### Conveners

#### Collective dynamics: I

- Ulrich Heinz (The Ohio State University)

#### Collective dynamics: II

- Raimond Snellings (Nikhef National institute for subatomic physics (NL))

#### Collective dynamics: III

- Steffen A. Bass (Duke University)

#### Collective dynamics: IV

- Tetsufumi Hirano (Sophia Univ)

Anisotropic flow is a key observable to characterize the system created in heavy-ion collisions, as it is sensitive to its initial state, transport properties, the equation of state and freeze-out conditions. In this presentation, we present the anisotropic flow coefficients of inclusive charged particles in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 and 5.02 TeV, and Xe-Xe collisions at...

Valuable information about the behavior of a heavy-ion collision system can be obtained by changing the species of colliding nuclei, and in particular using species of different size. This change in system size can probe characteristic behavior in a way that is not possible with a single collision system. Already, results of small collisions systems such as p-p, p-A, d-A, and $^3$He have...

The elliptic and higher-order azimuthal anisotropy Fourier harmonics ($v_n$) are obtained for pPb collisions at $\sqrt{s_{NN}} = 8.16$ TeV over a wide range of event multiplicities based on multiparticle correlations. The data were collected by the CMS experiment during the 2016 LHC run. A sample of peripheral PbPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV covering a similar range of event...

Precise measurements of higher-order coefficients of anisotropic flow ($v_n$, $n>3$) are now available in Pb+Pb data collected at the Large Hadron Collider. Higher-order coefficients are interesting because they do not simply originate as a response of the medium to its initial geometry, but rather from an intricate nonlinear coupling of harmonics of lower order. Hence, they serve as a...

The recently proposed symmetric cumulants and non-linear flow mode coefficients provide new observational probes to study initial conditions and microscopic transport properties of the quark-qluon plasma (QGP) formed in heavy-ion collisions. Comparison of such measurements with viscous hydrodynamic calculations should, in particular, enable the study of the temperature dependence of the shear...

We establish a set of equations for moments of the distribution function. On the one hand, these equations generalize the fluid dynamics to the out-of-equilibrium evolution of boost invariant plasmas. On the other hand, they systematically generalize the theoretical framework of viscous hydrodynamics to arbitrary orders. These moments quantify details of the momentum anisotropies of...

The experimental data collected by the ATLAS experiment during the 2015 Pb+Pb and 2017 Xe+Xe LHC runs offer new opportunities to study charged particle azimuthal anisotropy. The high-statistics Pb+Pb sample allows for a detailed study of the azimuthal anisotropy of produced particles. This should improve the understanding of initial conditions of nuclear collisions, hydrodynamical behavior of...

The azimuthal anisotropies of particle spectra measured in proton-nucleus (pA) and nucleus-nucleus (AA) collisions play a key role in constraining QCD matter properties like the shear viscosity over entropy density ratio eta/s. We compare calculations of v_n’s from viscous fluid dynamics and from kinetic transport which start both from the same initial conditions and which implement the same...

New measurements of collective flow in XeXe collisions at a center-of-mass energy of 5.44 TeV per nucleon pair, collected by the CMS experiment at the LHC, are presented. The $v_{2}$, $v_{3}$ and $v_{4}$ Fourier coefficients of the anisotropic azimuthal distribution are obtained employing three different analysis techniques: two-particle correlations, scalar product method and multiparticle...

Microscopic transport approaches are the tool to describe the non-equilibrium evolution in low energy collisions as well as in the late dilute stages of high energy collisions. In this talk, a newly developed hadronic transport approach, SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is introduced. After explaining all the components of this approach, e.g. initial conditions...

The measurement of the decorrelation of flow harmonics, $v_n$, and event plane angles, $\Psi_n$, (or flow vector, $V_n\equiv v_ne^{in\Psi_n}$) in the longitudinal direction explores the non-boost-invariant nature of the initial collision geometry and final state collective dynamics. The decorrelations were first observed at the LHC, but are predicted by several (3+1)D hydrodynamic models to be...

At Relativistic Heavy Ion Collider (RHIC) Beam Energy Scan (BES) energies, the dynamics of the pre-equilibrium stage and the effects resulting from a nonzero net baryon current become critical components of the dynamical evolution of the collision fireball. We develop a (3+1)-dimensional hybrid evolution model with dynamical sources for both energy-momentum and the net baryon current. During...

We present a fully three-dimensional model providing initial conditions for energy and conserved charge density distributions in heavy ion collisions at RHIC Beam Energy Scan (BES) collision energies [1,2]. The model includes the dynamical deceleration of participating nucleons or valence quarks. It provides a realistic estimation of the initial baryon stopping during the early stage of...

Directed flow ($v_1$) is a good probe of the early-stage dynamics of collision systems, and the $v_1$ slope ($dv_1/dy$) at mid-rapidity is sensitive to the system's equation of state. Previously, a coalescence picture has been used to relate the elliptic flow ($v_2$) of identified particles to the $v_2$ of their constituent quarks [1]. In this talk, the coalescence idea is extended to study...

Disentangling the effect of initial conditions and medium properties is an open question in the field of relativistic heavy-ion collisions. We argue that, while one can study the impact of initial inhomogeneities by varying their size, it is important to maintain the global properties fixed.

We present a method to do this by systematically smoothening the initial conditions, and apply it to...

In this talk, we will present phenomenological predictions of 3+1d quasiparticle anisotropic hydrodynamics (aHydroQP). First, we will show comparisons with experimental data produced in 2.76 TeV Pb-Pb collisions at the LHC (PRL 119, 042301 and PRC 96, 044910). We will show some observables such as the spectra, multiplicity, elliptic flow, and HBT radii where we find the agreement between our...

In recent data taking campaigns, the ALICE experiment recorded collisions of Xe-Xe as well as Pb-Pb ions at the unprecedented laboratory energies of $\sqrt{s_{NN}}=$ 5.44 and 5.02 TeV, respectively. This unique set of data allows to investigate bulk particle production for very different systems at similar multiplicities. In particular, the charged particle multiplicities in Xe-Xe collisions...

HADES provides a large acceptance combined with a high mass-resolution

and therefore allows to study dielectron and hadron production in

heavy-ion collisions with unprecedented precision. With the high

statistics of seven billion Au-Au collisions at 1.23 AGeV recorded in

2012 the investigation of collective effects and particle correlations

is possible with so far unprecedented accuracy.

At...

We present the latest developments in the ab-initio description of the initial state of heavy ion collisions at high energies and its coupling to relativistic viscous hydrodynamics. This includes the extension of the IP-Glasma model to include subnucleonic geometry fluctuations, shown to be present in electron-proton scattering, and the inclusion of the full energy-momentum tensor of the...

The NA61/SHINE experiment at the CERN SPS recently extended its program for the energy scan with Pb ions in the energy range of 13-150A GeV/c. Compared to the existing data from the NA49 experiment at the CERN SPS, the new data allows for more precise measurement of anisotropic flow harmonics. The fixed target setup of NA61/SHINE also allows to extend flow measurements available from the STAR...

Abstract:

I discuss how second and higher order cumulant momentum anisotropies may arise

in absence of all mechanisms generally expected to cause finite anisotropy harmonics $v_n$,

namely in absence of initial spatial asymmetries, in absence of initial density effects and in

absence of final state interactions. The mechanism is quantum and color interference of different

particle production...

We present the latest results from the event-by-event NLO pQCD + saturation + viscous hydrodynamics (EbyE NLO EKRT) model [1,2,3,4]. The parameters in the EKRT saturation model are fixed by the charged hadron multiplicity in the 0-5 \% 2.76 TeV Pb+Pb collisions, and the $\sqrt{s}$, A and centrality dependence of the initial particle production is determined by the QCD dynamics of the model....

Results on the production of stable light nuclei, including deuterons, $^{3}\rm{He}$, $^{4}\rm{He}$ and the corresponding anti-nuclei, in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV and $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be presented and compared with theoretical predictions to provide insight into the production mechanisms in heavy-ion collisions.

These information will be...