Within the framework of the exploration of the nuclear matter phase diagram, the susceptibilities of conserved charges are useful tools to probe the existence of a 1st order phase transition, and a possible critical endpoint. They can be related to the cumulants of the considered net-charges, for which STAR collaboration recently published experimental measurements of proxies, in Au-Au...
We study fluctuations of particle number in the presence of a critical point by utilizing molecular dynamics simulations of the classical Lennard-Jones fluid in a periodic box. The numerical solution of the $N$-body problem naturally incorporates all correlations, exact conservation laws, and finite size effects, allowing us to study the fluctuation signatures of the critical point in a...
NA61/SHINE is a multipurpose fixed-target experiment at the CERN Super Proton Synchrotron. The main goals of the NA61/SHINE strong interactions program are to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. To reach these goals, hadron production measurements are performed in the form of a two-dimensional scan by varying...
The centrality dependence of the $p/\pi$ ratio measured by the ALICE Collaboration in 5.02 TeV Pb-Pb collisions indicates a statistically significant suppression with the increase of the charged multiplicity, once the centrality-correlated part of the systematic uncertainty is eliminated from the data. We argue that this behavior can be attributed to the presence of baryon annihilation in the...
Resonances of different lifetimes can be used to probe the hadronic stage of the fireball produced in relativistic heavy-ion collisions. For example, the $K^{*0}$ meson, with a lifetime of $\sim$ 4.16 fm/c, decays within the fireball and its decay daughters may experience in-medium effects like re-scattering and regeneration. On the other hand, the $\phi$ meson, having a long lifetime of...
The quantum chromodynamics (QCD) equation of state (EoS) at finite temperature
and density is of fundamental importance for the characterization of hot and
dense, strongly interacting matter created in heavy ion collision experiments.
It also has important applications in hydrodynamic simulations and
the EoS of the early universe.
Strongly interacting dense matter created in...
Using a (3+1)D hybrid hydrodynamic + hadronic transport framework with parametric initial conditions, we study the rapidity-dependent directed flow $v_1(y)$ of identified particles, including pions, kaons, protons, and lambdas, from 7.7 GeV to 200 GeV. The dynamics in the beam direction is first constrained using the measured pseudo-rapidity distribution of charged particles and the net...
The traditional Cooper-Frye freeze-out procedure becomes inadequate in heavy ion collisions that pass near a critical point, where fluctuations in the hydrodynamic densities (not just the mean densities) must be passed faithfully from the fluctuating fluid before freeze-out to the fluctuating particles after. Furthermore, the dynamics of the fluctuations must be computed, since because of...
There have been extensive studies to measure long-range correlations among produced particles from small collision systems, and the experimental results clearly indicate collective flow phenomena in these systems. Previously, PHENIX published elliptic and triangular flow results in high multiplicity $p$+Au, $d$+Au, and $^{3}$He+Au collisions. The results can be described by hydrodynamics...
STAR and PHENIX Collaborations have recently reported measurements of the anisotropic flow coefficients in p+Au, d+Au, and $^{3}$He+Au collisions at the Relativistic Heavy Ion Collider (RHIC). However, some tension between STAR and PHENIX data has not been fully resolved. Because the STAR and PHENIX Collaborations applied different pseudorapidity ranges to analyze the two-particle...
Directed and elliptic flow have been extensively studied in heavy-ion collisions while triangular flow ($v_3$) could be further explored. $v_3$ could prove very useful as a signal for Quark-Gluon Plasma (QGP) formation due to its sensitivity to QGP viscosity and the possibility that it is less affected by transport dynamics at very low energies [1]. In this talk, we will present the current...
The hydrodynamic modelling of heavy-ion collisions at energies from few to tens of GeV per NN pair brings new challenges as compared to simulations at top RHIC or LHC energies. The contraction of the incoming nuclei is much weaker resulting in a long inter-penetration phase and a more complex initial-state geometry. Conventional hydrodynamic models, where the fluid phase starts at a fixed...
We present the analytic description of particle number (conserved charge) fluctuations within the subvolume of the thermal system in the coexistence region of the first order phase transition. Different approximations are applied for the metastable states, for the region of spinodal decomposition [1] and in the special case of a homogeneous system [2]. The results are checked within...
Recently, a non-equilibrium effective field theory framework has been formulated for fluctuating hydrodynamics [1]. In this talk, we present an example of applying this novel formalism to study the critical properties of QCD. In the view that non-Gaussian fluctuations of baryon density are important for the QCD critical point search, we derive evolution equations for the critical non-Gaussian...
The existence and location of the QCD critical point is an object of both experimental and theoretical studies. The comprehensive data collected by the NA61/SHINE during a two-dimensional scan in beam momentum (13A-150A GeV/c) and system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb) allows for a systematic search for the critical point – a search for a non-monotonic dependence of...
In this work, we study the effects that different critical regions have on hydrodynamic trajectories both with and without viscous effects. Implementing the parametrized BEST collaboration equation of state [1,2], we find that the size and shape of the critical region is an important factor in determining whether the system will experience critical effects for a variety of initial conditions....
Predictions for the QCD equation of state across the phase diagram are made using Bayesian inference techniques within the holographic gauge/gravity correspondence. For that, we employ a Einstein-Maxwell-Dilaton (EMD) model capable of reproducing the latest lattice QCD results at zero and finite baryon density, known to predict a high-density critical endpoint. For the first time, we...
Functional forms of the neutron star Equation of State (EoS) are required to extract the viable EoS band from neutron star mergers. Typically, one of three methods are used-- spectral functions, piecewise polytropes, or gaussian process. However, realistic nuclear EoS, containing deconfined quarks or hyperons, present nontrivial features in the speed of sound such as bumps, kinks and plateaus....
Generating an ensemble of equations of state that fulfill multimessenger constraints, we statistically determine the properties of dense matter found inside neutron stars (NSs). We calculate the speed of sound and trace anomaly and demonstrate that they are driven towards their conformal values at the center of maximally massive NSs. The local peak of the speed of sound is shown to be located...
Diquark gap calculated within the framework of a micro-physical (non-local Nambu-Jona Lasinio) model coupled to color and electric neutrality constraints and fit to a μ-dependent ansatz, is employed to an algebraic quark EoS (equation of state) [1]. The effect of this μ-dependent diquark gap is investigated against that of a constant (diquark) gap in the same (algebraic) EoS.
Additional...
The structure factor ($\mathcal{S}_{nn}\,(k,\omega)$) of dynamical density fluctuation is studied in the presence of the out-of-equilibrium modes ($\phi$) within the scope of relativistic viscous hydrodynamics. The $\mathcal{S}_{nn}\,(k,\omega)$ without the $\phi$ modes shows three peaks of Lorentzian types, identified as one Rayleigh peak and two Brillouin peaks, symmetrically situated about...
In this talk we demonstrate that the early stages of the bottom-up thermalization scenario [1] are well described by the adiabatic hydrodynamization framework. All of the qualitative features exhibited in QCD effective kinetic theory (EKT) simulations at weak coupling [2] are captured by the emergence of an effective low-energy instantaneous ground state for the 1-particle gluon distribution...
Near the critical point in the QCD phase diagram, hydrodynamics breaks down at a momentum where the frequency of the fastest hydrodynamic mode becomes comparable with the decay rate of the slowest non-hydrodynamic mode. Hydro+ was developed as a framework which extends the range of validity of hydrodynamics beyond that momentum. In this talk, we first discuss the analytic structure of the...
Lattice simulations and functional approaches established that QCD has no phase transition at small baryon chemical potential. However, second order phase transitions are expected at the conjectured critical endpoint at larger chemical potential and in the chiral limit at vanishing chemical potential.
These phase transitions leave an imprint as Lee-Yang edge singularities and can be found...
QCD phase structure in the nonzero magnetic fields has attracted intensive interest recently as the strong magnetic field is expected to be present in the early stage of peripheral heavy-ion collisions, early universe and magnetars. In this talk we show that fluctuations of and correlations among net baryon number, strangeness and electrical charge can be useful to probe the imprint of the...
We study particle number fluctuations in infinite nuclear matter using hadronic transport simulations. We focus on matter initialized at a series of thermodynamically and mechanically stable points in the phase diagram, and in particular on the influence of the critical point on the equilibrated values of the fluctuations. We compare fluctuations from hadronic transport simulations against the...
