Relativistic heavy-ion collisions offer a unique opportunity to probe the deformation of colliding nuclei. The quadrupole deformation parameter $\beta_{2}$ has been extensively studied through the flow coefficient $v_2$ in such collisions, as well as through low-energy measurements of the electric quadrupole transition probabilities, $\rm B(E_{2})$. In contrast, the hexadecapole deformation...
Chiral matter exhibits a variety of intriguing anomalous transport phenomena that originate from the chiral anomaly. Prominent examples of such phenomena include the chiral magnetic effect and the chiral vortical effect. In the hydrodynamic regime, we demonstrate that in a chiral plasma subject to an external magnetic field, the chiral vortical effect can induce a new type of...
Heavy quarks are produced in hard scatterings at the very beginning of a heavy-ion collision. As a result, they experience all subsequent stages of the collision, and their dynamics are particularly sensitive to the properties of the quarkโgluon plasma (QGP) phase. Recent studies have demonstrated that a fluid-dynamical description of heavy-quark transport in the QGP, combined with a realistic...
The medium produced at RHIC Beam Energy Scan (BES) energies is baryon-rich. This enhanced baryon stopping not only leads to a splitting in the yields of baryons and anti-baryons, but has also been observed experimentally to produce a splitting in their flow coefficients. Hydrodynamic models have struggled to reproduce this baryon-antibaryon flow splitting with the correct magnitude and sign,...
Recent experimental observations of collective-like phenomena in small collision systems, such as pp collisions, have challenged traditional paradigms and highlighted the critical role of initial-state geometry and its fluctuations. In particular, longitudinal decorrelations serve as a powerful probe of the three-dimensional initial-state structure and longitudinal dynamics of the collision...
We systematically investigate the scaling properties of the transverse momentum spectra for pions, kaons, and protons in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, as well as in U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV, across different centrality classes, using experimental data from the collaborations at the Relativistic Heavy Ion Collider...
Radial flow is conventionally studied through transverse-momentum ($p_{T}$) spectra and blast-wave model analyses, which provide information on the average collective expansion and kinetic freeze-out properties of the system. In contrast to the extensively studied anisotropic-flow coefficients $v_{2}$ and $v_{3}$, the $p_{T}$-differential fluctuations of radial flow remain largely unexplored....
Directed flow ($v_1$) and elliptic flow ($v_2$) provide complementary probes of the equation of state, degrees of freedom, and collective dynamics of the produced medium. Here, we present STAR measurements of collective flow for identified strange and multistrange hadrons in heavy-ion collisions at RHIC.
Using high-statistics data from the STAR Beam Energy Scan Phase-II (BES-II)...
Relativistic heavy-ion collisions provide a unique avenue to image nuclear structure by converting initial spatial geometry into the collective expansion of the Quark--Gluon Plasma (QGP). While the quadrupole deformation ($\beta_2$) sits at the center of this paradigm as the primary driver of initial geometry, a complete understanding of nuclear shape requires extending this framework to...
The thickness of the neutron skin ($\Delta r_{np}$) in $^{48}$Ca remains uncertain, with parityโviolating electron scattering (CREX) and ab initio calculations favoring a thin skin while energy density functionals prefer larger values. Heavyโion collisions at relativistic energies can probe the skin through its geometric imprint on the quarkโgluon plasma, but a thicker skin also increases the...
The triangular flow coefficient ($v_{3}$) is the third term in the Fourier expansion of the azimuthal distribution of particles produced in heavy-ion collisions. A non-zero $v_{3}$ arises from event-by-event fluctuations in the positions of participant nucleons within the collision zone. Higher order flow coefficients, particularly $v_{3}$ and higher harmonics, exhibit enhanced sensitivity to...
We analyze the effects of the magnetic field on the quark and gluon propagators within the functional QCD framework. By solving the coupled DysonโSchwinger equations for the quark and gluon propagators, we find that the quark mass is generally enhanced in the presence of a magnetic field, leading to magnetic catalysis of the chiral condensate. Meanwhile, the magnetic field also induces an...
In heavy-ion collisions, collective flow arises from the response of the produced medium to the initial-state geometry. Measurements of azimuthal particle correlations provide powerful tools to investigate the emergence of collective behaviour, the transport properties of hot QCD matter, and the role of nuclear geometry in the initial state. The LHCb experiment offers unique capabilities for...
We investigate the applicability of hydrodynamics in small collision systems by comparing viscous anisotropic hydrodynamics (VAH) with conventional viscous hydrodynamics (VH). In $\sqrt{s}=13$ TeV p+p collisions, VAH successfully describes $v_2\{2\}$, $v_3\{2\}$, and the negative $c_2\{4\}$, whereas VH requires evolution characterized by large shear Knudsen numbers. We further compare VAH and...
A central question in strong-interaction physics, governed by quantum chromodynamics (QCD), is whether femto-scale droplets of quarkโgluon plasma (QGP) form in small collision systems involving projectiles significantly smaller than heavy ions. Collisions of light ions such as 16O and 20Ne offer a unique opportunity to probe the emergence of collective behavior in QCD matter. This work...
Relativistic $^{16}$O+$^{16}$O collisions provide a valuable opportunity to study both the quark-gluon plasma formed in small systems and the intrinsic structure of $^{16}O$. Recent implementations of ab initio nuclear configurations in heavy-ion simulations have produced different predictions for cluster-sensitive observables, making it difficult to identify the origin of possible ๐ผ-cluster...
Ultracentral nucleusโnucleus collisions provide a uniquely stringent test of fluctuating initial conditions: although their average transverse geometry is nearly azimuthally symmetric, measurements reveal an unexpected near degeneracy of elliptic and triangular flow, whereas conventional hydrodynamic calculations generally predict (v_2{2}>v_3{2}). An independent challenge is posed by the...
Strangeness production is a sensitive probe of quark-gluon plasma formation and of how it varies with collision-system size. In central heavy-ion collisions at both RHIC and LHC, significant $\Omega$/$\phi$ ratio enhancement with relation to peripheral collisions has been observed at intermediate transverse momentum. It is also reported by ALICE that the strange-hadron-to-pion yield ratios...
The longitudinal structure of the quarkโgluon plasma (QGP) is the missing third dimension in our picture of its initial state. It records how energy is deposited along the beam, how quantum fluctuations in the colliding nuclei shape the plasma, and how collective expansion converts this geometry into final-state momentum correlations. Accessing it is notoriously difficult: short-range nonflow...
Nuclear structure theory provides point-nucleon densities, whereas high-energy nuclear collisions probe nuclei through finite-resolution hadronic interactions. When point densities are used as nucleon-center distributions in Monte Carlo initial-state models, varying the nucleon width changes both the interaction range and the folded nuclear surface. This resolution mismatch obscures the...
For dijet production in deeply inelastic scattering, photon-quark scattering is important at large x, while photon-gluon fusion becomes important toward smaller x. In the large-x regime, the energetic parton
undergoes multiple scattering and gluon radiation in a large nucleus (jet quenching), where LPM interference can be observed [Y. Y. Zhang and X. N. Wang 2022]. In the small-x regime, the...
We compute the time evolution of the quarkonium density matrix in the background glasma field, the primordial state of matter in relativistic heavy-ion collisions, and show how the color of the quarkonium state is randomized. This color randomization is of particular interest because it drives the quarkonium out of its color-singlet state, leading to dissociation. The resulting suppression of...
We introduce MC-CGC, a new event generator built on the saturation description of particle production in pp and p(d)+A collisions. The framework incorporates radiation, realistic soft production, beam remnant treatment, and fragmentation, and is calibrated against data across multiple systems and different collision energies. Our main predictions focus on the transverse-momentum spectra and...
Hydrodynamic models fail to describe the near-equal $v_3 / v_2$ ratio observed in ultra-central heavy-ion collisions, despite their success in other centrality classes. This
failure can not be resolved by adjusting the shear viscous coefficient, as shear viscosity suppresses higher-order anisotropic flows more strongly, leading to an underestimation of $v_3$ when $v_2$ matches experimental...
In relativistic heavy-ion collisions, quasireal photons are highly linearly polarized, giving rise to characteristic azimuthal correlations in vector-meson decays. In ultra-peripheral collisions, the spin-interference effect can be quantified through the azimuthal modulation between the $J/\psi$ transverse momentum and its decay-lepton axis, providing sensitivity to the transverse spatial...
Polarization and spin alignment have emerged as important tools for investigating the dynamical properties of the strongly interacting matter produced in relativistic nuclear collisions. Spin-dependent observables provide access to different aspects of the collision depending on the particle species and the choice of the spin-quantization axis. Correlations with the event or reaction plane can...
Hyperon spin correlations have recently attracted significant interest as a probe of QCD spin dynamics. A recent theoretical study suggests that the spin correlation for ฮ hyperon pairs is a sensitive probe to separate strong-force-field-induced vector meson spin alignment from hydrodynamic effects, and to probe spin-orbit coupling, polarization transfer, and possible spin entanglement in...
An autoregressive neural sampler writes a lattice configuration site by site, each site conditioned on the sites already written, and it returns independent samples with an exact likelihood. Each conditional sees only a context window of fixed reach, and nothing in the architecture says how far that reach has to extend.
Set the reach one unit short of what the target needs and the interior...
