After getting two remarkable scientific upgrades of quark-gluon plasma (QGP) physics - lowest viscous nature and strong magnetic field production, viscous properties of QGP in a strong magnetic field become one of the important matters of research. Instead of one isotropic shear viscosity, as we get in absence of magnetic field, five different components of shear viscosity ${\tilde\eta}_n...
Yufu Lin (for the STAR collaboration)
The chiral magnetic effect (CME) is a novel transport phenomenon, arising from the interplay between quantum anomalies and strong magnetic fields in chiral systems.
In high-energy nuclear collisions, the CME may survive the expansion of the quark-gluon plasma fireball and be detected in experiments. Over the past two decades, the experimental...
I discuss effects of strong magnetic fields on the photon propagation in vacuum. I elaborate on the mechanism that leads to the vacuum birefringence and the vacuum dichroism, putting an emphasis on the fermion spectrum in magnetic fields and showing explicit diagrammatic computation. I also mention potential experimental feasibility with the strong magnetic field induced by the ultraperipheral...
We derive semiclassical spin statistical mechanics in Riemann geometry with an external torsion field and use it to investigate spin hydrodynamics and chiral effects. We derive spin hydrodynamics with torsion at the first order of gradients in local equilibrium state. We show torsion plays a similar role as vorticity in spin hydrodynamics and induces spin polarization in equilibrium state. In...
In heavy-ion collisions, a strong magnetic field ($\sim$ 10$^{15}$ T) is expected to be created, which in the presence of a non-zero electric and axial charge density, can lead to vector and axial currents in the produced system $\textendash$ the phenomena called the Chiral Magnetic Effect (CME) and Chiral Separation Effect (CSE), respectively. Their coupling gives rise to a collective...
High energy heavy ion collisions at the LHC generate extreme magnetic field reaching $10^{14}$ T~$10^{15}$ T when heavy ions cross each other at almost the speed of light in peripheral collisions. The intensity of this generated magnetic field is much higher than the critical magnetic field of electrons, $4×10^9$ T, and various nonlinear behaviors such as real photon decay are expected in the...
Event-by-event fluctuations measured in the heavy-ion observables such as the flow coefficients and their correlations play an important role in extracting the matter properties. While the major origin of the observed flows are the initial fluctuations, other sources of the fluctuations become also important in smaller systems and in the quantitative determination of the matter...
Hydrodynamic expansion and jet quenching are responsible for the production of low and high transverse-momentum ($p_T$) particle in heavy-ion collisions, respectively. However, it is still a challenge to simultaneously describe hadron nuclear modification factor RAA and elliptic flow $v_2$, especially in the intermediate pT region of 2<$p_T$<10 GeV/c. In this talk, besides hydrodynamics and...
Hydrodynamics-based frameworks have been developed as powerful tools to extract properties of the quark-gluon plasma (QGP) from experimental data of relativistic heavy-ion collisions at RHIC and LHC. Although significant developments have been made so far, hydrodynamics-based frameworks still have open issues to be resolved. First, energy and momentum of incoming nuclei are not respected in...
The fate of a perturbation (disturbance) imparted in the QGP fluid governed by the second-order Israel-Stewart viscous hydrodynamics has been studied when it passed through the Critical End Point (CEP). The effects of CEP have been incorporated in the system through the Equation of State (EoS). The dispersion relation for the perturbation in frequency ($\omega$) wave vector ($k$) space has...
Light-nuclei production is one of the hot topics in heavy-ion collisions for the high-baryon-density region of the QCD phase diagram. It was found to exhibit a non-monotonic behavior with respect to the colliding energy in experiments and thus was suggested to be a possible signal of the QCD critical point.
This talk introduces a systematic expansion of the light-nuclei production within...
The primary goal of the ultrarelativistic heavy-ion collision program at the LHC is to study the quark-gluon plasma (QGP) properties, a state of strongly interacting matter that exists at high temperatures and energy densities. However, the lack of knowledge on the initial conditions of heavy-ion collision results in a significant uncertainty of the extraction of the transport properties of...
We discuss multi-charmed and exotic hadrons in heavy ion collisions by focusing on their production based on both the statistical and coalescence models. Starting from the investigation on estimated yields of multi-charmed hadrons in the statistical hadronization model, we consider transverse momentum distributions of those hadrons produced at quark-hadron phase transition in the coalescence...
The production cross sections of open heavy-flavour hadrons can be obtained by the collinear factorisation approach of QCD, by means of a convolution of the initial parton distribution functions of the incoming partons, the perturbative QCD partonic cross section, and the fragmentation functions in $\mathrm{e^+e^-}$, ep collisions. Recent measurements of charm-baryon production at midrapidity...
In this talk, we will discuss how sensitive is the heavy quarkonia to the bulk viscous nature of the QGP medium. We will discuss the effects of bulk viscous correction on the properties of quarkonium states. The non-equilibrium bulk viscous correction is incorporated in the distribution functions of thermal quarks and gluons, with which we compute the dielectric permittivity within the hard...
The goal of the ALICE experiment is to investigate the quark-gluon plasma (QGP), a state of matter in which quarks and gluons are deconfined. Heavy quarks, charm and beauty, are efficient probes of the properties of the QGP since they are predominantly produced in initial hard scattering processes, and subsequently interact with the medium. In particular, beauty production can be utilized to...
Quarkonia is a very useful tool to study the properties of the hot, dense matter, quark-gluon-plasma (QGP) in various collision systems. In this talk, we will review the recent results of the elliptic flow parameter (v2) of Upsilon(1S) and Upsilon(2S) mesons in PbPb collisions. Also, we present the cross-sections and nuclear modification factors of Psi(2S) and bottomonia in pPb collisions to...
Transverse momentum broadening and energy loss of a propagating parton are dictated by the space-time profile of the jet transport coefficient $\hat q$ in dense QCD medium. Spatial gradient of $\hat q$ perpendicular to the propagation direction can lead to a drift and asymmetry in parton transverse momentum distribution. Such an asymmetry depends on both the spatial position along the...
Dijet production in proton-nucleus ($p$A) collisions at the LHC provides invaluable information on the underlying parton distributions in nuclei, especially the gluon distributions. Triple-differential dijet cross sections enable a detailed kinematic scan (over momentum fraction $x$ and probing scale $Q^2$) of the nuclear parton distribution functions (nPDFs), i.e., $f^\textrm{A}_i(x,Q^2)$....
The phase transition from hadronic matter to quark-gluon plasma (QGP) is a phenomenon that occurs under extreme conditions of high temperature and high density. The QGP causes energy loss of high momentum particles which is observed as suppression of high momentum hadron production in A+A collisions relative to p+p collisions. PHENIX, one of the relativistic heavy ion collider (RHIC)...
We investigate the real time evolution of a highly occupied and weakly coupled Yang-Mills field in the expanding geometry using the semiclassical approximation, and study its thermalization in terms of the Husimi-Wehrl(HW) entropy that is defined by the Husimi function. The initial conditions are given to mimic the realistic grasma initial condition, where the color electric and color magnetic...
We analyze the chemical equilibration by computing relaxation time of a gas of the SU(3) octet of pseudoscalar mesons at finite temperature and zero baryon chemical potential [1]. The amplitudes of all possible reactions in the system have been taken from next-to-leading-order chiral perturbation theory. The amplitudes are further unitarized using inverse amplitude method to calculate the...
Based on the fact that the mass difference between the chiral
partners is an order parameter of chiral phase transition and that
the chiral order parameter reduces substantially at the chemical
freeze-out point in ultra-relativistic heavy ion collisions, we
argue that the production ratio of 𝐾1 over 𝐾∗ in such
collisions should be substantially larger than that predicted in
the...
Hadronic resonances are very useful to probe the late-stage evolution of ultra-relativistic nucleon-nucleon or nuclear collisions. Since they have lifetimes comparable to the hadronic phase timespan, rescattering and regeneration processes may affect the measured yields. These processes modify the resonance momentum distributions. Measurements of the differential yields of resonances with...
High-energy heavy-ion collisions, a branch of nuclear physics that focus on study of quark-gluon plama (QGP) and nuclear phase diagram, have always assumed an initial condition from the nuclear structure physics, e.g. the Woods-Saxon geometry. Recent progress in hydrodynamic modeling together with the wealth of precision collective flow data, especially from the Isobar collisions, however,...
Collective phenomena in heavy-ion collisions are very sensitive to initial geometry including nuclei deformation effects. In the hydrodynamic model description of heavy ion collisions, the final-state anisotropic flow $v_n$ are linearly related to the strength of the multi-pole shape of the nucleon density distribution in the transverse plane $\epsilon_n$, $v_n \propto \epsilon_n$. The...
We systematically study the hyperon global polarization's sensitivity to the collision systems' initial longitudinal flow velocity in hydrodynamic simulations. By explicitly imposing local energy-momentum conservation when mapping the initial collision geometry to macroscopic hydrodynamic fields, we study the evolution of systems' orbital angular momentum (OAM) and fluid vorticity. We find...
Non-central heavy-ion collisions produce a large angular momentum that leads to vorticity of the created system.
Due to the spin-orbit coupling, spin directions of particles are aligned with the orbital angular momentum of the system.
Global polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons has been measured in Au+Au collisions from $\sqrt{\rm{s_{NN}}}$ = 7.7 GeV to 200...
We report the first measurement of the rapidity-odd directed flow ($v_1$) of multi-strange baryons ($\Xi$ and $\Omega$) in Au+Au collisions as recorded by the STAR detector at the Relativistic Heavy Ion Collider.
We focus on particle species where all constituent quarks are produced, as opposed to possibly transported, and demonstrate using a novel analysis method that the coalescence sum...
Collective flow has been commonly used for studying the properties of matter created in high-energy heavy-ion collisions, due to its high sensitivity on early stage collision dynamics. The first-order Fourier coefficient of azimuthal distributions of produced particles $v_1$, also called directed flow, has been analyzed for different particle species from the lightest mesons to light nuclei in...
In this talk, we will present the recent results on two-particle correlations in high-multiplicity pp collisions at $\sqrt{s}=$~13~TeV and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$~5.02~TeV from the ALICE Collaboration. The origin of long-range modulations remains an open question, and can be indicating collective dynamics in both small and large systems. We will present recent...
Transport theory can extract microscopic information in heavy-ion collisions of low-energy region. Though many transport codes have been emerged in recent years, there is not any codes optimized for Korean HIC acclerator. We initiated a new project so called DJBUU project with easy handling in order to prepare experiments in Rare isotope Accelerator complex for ON-line experiments (RAON). One...
Quarks are confined inside a hadron as a color-neutral composite particle. Quantum chromodynamics (QCD), the fundamental theory of strong interactions, does not rule out an existence of exotic hadrons other than mesons and baryons. However, a dibaryon consisting of six quarks has not yet been discovered. The discovery of dibaryons would lead to a deeper understanding of QCD. In particular,...
The interaction between hyperon-hyperon (Y-Y) is not well understood theoretically and experimentally.
The Y-Y interaction is important to understand the EOS of neutron star interior as well as to search for exotic hadrons such as H-dibaryon.
The H-dibaryon was proposed as a stable six-quark state resulting from combination of two $¥Lambda$ hyperons. According to the lattice QCD...
Higher-order cumulants and their ratios of the conserved quantities are powerful tools used to understand the QCD phase diagram. They are sensitive to the phase structure and the correlation length of the medium created in the collisions. Non-monotonic energy dependence of fourth-order cumulant of net-proton multiplicity distributions has been reported by the STAR Collaboration. In addition,...
One of the key ingredients in hadron physics based on QCD is the notion of diquark correlations, which in turn could lead to the color superconductivity (CSC) in dense and cold quark matter with a Fermi surface to be realized in a compact star. One of the main focuses of recent experiments using heavy-ion collision is to reveal possible rich physics in high baryon-density matter at relatively...
Dileptons and photons are unique tools to study the space-time evolution of the hot and dense matter created in ultra-relativistic heavy-ion collisions. Their main sources are hard QCD processes (prompt photons), thermal production and semi-leptonic heavy-flavour decays. They carry undistorted information about the various stages of the collision as they are either produced at early times...
Different orientations of collisions of $\alpha$-clustered carbon with a heavy ion can produce significantly large initial-state anisotropies due to the intrinsic geometry effects of the carbon. We expect that such large initial-state anisotropies have a profound impact on the photon flow observables. We calculate the transverse momentum spectra and anisotropic flow coefficients of thermal...
Electromagnetic probes are one of promising tools to investigate properties of the hot and dense matter created in high-energy heavy-ion collisions. However, state-of-the-art phenomenological models which can correctly explain spectra and anisotropic flows of charged particles underpredict yield and elliptic flow of photons. It is known as “photon puzzle”.
Here we propose photon emission...
LAMPS experiment is designed to research various physics topics in heavy ion physics, Symmetry energy, Collective flow, Mirror nuclei ratio, Dipole emission, etc.
LAMPS group developed and construct detectors for LAMPS experiment for several years.
RAON, the first laboratory for heavy ion physics research in Korea, is about to end its 1st step construction in 2021.
LAMPS experiment is...
The primary goal of the ultrarelativistic heavy-ion collision program at the LHC is to study the quark-gluon plasma (QGP) properties, a state of strongly interacting matter that exists at high temperatures and energy densities. However, the lack of knowledge on the initial conditions of heavy-ion collision results in a significant uncertainty of the extraction of the transport properties of...
