Description
If you click the "Contribution list" below, you should find your poster listed below.
The Color Glass Condensate (CGC) effective theory predicts the earliest stage of relativistic heavy-ion collisions to be a classical state characterized by strong color fields called Glasma. The dynamics of the Glasma are fully determined by the classical Yang-Mills (YM) equations, for which no analytic solution exists. In this talk, we demonstrate how we linearize the YM equations within the...
Recent years have brought interest in the baryon dense region of the QCD phase diagram, probed by low energy heavy ion collisions (HICs) performed by the STAR Beam Energy Scan at RHIC, and by the HADES/CBM experiments at the upcoming FAIR facility. Such HICs are correctly described by hybrid simulations of hadronic transport and viscous hydrodynamics, connected initially by the fluidization of...
Studying the gluon density in nucleons and nuclei require measurements at low-x. The Forward Calorimeter (FoCal) upgrade for ALICE will provide just such measurements. FoCal comprises two components, an Electromagnetic calorimeter (FoCal-E) and a Hadronic Calorimeter (FoCal-H). This poster will present results from the first prototype that informed the design of the second prototype.
In...
We study the diffusion of heavy quarks in the early stages of high energy nuclear collisions. The background gluon fields are modeled by the standard MV initialization of the glasma, which is then evolved by means of the classical Yang-Mills equations. Heavy quarks are coupled to the evolving glasma fields via relativistic kinetic theory. We compute the momentum broadening as well as the...
Ultrarelativistic heavy-ion collisions create a hot and dense quark-gluon plasma (QGP) medium. In this talk, we discuss how the theory-dependent dynamics during the equilibration period affects late-time observables such as energy per rapidity and elliptic flow [1,2]. In particular, we point out discrepancies between the predictions of kinetic theory and relativistic hydrodynamics and discuss...
The centrality dependence of two-pion Bose-Einstein correlation functions is measured by the PHENIX experiment in $\sqrt{s_{NN}} = 200$ GeV Au+Au collisions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The data are well represented by Lévy-stable source distribution. We extracted the correlation strength parameter $\lambda$, the Lévy index of stability $\alpha$ and...
The measurement of fine splitting of observables between ${}^{96}$Ru-${}^{96}$Ru and ${}^{96}$Zr-${}^{96}$Zr collisions at RHIC has opened a new window in probing the deformation of these two isobar isotopes using high-energy nuclear physics. Since these two systems have the same mass, distributed in almost the same size spatial region, the nature of the collective evolution of both systems...
The gluon density has been observed to increase rapidly with energy, which would eventually violate unitarity. At high energies, however, nonlinear effects start to become important, slowing down the evolution of the gluon density and hence giving rise to gluon saturation. To study this saturation region of QCD one possibility is to look at diffractive processes, as being approximately...
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...
Centrality dependence of nuclear modification factor of Pi0 in d+Au collision shows a suppression in most central events, which is expected if QGP droplets are formed in small systems, but also a strange enhancement in peripheral collisions. To disentangle possible biases in centrality determination from energy loss , PHENIX presents invariant yields of high pT Pi0 and direct photons as a...
we investigate the existence of far-from equilibrium attractors in momentum moments of the one particle distribution function by means a 3+1D Boltzmann transport approach at fixed η/s with the full collision integral. Attractors are found in the normalized moments of the distribution function and in the evolution of the distribution function itself. We show the results in systems with Bjorken...
In the early stages of heavy-ion collisions, at the highest energies, the system begins in a highly anisotropic state which is far from equilibrium. At later times, the dynamic evolution of the system is well described in the framework of relativistic hydrodynamics which requires local thermodynamic equilibrium. The K\o{}MP\o{}ST framework has had some success in bridging the gap between these...
The collisions of $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr performed at RHIC in 2018, albeit originally intended for the search of the chiral magnetic effect, showed that high-energy heavy-ion collisions could be used as a high-precision tool to probe nuclear structure. One typically models such collision as an initial energy deposition in the vacuum, whose distribution...
In this work, the origin of anisotropic flow in hybrid approaches, combining viscous relativistic hydrodynamics as well as hadronic transport, is studied.
Anisotropic flow emerges in all stages, albeit being influenced by the shear viscosity in the hydrodynamic phase. Due to the theoretical uncertainties, hybrid approaches use several initial condition models, including SMASH IC, TRENTo and...
The transverse momentum transfer can be measured in exclusive processes. As this momentum transfer is Fourier conjugate to the impact parameter, exclusive processes in Ultra Peripheral Collisions (UPC) at the LHC and at the future EIC will provide access to the spatial distribution of nuclear matter in light and heavy nuclei at high energies.
In this talk we show how non-linear saturation...
The photoproduction of $J/\psi$ mesons in ultra-peripheral collisions of heavy ions is a well-known process to study nuclear dynamics at hadron colliders. In particular, the dependence of incoherent $J/\psi$ photoproduction on the Mandelstam variable $|t|$ enables to assess the significance of fluctuations of the spatial distribution, in the impact parameter plane, of the gluon fields within...
We compute the heavy quark momentum diffusion coefficient $\kappa$ using effective kinetic theory at initial stages during the bottom-up isotropization process. We find that the nonequilibrium diffusion coefficient can be approximated with the thermal diffusion coefficient to reasonable accuracy when matching the two for the same energy density. When matching for other quantities (screening...
In this talk, we report on the recent calculation of the total NLO dipole picture DIS cross sections for longitudinal and transverse virtual photons with quark masses [1,2,3]. This calculation has required solving a longstanding issue concerning quark mass renormalization in light cone perturbation theory. The quark masses are renormalized in the pole mass scheme, satisfying constraints from...
In the dipole picture of Deep Inelastic Scattering (DIS) at high energy, the virtual photon fluctuates into a quark-antiquark dipole that interacts with the target color field. This interaction at small-x is naturally described within the Color Glass Condensate (CGC) framework, and one can derive a perturbative Balitsky - Kovchegov (BK) evolution equation that describes the dependence of the...
The striking resemblance of high-multiplicity proton-proton (pp) collisions at the LHC to heavy ion collisions challenges our conventional wisdom on the formation of the quark-gluon plasma (QGP). A microscopic explanation to the origin of collectivity in pp collisions will help us understand the mechanism that leads to the QGP-like signals in small systems. In our recent work [1,2], we have...
Proton-lead collisions at LHC energies offer unique possibilities to investigate the nuclear modifications of parton distribution functions (PDF) over a wide kinematic range. In this talk, we will present measurements of the dijet per-event yields at center-of-mass energy 8.16 TeV in $p$+Pb collisions. The per-event yields of unfolded dijet pairs will be presented in terms of kinematic...
The study of inclusive jet and dijet production in small (pp and p--Pb) collision systems is essential to probe the initial state of the collision, constrain PDFs, test pQCD predictions and probe cold nuclear matter (CNM) effects. In addition, recent studies at high multiplicity in small collision systems exhibit signatures of collectivity typically associated with the color-deconfined matter...
The sPHENIX detector at the BNL Relativistic Heavy Ion Collider (RHIC) uses the combination of electromagnetic calorimetry, hermetic hadronic calorimetry, precision tracking, and the ability to record data at high rates without trigger bias to make pioneering measurements of jets, jet substructure, and jet correlations. Jet observables are a particularly useful probe of the Quark Gluon Plasma...
We study the jet quenching parameter $\hat q$ at the initial pre-equilibrium stages of heavy-ion collisions using the effective kinetic theory description of the anisotropic quark-gluon plasma. This allows us to smoothly close the gap in the literature between the early glasma stage of the collision and the onset of hydrodynamics. We find that the bottom-up evolution of $\hat q$ shows little...
Constraining the properties of the quark--gluon plasma (QGP) depends heavily on our understanding of all phases of heavy-ion collisions. An important advancement has been the definition of symmetric cumulants (SC), which have been shown to be very sensitive to the transport properties of the QGP. Since the SC measurements of lower-order flow harmonics provided more information about the...
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,...
Studies of longitudinal de-correlation of anisotropic flow can provide unique constraints on the three-dimensional structure of the initial state and dynamical evolution of the quark-gluon-plasma in heavy-ion collisions. Experimentally, the factorization ratio, $r_{n}(\eta)(n = 2,3)$, is used to quantify the amount of the longitudinal flow de-correlation with pseudorapidity [1-3]. With data...
This talk presents a measurement of longitudinal decorrelation in $pp$ collisions with ATLAS. It is expected that the deposited energy in the transverse $(x,y)$ plane varies, 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...
Heavy quarks are produced in hard partonic scatterings at the very early stage of heavy-ion collisions and they experience the whole evolution of the created Quark-Gluon Plasma medium. Femtoscopic correlations, i.e., two-particle correlations at low relative momentum, are sensitive to the final-state interactions and the extent of the region from which correlated particles are emitted. A study...
This talk presents a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive-charged particle yields in 13 TeV pp collisions. Measurements are made deferentially for Upsilon momentum and for different Upsilon states. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV pp...
sPHENIX will start data taking in Spring 2023 at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The sPHENIX detector will enable a spectrum of new or improved cold QCD measurements, enhancing our understanding of the initial state for nuclear collisions. sPHENIX measurements in proton-proton and proton-nucleus collisions will reveal more about how partons behave...
Multiparton interactions in proton-proton collisions have long been a topic of great interest. A new look at them has begun to emerge from work being done to understand the dynamics of ‘small systems’, a topic that is taking center stage in the physics of relativistic heavy-ion interactions. Numerous studies conducted at the LHC and lower energies reveal that proton-proton collisions at high...
Measurements by CMS have provided evidence for the collective behavior of multiparticle production in high-multiplicity proton-proton (pp) and proton-lead (pPb) collisions at the LHC. Although this collectivity aligns with the notion of a hydrodynamic flow origin, it is also possible to interpret it in relation to initial-state correlations caused by, for example, gluon saturation. To...
The PHENIX experiment pioneered measurements of nuclear modification
factor of neutral pions and photons, providing strong evidence
of the formation of Quark-Gluon Plasma (QGP) in Au+Au collisions
at RHIC. In 2014 large amount of 200 GeV Au+Au data were collected,
vastly exceeding the statistics of all similar data taken earlier.
This makes it possible to extend the transverse momentum...
The measurement of neutral mesons in pp and p—Pb collisions allows for testing perturbative QCD calculations, and provides an important baseline for heavy-ion measurements. The combination of the different reconstruction methods in ALICE allows the measurements of neutral mesons in a very wide range of transverse momenta, and thus imposes restrictions on the parton distribution functions and...
Measurements of quarkonia production in peripheral and ultra-peripheral heavy-ion collisions are sensitive to photon-photon and photon-nucleus interactions, the partonic structure of nuclei, and to the mechanisms of vector-meson production. In this contribution, recent measurement performed by LHCb will be presented, such as the coherent and incoherent production of $J/\psi$ mesons in...
In the context of relativistic heavy-ion collisions at high beam energies, we investigate the fate of the field perturbations for the second order Israel-Stewart-type hydrodynamics on top of the boost-invariant attractor background. In particular, we analyze both the early-time and late-time asymptotic behavior of these hydrodynamic perturbations at different spatial scales. Our findings...
Ultraperipheral heavy ion collisions provide the first opportunity to study collisions between photons and heavy ions in high-energy colliders. In these collisions the beam particles have a large impact parameter such that no hadronic interactions occur but a low-virtuality photon emitted by a beam particle may collide with a particle from the other beam. Several recent experimental analyses...
The development of a TeV-scale muon accelerator and storage ring provides enormous scientific potential not only for a mu+mu- collider, but also for deep inelastic scattering (DIS) in a completely new regime when a TeV muon beam is collided with a hadron beam. In this talk, we will introduce the concept of a muon-ion collider (MuIC) that can be realized by leveraging the approved electron-ion...
We use QCD kinetic theory to compute photon 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 production on the kinetic and chemical equilibration time. This allows us to...
Constraining the initial condition of the QGP using experimental observables is one of the most important challenges in our field. Recent studies show that both $\rho_n(v_n, [p_\mathrm{T}])$ (correlation between $v_n$ and event-wise mean $p_\mathrm{T}$) and $[p_\mathrm{T}]$ fluctuations can probe several ingredients of the initial state, such as number and size of sources, volume fluctuation,...
It is a fundamental question to understand what is the effective carrier of conserved quantum charges inside a proton at high energy. The net baryon and electric charged rapidity distributions in relativistic heavy-ion collisions can elucidate how different flavors of conserved charges are transported along the longitudinal direction during the collisions. Recent isobar collisions at the...
The shape of atomic nuclei is described by a multipole expansion of the parton distribution function. Most nuclies generally have intrinsic deformation, where the quadrupole moment carries the most significant contribution. The shape of a quadrupole deformed nuclies is described by the deformation strength $\beta_2$, and an axial symmetry component $\gamma$. In ultra-relativistic heavy-ion...
Thanks to the injection of noble gases in the LHC beam-pipe while proton or ion beams are circulating, the LHCb spectrometer has the unique capability to function as the highest-energy fixed-target experiment ever built. The resulting beam+gas collisions cover an unexplored energy range that is above previous fixed-target experiments, but below the top RHIC energy for AA collisions. In this...
We aim to probe the early stages of high-energy nuclear collisions using heavy quarks (HQs). The pre-equilibrium stage of relativistic heavy-ion collisions, commonly known as Glasma, evolves according to the classical Yang-Mills (CYM) equations. We study the transverse momentum broadening $\sigma_p$ of HQs in the evolving Glasma using relativistic kinetic theory. We observe that $\sigma_p...
Neutron skin thickness $\Delta r_{\rm np}$ of nuclei and the inferred nuclear symmetry energy are of critical importance to the equation-of-state of dense nuclear matter in neutron stars and heavy-ion collisions. The $\Delta r_{\rm np}$ has traditionally been measured by low-energy hadron-nucleus and nucleus-nucleus scatterings over decades.Recent studies indicate that the neutron skin can...
We study nonequilibrium dynamics of SU(2) lattice gauge theory in Minkowski space-time in a classical-statistical regime, where characteristic gluon occupancies are much larger than unity. In this strongly correlated system far from equilibrium, the correlations of energy and topological densities show self-similar behavior related to a turbulent cascade towards higher momentum scales. I...
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...
Suppression of open heavy flavors and quarkonia in heavy-ion collisions is among the most informative probes of the quark-gluon plasma. 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,...
One of the major upgrades to ALICE for LHC Run 4 is the Forward Calorimeter (FoCal). This calorimeter comprises two sections, an Electromagnetic Calorimeter (FoCal-E) and a Hadronic Calorimeter (FoCal-H). Among the physics goals for FoCal is the study of physics at low-x, a regime in which one expects to see signals related to the gluon density in the initial nucleons which form the initial...
We explore the effect of the Glasma fields, which are used to describe the very-early stage of heavy-ion collisions, on the dynamics of heavy quarks and jets. We achieve this through numerical simulations of the strong fields, done using classical lattice gauge theory, which are then used as background for the propagation of classical particles. Based on the colored particle-in-cell method, we...
In this talk, we present numerical results on diffractive dissociation of virtual photon in the scattering off hadron. The calculation employs the dipole picture of diffractive deep inelastic scattering and solutions to nonlinear Kovchegov-Levin equation, taking into account the running coupling correction and a simple treatment of impact parameter dependence. The (modified)...
We study the single-inclusive particle production from proton-nucleus collisions in the dilute-dense framework of the color glass condensate (CGC) at next-to-leading order (NLO) accuracy. In this regime, the cross section factorizes into hard impact factors and dipole-target scattering amplitude describing the eikonal interaction of the partons in the target color field. We combine, for the...
We simulate the space-time dynamics of high-energy collisions based on a microscopic kinetic description in the conformal relaxation time approximation, in order to determine the range of applicability of an effective description in relativistic viscous hydrodynamics [1,2]. We find that hydrodynamics provides a quantitatively accurate description of collective flow when the average inverse...
The pseudorapidity densities of charged particles and inclusive photons produced in high-energy nuclear collisions are essential observables to characterise the global properties of the collisions, such as the achieved energy density, and to provide important constraints for Monte Carlo model calculations. In the LHC Run 1 and Run 2 configurations, ALICE had large coverage to measure charged...
The numerical computation of real-time observables in quantum field theories is a longstanding challenge, largely due to the infamous sign problem. While complex Langevin (CL) has emerged as a promising method to address this issue, its stability and convergence properties are problematic for certain physical systems. In this talk, I present our recent advances in applying CL to SU(2) lattice...
Data obtained at RHIC can be reproduced with relativistic viscous hydrodynamic simulations by adjusting the viscosity and initial conditions but it is difficult to disentangle these quantities. It is therefore important to find orthogonal observables to constrain the initial conditions separately from the viscosity. New observables have been measured at the LHC and shown to be sensitive...
We present a full set of the Boltzmann Equation in Diffusion Approximation (BEDA) for studying thermal equilibration of quarks and gluons. Using BEDA, we first analyse thermalization and quark production of spatially homogeneous systems initially populated by gluons. We observe that soft partons, dominantly produced via medium-induced radiation, rapidly fill a thermal distribution with an...
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 is 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...
In relativistic heavy-ion collisions, the final state collectivity is characterized by the anisotropic flow, measured through flow vector estimations. Hydrodynamics calculations and experimental data show that the flow vector fluctuates as a function of particle transverse momenta event-by-event, indicating fluctuations in the initial energy density of the nuclear collisions. In heavy-ion...
Two-particle transverse momentum correlations enable measurements of the collision dynamics sensitive to momentum currents. Their evolution with collision multiplicity, as proxy of the system lifetime, gives information about the specific shear viscosity, $\eta/s$, and the system relaxation time, $\tau_{\pi}$.
In this talk, measurements of two-particle transverse momentum correlators in pp,...
Measurements of correlations between different symmetry planes in ultrarelativistic heavy-ion collisions probe the initial state and non-linear hydrodynamic response of the medium to initial anisotropies. Earlier studies on symmetry plane correlations (SPC) were conducted by using the Scalar Product method. However, this method is biased by the presence of correlations between different flow...
