed of...
In heavy nuclei the neutron distribution has a larger spatial extent than the proton distribution. This size difference represents the so-called neutron skin and is determined by the strong nuclear force in the same regime as that determining the masses and radii of neutron stars. The neutron skin of $^{208}$Pb, owing to its simple structure and large neutron excess, has been the target of...
In relativistic heavy-ion collisions, the longitudinal fluctuations of the fireball density caused, e.g., by baryon stopping fluctuations result in event-by-event modifications of the proton rapidity density distribution. I will present the multiparticle rapidity correlation functions due to the varying distribution width of the proton rapidity density in central Au+Au collisions at low...
In this talk I discuss 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. I explain the qualitative properties and systematics of the second-order susceptibility of the net-baryon number density for individual positive- and...
We use QCD kinetic theory to compute photon and dilepton production in the chemically equilibrating out-of-equilibrium Quark-Gluon Plasma created in the early stages of high-energy heavy-ion collisions. We compare the non-equilibrium rates to the production in a thermal QGP and extract the dependence of pre-equilibrium photon and dilepton production on the kinetic and chemical equilibration...
Baryon number is a strictly conserved quantity in QCD and is conventionally assumed to be divided equally among the three valence quarks in baryonic matter. An alternative model is the baryon junction: a Y-shaped configuration of nonperturbative gluons that is connected to all three valence quarks and carries the baryon number. Neither of these theories has been experimentally verified. ...
Using a relativistic transport model to describe the evolution of the quantum chromodynamic matter produced in Au+Au collisions at $\sqrt{s_{NN}}=3-200$ GeV, we study the effect of a first-order phase transition in the equation of state of this matter on the yield ratio $N_tN_p/ N_d^2$ ($tp/d^2$) of produced proton ($p$), deuteron ($d$), and triton ($t$). We find that the large density...
We present a study of flow and hyperon polarization observables at RHIC BES energies in a MUlti Fluid simulation for Fast IoN collisions (MUFFIN) model. MUFFIN is based on a multi-fluid approach to relativistic heavy-ion collisions, and treats the initial stage of heavy-ion reaction as mutual inter-penetration of baryon-rich fluids. It is implemented from scratch with the use of a versatile...
At LHC energies it is possible to generate BSQ (baryon, strangeness, and electric) charge density fluctuations from gluon splittings into quark anti-quark pairs, generated within the ICCING model. This creates an opportunity to implement and quantify the BSQ charge dynamics in the very well controlled regime of heavy ion collisions simulations. In this work, we implement BSQ charge dynamics in...
In relativistic heavy ion collisions, the charged ions produce an intense flux of equivalent photons. Thus, photon-induced processes are the dominant interaction mechanism when the colliding nuclei have a transverse separation larger than the nuclear diameter. In these ultra-peripheral collisions (UPCs), the photon provides a clean, energetic probe of the partonic structure of the nucleus,...
Our ability to predict thermodynamic observables and determine the QCD critical point at real values of chemical potentials is severely limited by the infamous sign problem. To address this issue, there are two common approaches: expanding the QCD partition function in a Taylor series with respect to the charge chemical potentials ($\mu_{B,Q,S}$) or analytically continuing from imaginary...
Thermal photon emission from the QGP is visible in the $p_T$ spectrum of direct photons measured in heavy-ion collisions, producing a characteristic exponential dependence of the spectrum at low $p_T$. The ALICE, PHENIX and STAR Collaboration have quantified this inverse slope $T_{eff}$, measuring $\approx 200$-$400$ MeV, close to the range of QGP temperatures seen in hydrodynamic simulations...
We first assemble a full set of the Boltzmann Equation in Diffusion Approximation (BEDA) for studying thermalization/hydrodynamization and quark production in out of equilibrium systems. In the BEDA, the time evolution of a generic system is characterized by four space-time dependent quantities: the jet quenching parameter $\hat q$, the effective temperature $T_*$ and two others that...
A hot and dense matter exhibiting collective flow behavior with almost no viscous dissipation has been discovered in ultrarelativistic nuclear collisions. To constrain the fundamental degrees of freedom and equation of state of this matter, this talk will present an extraction of its speed of sound using head-on lead-lead collision data collected by the CMS experiment at a center-of-mass...
Determining the structure of protons and nuclei at high energy is one of central goals of the heavy-ion collisions and the future Electron-Ion Collider (EIC). We first use Bayesian inference within the color glass condensate framework to extract the proton shape fluctuations from HERA exclusive vector meson production data at $x = 10^{-3}$. With this input, we employ the JIMWLK evolution for...
The STAR Collaboration has reported results from a blind analysis of isobar collisions (${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$, ${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$) at $\sqrt{s_{\mathrm{NN}}}=200$ GeV on the search for the chiral magnetic effect (CME). Significant differences were observed in the measured multiplicity ($N$) and elliptic anisotropy ($v_{2}$) between the two...
We use QCD effective kinetic theory to calculate far-from-equilibrium dynamics in the presence of quarks on an event-by-event basis within the KoMPoST framework. We present non-equilibrium response functions and dynamical evolution pertinent to the early time dynamics of heavy-ion collisions at the highest energies. The KoMPoST framework with conserved baryon, strangeness, and electric charges...
The interaction of heavy quarks with the quark-gluon plasma (QGP) affects their azimuthal distribution and transverse momentum ($p_\mathrm{T}$) spectrum, hence azimuthal anisotropy coefficients ($v_{n}$) and nuclear modification factors ($R_\mathrm{AA}$) of heavy flavor hadrons are important probes of the QGP. However, a simultaneous modeling of $v_{n}$ and $R_\mathrm{AA}$ is still...
Over the past decades, the properties of dense matter have been widely concerned in connection with hypernuclei and hyperons. Their existence inside neutron stars softens the Equation of State (EoS), consequently limiting their masses to be lower than two solar masses (known as the "hyperon puzzle"). The limited number of experimental references in the region of high baryon chemical potential...
We explore the far-off-equilibrium aspects of the (1+1)-dimensional early-stage evolution of a weakly-coupled quark-gluon plasma using hydrodynamics and kinetic theory. For a large set of far-off-equilibrium initial conditions we observe that the macroscopic evolution appears to violate simple rules based on the second law of thermodynamics. We provide an in-depth microscopic understanding of...
The thermal fluctuations in the QGP medium formed in heavy ion collisions present themselves as event-wise $[p_\mathrm{T}]$ fluctuations in the final state. Recent studies have shown that in ultra-central collisions, fluctuations are sensitive to radial flow, random thermal motion, and nuclear deformation. They can provide constraints on the extent of thermalization of the QGP droplet. Also of...
Constraining the initial strong electromagnetic field effects, three-dimensional structure of the initial state, and the transport properties of the Quark-Gluon Plasma (QGP) at different temperatures ($T$), and baryon chemical potentials ($\mu_B$) are critical objectives of the heavy-ion program at RHIC. The dominance of Faraday+Coulomb effect during the initial stages of non-central heavy ion...
One of the most unexpected findings of the LHC heavy ion program is the observation of stronger suppressions of the excited quarkonium states compared to the ground states in proton-lead (pPb) collisions. Such differences imply dissociation effects occurring at late stages, after the evolution of heavy quark pairs into well-defined physical states. The variety of binding energies within the...
Among the most iconic results of Run 1 and Run 2 of the LHC is the observation of enhanced production of (multi-)strange to non-strange particles, gradually rising from low-multiplicity to high-multiplicity pp or p-Pb collisions and reaching values close to those measured in peripheral Pb-Pb collisions. More insightful information about the production mechanism could be provided by measuring...
A central question in heavy-ion collisions is how the initial far-from-equilibrium medium evolves and thermalizes. In this work we use the two-particle irreducible (2PI) effective action for the first time to answer this question. This requires including the fast longitudinal expansion that characterizes heavy-ion collisions. Our framework, the 2PI effective action, is non-perturbative and...
With the tremendous accomplishments of RHIC and the LHC experiments and the advent of the future electron-ion collider on the horizon, the quest for compelling evidence of the color glass condensate (CGC) has become one of the most aspiring goals in the high energy quantum chromodynamics research. Pursuing this question requires developing the precision test of the CGC formalism. By...
A key open question in the study of multi-particle production in high-energy $pp$ collisions is the relationship between the "ridge" - observed azimuthal correlations between particles in the underlying event that extend over all rapidities and hard or semi-hard scattering processes. In particular, it is not known whether jets or their soft fragments are correlated with particles in the...
Proton-lead collisions at LHC energies offer a unique possibility to investigate initial state effects in nuclear collisions. Thanks to its wide acceptance, ATLAS can measure several probes that can help characterize these effects over a wide kinematic range. By analyzing the centrality dependence of dijet production, it is possible to investigate the suppression of dijet events in central...
Suppression of open heavy flavors and quarkonia in heavy-ion collisions is among the most informative probes of the quark-gluon plasma (QGP). Interpreting the full wealth of data obtained from the collision events requires a precise understanding of the evolution of heavy quarks and quarkonia as they propagate through the nearly thermal and strongly coupled plasma. Only in the past few years,...
We study consistently the effects of magnetic field on hot and dense matter. In particular, we look for differences that arise due to assumptions that reproduce the conditions produced in particle collisions or astrophysical scenarios, such as in the core of fully evolved neutron stars. We assume the magnetic field to be either constant or follow a profile extracted from general relativity...
A double copy between 2 > N QCD amplitudes and Gravity amplitudes at high energies was first discovered by Lipatov in 1981. In published work with G. Dvali[1], we showed how a double copy between Black Holes and the CGC arises, with both systems saturating the Bekenstein bound. We discuss how this dual picture points to some missing features of the CGC. Most importantly theoretical techniques...
We train a deep convolutional neural network to predict hydrodynamic results for flow coefficients, average $p_T$ and charged particle multiplicities in ultrarelativistic heavy-ion collisions from the initial energy density profiles event-by-event [1]. We show that the network can be trained accurately enough so that it can reliably predict the hydrodynamic results for the flow coefficients...
We present measurements of two-particle angular correlations of charged particles emitted in high-energy $e^+e^-$ collisions using data collected by the ALEPH detector at LEP between 1992 and 2000. The correlation functions are measured over a wide range of pseudorapidity and azimuthal angle as a function of charged particle multiplicity. Previous measurement with LEP1 data at $\sqrt{s}=91$...
Hypernuclei are bound states of nuclei with one or more hyperons. Precise measurements of hypernuclei properties and their production yields in heavy-ion collisions are crucial for the understanding of their production mechanisms. The strangeness population factor, $S_{\rm A}=(^{A}_{\Lambda}\mathrm{H}/^{A}\mathrm{He})/(\Lambda/p)$ (A=3,4), is directly related to the ratio of light nuclei and...
Measurements of dijets that traverse a quark-gluon plasma can provide insights into the jet energy loss in heavy ion collisions. Furthermore, considering jets of various sizes can help elucidate how the parton energy is transferred to the medium as well as the medium response. Measurements of the dijet momentum imbalance and nuclear modification factors for leading and subleading jet pairs...
Nowadays, relativistic dissipative hydrodynamics including effects of finite viscosities is commonly used to extract transport properties of the quark gluon plasma (QGP), such as shear viscosity and bulk viscosity, from experimental data. However, according to the fluctuation-dissipation relation (FDR) in non-equilibrium statistical physics, fluctuations and dissipation are always accompanied...
Investigating particle production in small systems has become instrumental
in probing non-perturbative contributions to hadron structure and hadroniza-
tion mechanisms. The LHCb spectrometer unique geometry at the LHC along
with its particle identification and tracking capabilities allow for new studies
of the multiplicity-dependent enhancement of strange hadrons in the forward
region....
Understanding the strong interaction between nucleons and hyperons is fundamental for the microscopic description of bound systems as well as for modeling the equation of the state of dense stellar objects, such as neutron stars. Conventional scattering and hypernuclei measurements are insufficient to support theoretical predictions about the interaction between hadrons containing strangeness....
The sPHENIX project is a new detector experiment at the Relativistic Heavy Ion Collider at BNL. Its aim is to study strongly interacting Quark-Gluon Plasma and cold-QCD by measuring photons, jets, jet correlations, and Upsilon family with high precision. To achieve these goals, a precise tracking system is necessary. The tracking system of the sPHENIX detector consists of the MVTX, TPC, TPOT,...
