This talk will address some of the fundamental questions, related to the applications of the Hanbury-Twiss effect in high energy physics: Is the two-particle HBT correlation function unity plus a positive definitene form – or not? Can it be described by two-particle symmetrization effects – or not? Is the shape of the correlation function a Gaussian – or not? The overview also includes some...
The RHIC beam energy scan program allows for the investigation of the phase diagram of QCD matter by varying the beam energy in the region where the change from crossover to first order phase transition is expected to occur. The nature of the quark-hadron transition can be studied through analyzing the space-time structure of the hadron emission source. One of the best tools to gain...
We present first results on identical pion intensity interferometry (HBT) studied in collisions of Au$(1.23A \mathrm{GeV})$+Au. The data are taken with the HADES spectrometer at SIS18/GSI Darmstadt. We study the dependence of the space-time extent of the pion emitting source on the pair transverse momentum and on the collision centrality. We compare our femtoscopic findings taken at an...
The dependence of BEC parameters on the jet structure of e+e- events (LEP) is discussed. The parametrization provided by the tau-model is used. This parametrization is also found to work well for pp minimum bias events (LHC). The BEC parameters of e+e- and pp events are compared.
Three different experimental techniques used in the measurements of two-particle, quantum-statistical (Bose-Einstein) femtoscopic correlations in proton-proton collisions at 13 TeV are introduced and discussed. Each one of them adopts a different analysis approach, with variable degrees of dependence on Monte Carlo event generator models. These are employed for estimating and correcting the...
The choice of the reference sample is a crucial component of the the Bose-Einstein correlations studies, with a great impact on the results obtained. Four reference samples are discussed. The unlike-sign pairs reference sample is affected by decay products of resonances. The momentum vector rotation of one track of the pair by an angle is found not to sufficiently remove correlations present...
We describe fireballs that rehadronize from a perfectly fluid quark matter to a chemically frozen, multi-component hadron gas. In the hydrodynamics of these fireballs, we utilize the lattice QCD equation of state, however, we also apply non-relativistic kinematics for simplicity and clarity. A realistic, linear mass scaling of the slope parameters of the single particle spectra of various...
Femtoscopy is a method used to investigate particle correlations by using the experimentally accessible two-particle momentum correlation function $C_k$. This function can be mathematically obtained by integrating the product of the source function and the two-particle wave function. The main goals of femtoscopy are to investigate the properties of the emission source and the interaction...
The recent results on the theoretical analysis of particle production and
correlation in relativistic heavy-ion collisions at the LHC and RHIC within
the hydrokinetic model (HKM) and its extended version — integrated hydrokinetic
model (iHKM) are addressed. The study of strange K meson spectrum and femtoscopy scales is discussed along with the pion ones for the case of LHC Pb+Pb collisions at...
Collisions of heavy-ions are major method used to study properties of matter. Such studies are performed with comparison of experimental data and model simulations.
One of theoretical description is Parton-Based Gribov-Regge theory included in the phenomenological model EPOS. It was originally created to explain the processes at the highest energies obtained with LHC complex. EPOS gives...
Forward-backward (FB) correlations are usually measured between observables obtained in an event-by-event analysis in two separated pseudorapidity intervals. Such correlations are considered to be a powerful tool for the exploration of the initial conditions of hadronic interactions. The conventional observable for the FB correlations analysis is the charged particle multiplicity. FB ...
Preliminary results for multiplicity and forward energy fluctuations are
presented for Be+Be and Ar+Sc collisions at 13A, 19A,
30A, 40A, 75A and 150A GeV/c beam momentum. The data were obtained by the
NA61/SHINE detector at the CERN SPS. Centrality selection and
forward energy measurement are based on the nucleon spectator energy
in the forward hemisphere determined by the Projectile...
The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. For these goals a scan of the two dimensional phase diagram (T-μB) is being performed at the SPS by measurements of hadron production in proton-nucleus and nucleus-nucleus interactions as a function of collision energy and system size.
In this...
One of the main motivations of heavy ion collision is to explore the QCD phase diagram of strong interaction. In the QCD phase diagram, at large $\mu_{B}$ the existence of critical point (CP) is expected. It is believed that, the non-monotonic behavior of higher moments of the distribution of conserved numbers with $\sqrt{s_{NN}}$ is a probe of the QCD critical point. The net-proton...
The modification in jets measured in heavy-ion collisions as compared to jets measured in pp collisions is a rich source of information on the medium properties. The medium-induced modifications are typically seen more clearly at low-$p_{\rm T}$, where full jet reconstruction is difficult due to the very large background in heavy ion collisions. Two-particle correlations provide a way to study...
I will discuss the physics of fluctuations near the QCD critical point and corresponding experimental signatures.
The transverse momentum ($p_{\rm T}$) spectra in proton-proton
collisions at $\sqrt{s}$ = 7 TeV, measured by the ALICE experiment at
the LHC are analyzed with a thermodynamically consistent Tsallis
distribution. The information about the freeze-out surface in terms of
freeze-out volume, temperature and the non-extensivity parameter, $q$,
for $K^{0}_{S}$, $\Lambda+\bar{\Lambda}$,...
Cumulants of conserved quantities are the powerful tools to study the QCD phase structure. According to the Lattice Gauge Theory calculation, at small $\mu_{B}$ a "smooth cross-over" for the transition from QGP to hadronic system occurs in heavy-ion collisions [1]. One of the possible ways to test the prediction is to measure the higher order cumulants of net-baryon or net-charge multiplicity...
Two-particle angular correlations are a robust tool which allow the explaration of the underlying physics phenomena of particle production in collisions of both protons and heavy ions by studying the distributions of angles in ∆η∆ϕ space (where ∆η is the pseudorapidity difference and ∆ϕ is the azimuthal angle difference between two particles). These correlations open up the possibility to...
Non-central heavy-ion collisions have large ($\sim 10^{3} \hbar$) angular momentum which may be transferred, in part, to the quark-gluon plasma through shear forces that generate a vortical substructure in the hydrodynamic flow field. The vortical nature of the system is expected to polarize emitted hadrons along the direction of system angular momentum. $\Lambda$ and $\overline{\Lambda}$...
In hydrodynamic approach to heavy ion collisions, hadrons with nonzero spin produced out of the fluid can acquire polarization via spin-vorticity thermodynamic coupling mechanism [1]. The hydrodynamical quantity steering the polarization is the thermal vorticity, that is minus the antisymmetric part of the gradient of four-temperature field $\beta^\mu=u^\mu/T$.
Based on this idea, it has been...
We study the correlation between the primordial electromagnetic (EM) fields
$\vec{E}$ and $\vec{B}$ and the initial matter geometry in p+Pb collisions.
The angular correlation between $\vec{B}$ and the second eccentricity harmonic
$\vec{\varepsilon}_2$ is substantially diminished in p+Pb compared to heavy ion
collisions (HICs), while those between $\vec{E}$ and the first eccentricity
harmonic...
In non-central heavy-ion collisions unprecedented strong magnetic fields are expected to be produced (O 1018 Gauss), whose interplay with quantum anomalies of the Quark-Gluon Plasma (QGP) has been predicted to lead to a number of interesting phenomena, such as the Chiral Magnetic Effect (CME). While several experimental observations are partially consistent with predictions of a CME signal, it...
Chiral Magnetic Effect (CME) is the macroscopic manifestation of the fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as anomalous transport current in the fluid dynamics framework. Experimental observation of CME is of great interest and has been reported in Dirac and Weyl semimetals. Significant efforts have also been made to search for CME in heavy ion...
In this talk, I will review the current status of theoretical studies of magnetic filed and associated observables in heavy-ion collisions. I will focus on the Chiral Magnetic Effect and discuss new ideas aiming at its unique identification. Specifically I will present the case for colliding nuclear isobars and report on
theoretical predictions and expectations.
In contrast to the traditional femtoscopic analysis of identical pions, measurements with kaons can serve as a cleaner probe as they are less affected by resonance decays. Kaons contain strange quarks and have smaller cross section with hadronic matter than pions, so they may be sensitive to different effects and/or earlier collision stages.
Moreover, non-identical kaon femtoscopy can...
Azimuthally differential femtoscopic measurements, being sensitive to spatiotemporal characteristics of the source as well as collective velocity fields at freeze-out, provide very important information on the nature and dynamics of
the system evolution. While the radii modulations with respect to the second
harmonic event plane reflect mostly the spatial geometry of the source, the
third...
Azimuthally differential HBT is a powerful tool for investigating the source shape at freeze out.
In heavy ion collisions, the medium expansion through radial and anisotropic flow has been observed.
These hydrodynamic expansions result the deformation of the initial geometry.
Studying the deformation of the source shape by such strong expansion is the key to quantify the dynamics of the system...
Femtoscopic correlations between K$^0_{\rm S}$ and K$^{\rm \pm}$ are studied for the first time. Unlike the case of identical-kaon pairs which have correlations from quantum statistics and, if charged, the Coulomb interaction, K$^0_{\rm S}$K$^{\rm \pm}$ correlations can only take place through a strong final-state interaction. Analyses were performed on data from Pb-Pb collisions at...
In high-energy heavy-ion collisions, a hot and dense strongly
interacting system of deconfined quarks and gluons (sQGP) is created.
The Beam Energy Scan program at RHIC was performed to map the QCD phase
diagram. Femtoscopy allows one to measure the space-time extent of the
particle emitting source created in heavy-ion collisions. In this talk,
we present preliminary results of the measurement...
Through experiments with heavy-ion collisions at high energies we can study the properties of nuclear matter under extreme conditions. The information on the sizes of the particle-emitting sources can be inferred via the method of femtoscopy.
The femtoscopy method uses Quantum Statistics effects and the Final State Interactions to determine the space-time properties of the source. The radii...
Lambda-Kaon Femtoscopy in Pb-Pb Collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with ALICE
We present results from a femtoscopic analysis of Lambda-Kaon correlations in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV by the ALICE experiment at the LHC. All pair combinations of $\Lambda$ and $\bar{\Lambda}$ with K$^{+}$, K$^{-}$ and K$^{0}_{S}$ are analyzed. The femtoscopic correlations are the...
THERMINATOR model is dedicated to heavy-ion collisions. Its current description allows one to work with data for the highest collision energies achieved by LHC and RHIC colliders. However it is possible to adapt THERMINATOR model to the lower energy spectrum as is used in Beam Energy Scan (BES) program at RHIC.
Femtoscopy of two particles investigates the properties of matter produced in...
The lifetimes of short-lived hadronic resonances are comparable to that of the hadronic phase which is present in the late stages of the evolution of heavy-ion collisions. Thus, these resonances are sensitive to the re-scattering and regeneration processes in the time interval between the chemical and kinetic freeze-out, which might affect the observed resonance yields. Recently, the...
The production of hadronic resonances such as K*(892)$^{0}$, $\phi$(1020), $\Sigma$(1385)$^{±}$, $\Lambda$(1520) and $\Xi(1530)^{0}$ has been measured as a function of multiplicity by the ALICE experiment in pp and p-Pb collisions at various energies at the LHC. These resonances differ by mass and strangeness content and thus can be used to provide insights on the mechanisms driving the...
The suppression of heavy quarkonia states in heavy-ion collisions is a phenomenon understood as a consequence of QGP
formation in the hot, dense system produced in interactions of heavy ions at high energy. In addition to hot matter
effects, cold nuclear effects can play an important role in quarkonia production. Therefore, a full assessment of
different physics scenarios requires detailed...
Given the relatively small hadronic interaction cross section, $\phi$ meson production provides a unique and complimentary method for exploring the hot and dense medium properties created in the relativistic heavy ion collisions. PHENIX measured $\phi$ production in a wide range of transverse momentum and rapidity in many collision systems. This talk will focus on the $\phi$ measurements at...
Femtoscopic correlations of two non-identical particles have a unique
feature, differentiating them from "traditional" identical particle
correlations, of being sensitive to the difference in average emission
position of the two particle types. For pion-kaon pairs the
femtoscopic signal arises from Coulomb interaction between particles.
Its strength is comparable to the magnitude of...
We study the particles emitted in the fireball following a Relativistic Heavy Ion Collision with the traditional angular analysis employed in cosmology and earth sciences, producing Mollweide plots of the p_t distribution of a few actual, publically released ALICE-collaboration events and calculating their angular power spectrum. With the limited statistics at hand, we do not find evidence for...
The strongly intensive observable involving multiplicities in two separated rapidity intervals (forward and backward) is analyzed in the model with particle production from the fragmentation of strings. In the case with independent identical strings the model calculation confirms that this observable does not depend on nor the number of string, nor its event-by-event fluctuation. The...
The pseudorapidity density of transverse energy per charged particle ($\frac{dE_T}{d\eta}/\frac{dN_{ch}}{d\eta} \equiv E_{T}/N_{ch}$) is an important
observable in high energy heavy-ion collisions, which reveals about the mechanism of particle production and the freeze-out criteria. Its collision energy and centrality dependence is exactly like the chemical freeze-out temperature till top RHIC...
The study of azimuthal anisotropy of particles produced in Heavy Ion collisions provides strong constrains to the evolution of the strongly coupled QCD medium and its event-by-event geometry fluctuations. The strength and predominance of these observables have long been identified as a manifestation of a strong collective behaviour in the formed medium.
However recent measurements of non-zero...
The formation of the QGP in heavy-ion collisions is well established by numerous measurements and their comparison to hydrodynamic models. This matter was not expected to be formed in smaller systems, such as p--Pb or pp collisions. However, in recent years, a growing number of results in small collision systems suggest that this hot and dense medium can be created in high multiplicity p--Pb...
Angular correlation measurements are powerful tools to study jets in a transverse momentum $(p_{\rm T})$ regime where jet reconstruction algorithms are difficult to use because of the large fluctuating background. In such measurements, the relative azimuthal angle $(\Delta\varphi)$ and relative pseudorapidity $(\Delta\eta)$ of particle pairs is measured. Jets manifest themselves as a peak...
Anisotropic flow is one of the key observables used to probe the properties and evolution of the hot and dense matter produced in heavy-ion collisions.
It was recently realized that event-by-event initial geometry fluctuations in heavy-ion collisions lead to a new type of correlation between different order anisotropic flow, which has unique sensitivity to initial conditions and shear...
The angular correlation function (CF) refers to the correlation of particles in the relative pseudorapidity and relative azimuthal angle. It is used to study strongly interacting matter properties at relativistic energies. Recent results from the ALICE experiment at LHC show unexpected structures of CF in the proton-proton and antiproton-antiproton correlations. Also results from the STAR...
Measurements of azimuthal anisotropic flow provide valuable information on the properties of the matter created in heavy-ion collisions. In this talk we present the elliptic, triangular and quadrangular flow of inclusive and identified charged particles measured in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV recorded by the ALICE detector. The measurements are presented for a wide...
We study the fluctuations and correlations of the average transverse momentum of particles emitted in heavy-ion collisions. The momentum fluctuations are related to event-by-event fluctuations of the size and entropy of the initial source. Hydrodynamic calculations using a Glauber model with quark degrees of freedom reproduce the data. We study correlation of the average transverse momentum in...
Event-by-event elliptic flow harmonic distributions $p(v_{2})$ are measured in PbPb collisions at $\sqrt{s_{NN}} = 5.02$~TeV using the CMS detector for the integrated $p_{T}$ range $0.3 < p_{T} < 3.0$~GeV/$c$ and pseudorapidity range $\left| eta \right|<1.0$. In order to gain insight on the nature of the initial geometry fluctuations, cumulant flow harmonics are calculated from the moments of...
The hot matter excited in ultrarelativistic heavy-ion collisions exhibits a sizeable
anisotropy in particle production. We formulate a generalisation of the blast-wave model which is suitable for description of higher
order azimuthal anisotropies in hadron production. The model includes anisotropy in density profile as
well as an anisotropy in the transverse expansion velocity field. These two...
The first phase of the RHIC Beam Energy Scan program (BES-I)
has revealed intriguing trends in observables as a function of
collision energy in the region $\sqrt{s_{NN}}\sim7-30$ GeV.
These include directed flow and global polarization measurements,
which require an accurate determination of the first-order event
plane. They also include measurement of higher-order moments of
the net-proton...
The main features of the femtoscopy measurements at top RHIC and LHC energies are considered as a manifestation of strong collective flow and are well interpreted within hydrodynamic models employing equation of
state (EoS) with a crossover type transition between Quark-Gluon Plasma (QGP) and hadron gas phases. The femtoscopy at lower energies was intensively studied at AGS and SPS...
By measuring event-by-event fluctuations over an ensemble of events via cumulants or moments of particle multiplicity distributions, one can study the freeze-out conditions in heavy-ion collisions and clarify their relation to the QCD phase transition. Higher order cumulants of fluctuations of conserved quantities like electric charge and baryon number are related to thermodynamic...
coming soon...
Limiting fragmentation (LF) or the longitudinal scaling is a well-studied phenomenon in multiparticle production processes observed at various heavy-ion collision experiments and in different types of colliding systems like- $e^+e^-$, $pp(\bar{p})$. It is interesting to verify the validity of this phenomenon at LHC energies. We study this phenomenon using the rapidity spectra of pions starting...
Search for Quark-Gluon Plasma (QGP) and characterization of the matter formed at high temperature and energy density are the major goals of studying ultra-relativistic heavy-ion collisions at RHIC and the LHC. The bulk properties of QGP are governed by the light quarks and the heavy quarks are important probes of QGP as they are produced during initial hard scattering and they witness the...
We propose event by event velocity fluctuations of nuclear fission fragments as an additional interesting observable that gives access to the nuclear temperature in an independent way from spectral measurements and relates the diffusion and friction coefficients for the relative fragment coordinate in Kramers-like models (in which some aspects of fission can be understood as the diffusion of a...
