Measurements of long-range correlations are one of the important tools for evaluation of the interplay between the initial- and final-state effects. Recently, non-vanishing second Fourier harmonic $\it{v}_{2}$ has been observed in small collision systems such as pp and p--Pb collisions. In this contribution, we present measurements of $\it{v}_{2}$ extracted from long-range two-particle...
We study fluctuations of particle number in the presence of critical point by utilizing molecular dynamics simulations of a classical Lennard-Jones fluid in a periodic box. The numerical solution of the $N$-body problem naturally incorporates all the relevant effects like physics of the correlation length, exact conservation laws, and finite size effects, allowing us to study the luctuation...
Two-particle correlations are a widely used tool for studying relativistic nuclear collisions. Multiplicity fluctuations have been studied as a possible signal for QGP and the QCD critical point. Momentum correlations and covariances of momentum fluctuations, which arise from the same correlation function, have also been used to extract properties of the nuclear collision medium such as the...
Measurements of two-particle correlations in $pp$ collisions show the presence of long-range correlations along $\Delta\eta$ that are strikingly similar to those seen in heavy-ion collisions.
In larger systems, the long-range correlations are known to arise from the collective dynamics of the produced quark-gluon plasma (QGP). The similarity between the $pp$ and heavy-ion measurements raises...
Because of the increasing gluon density towards small-$x$, a regime where these densities reach a saturation ($Q_{\rm sat}$) is expected. The observation of this gluon saturated matter has several consequences to particle production and is a matter of an entire effective field theory, the Color Glass Condensate. The Large Hadron Collider beauty (LHCb) experiment has a privileged geometry for...
The search for the Quantum Chromodynamics (QCD) critical point is underway at the Relativistic Heavy-Ion Collider (RHIC) Beam Energy Scan II. The primary signature of the critical point is a peak (divergence) in the kurtosis of the net-proton number distribution, $\kappa_4$. Most previous studies of kurtosis have focused on equilibrium physics, whereas it is well-known that out-of-equilibrium...
Near perfect fluid behavior is a hallmark signature of the quark gluon plasma (QGP), however, how this behavior emerges is still not fully understood. Thus, measurements of many different particles over a wide rapidity range are needed to understand this phenomenon. Heavy quark flow is expected to be different from light quark flow due to their larger masses, making heavy flavor flow...
Fluctuation observables in heavy-ion collisions probe the medium constituents, the chemical freeze-out and the transport properties of strongly interacting matter, and signal phase transitions. However, diffusion in the medium may blur some of the expected signals. It is thus crucial to understand the diffusive dynamics of the conserved charge fluctuations to know to which degree measured...
Modern models for describing heavy-ion collisions have difficulty reproducing observed flow in very central collisions -- a problem known as the ultra-central flow puzzle. It is therefore useful to understand what properties the initial stages must have in order to be compatible with experimental data. To this end, we parameterize the early-time energy density and its fluctuations via its...
A non-monotonic net-proton kurtosis for very central collisions at $\sqrt{s} = 200$ GeV has been suggested and may be confirmed by recent BES-II program results advocating the existence of the QCD critical point. Fluctuations at the origin of this peculiar behavior are produced in the highly dynamical environment of ultra-relativistic collisions. Especially, the violent longitudinal expansion...
The existence and location of the QCD critical point is an object of both experimental and theoretical studies. One of the main goals of NA61/SHINE, a fixed-target experiment at the CERN SPS, is the search for the critical point of the strongly interacting matter. The comprehensive data collected during a two-dimensional scan in beam momentum (13A-150A GeV/c) and system size (p+p, p+Pb, Be+Be,...
Nuclei with equal number of baryons but varying proton number (isobars) have many commonalities, but differ in both electric charge and nuclear structure. Relativistic collisions of such isobars provide unique opportunities to study the variation of the magnetic field, provided the nuclear structure is well understood. In this Letter we simulate collisions using several state-of-the-art...
Mini-jets, created by perturbative hard QCD collisions at moderate energies, can represent a significant portion of the total multiplicity of a heavy-ion collision event. Given the fact that their transverse momenta are initially larger than the typical saturation scale describing the bulk of the equilibrating QGP, they ought to be described through the physics of parton energy loss. Indeed,...
Two particle correlation analysis is often used to study the spatial and temporal extents of particle emitting source in high-energy nuclear collisions. By studying the quantum statistical effects (QS) and final state interactions (FSI) between two particles, one can extract emission source parameters used to describe the geometrical and dynamical properties of the homogeneity region....
Angular correlations of identified particles measured in ultrarelativistic proton-proton (pp) and heavy-ion collisions exhibit a number of features which depend on the collision system and particle type under consideration. Those features are produced by mechanisms, such as (mini)jets, elliptic flow, resonance decays, and conservation laws. In addition, of particular importance are those...
