Short-range correlations of particles produced in relativistic heavy-ion collisions are actively studied both theoretically and experimentally, as the correlation functions provide information about space-time structure of the interactions zone. The correlations result from quantum statistics, when one deals with identical particles, and from final-state interactions of particles of interest....
I will briefly present the chiral mixing in hot and/or
dense matter and a potential impact over the dilepton
production rates.
We calculate total and differential cross sections
for $J/\psi$ photoproduction in ultrarelativistic lead-lead collisions
at the LHC energy $\sqrt{s_{NN}}=2.76$ TeV.
In the present approach we use a simple model based on vector dominance
picture and multiple scattering of the hadronic ($c \bar c$) state
in a cold nucleus as an example.
In our analysis we use both the classical mechanics and...
We performed state-of-the-art QCD effective kinetic theory simulations of chemically equilibrating QGP in longitudinally expanding systems. We find that chemical equilibration takes place after hydrodynamization, but well before local thermalization. By relating the transport properties of QGP and the system size we estimate that hadronic collisions with final state multiplicities dNch/dη≳10^2...
In a number of settings (including models of kinetic theory and strongly
coupled supersymmetric Yang-Mills theory), the pressure anisotropy of
boost-invariant flow is known to exhibit attractor behaviour well before local
equilibration is attained. I will describe some aspects of this phenomenon and
its possible implications for relativistic hydrodynamics.
So far light-by-light scattering ($\gamma\gamma \to \gamma\gamma$) was not accessible for experiments because the corresponding cross section is rather low. Measurements of diphotons in ultra-peripheral collisions (UPCs) of lead-lead have been reported recently by the ATLAS [1] and CMS Collaborations [2]. Our theoretical results based on equivalent photon approximation in the impact parameter...
"I am going present solutions of evolution equations for inclusive
distribution of gluons as produced by jet traversing quark-gluon
plasma. The the original equation is reformulated in such a form that
the virtual and unresolved-real emissions as well as unresolved
collisions with medium are resummed in a Sudakov-type form factor. The
resulting integral equations are then solved most...
The long-range azimuthal correlations in the nucleus-nucleus collisions are one of the signals of creation of the Quark-Gluon Plasma. At the LHC energies similar correlations are observed also in p+Pb and even pp collisions. After several years of successful operation of the Large Hadron Collider a wealth of data on pp, p+Pb and Pb+Pb collisions is available. This makes possible...
We discuss the energy and system size dependence of the charged-particle production at the LHC. The charged-particle multiplicity density (dN/deta), total charged-particle multiplicity (Ntot) and transverse momentum (pt) spectra are presented in the narrow centrality bins spanning 0-100% interval. The results are compared to phenomenological models and theoretical calculations based on...
Forward-backward (FB) multiplicity correlations carry important information on the early dynamics of ultra-relativistic heavy ion collisions. In this talk, new data on forward-backward charged particle correlations and multiplicity fluctuations in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 2.76$ TeV are presented. The data are recorded with the ALICE detector at the LHC. We focus on the...
The high-statistics experimental data collected by the ATLAS experiment during the 2015 Pb+Pb and 2017 Xe+Xe LHC runs are used to measure charged particle azimuthal anisotropy.
ATLAS measurements of differential and global Fourier harmonics of charged particles ($v_n$) in 5.02 TeV Pb+Pb and 5.44 TeV collisions in a wide range of transverse momenta (up to 60 GeV), pseudorapidity ($|\eta|$<2.5)...
One of the important results of the LHC Run 1 was the observation of an enhanced production of strange particles in high multiplicity pp and p-Pb collisions at 7 and 5.02 TeV, respectively. A smooth evolution of yields of strange particles relative to the non-strange ones with event multiplicity has been observed in such systems. Results from Run 2 at the top LHC energy are extended exploiting...
Our presentation will be based on our recent paper [1].
The centrality and energy dependence of rapidity distributions of pions in Pb+Pb reactions can be understood by imposing local energy-momentum conservation in the longitudinal “fire-streaks” of excited matter. With no tuning nor adjustment to the experimental data, the rapidity distribution of pions produced by the fire-streak which we...
Light-by-light (LbyL) scattering, $\gamma\gamma\rightarrow\gamma\gamma$, is a quantum-mechanical process, forbidden by the classical theory of electrodynamics, but possible in Quantum Electrodynamics via a loop diagram. Despite the small cross-section, it is theoretically possible to observe this process in ultra-peripheral high energy heavy-ion collisions. Based on 0.48 nb$^{-1}$ of 2015...
Using relativistic hydrodynamic equations for polarized spin 1/2 particles we determine the space-time evolution of the spin polarization in the system. In our approach, we use the forms of the energy-momentum and spin tensors based on de Groot, van Leeuwen, and van Weert. The calculations are done in a boost-invariant and transversely homogeneous setup. We present how the formalism of...
We consider a cluster expansion for strongly correlated quark matter where the clusters are baryons with spectral properties that are described within the generalized Beth-Uhlenbeck approach by a medium dependent phase shift. We employ a simple ansatz for the phase shift which fulfils the Levinson theorem by describing an on-shell bound state with an effective mass and models the continuum by...
NA61/SHINE is a multi-purpose experiment to study hadron-proton, hadron-nucleus and nucleus-nucleus collisions at the CERN Super Proton Synchrotron (SPS) with a large acceptance detector system. The measurements performed for a wide range of reactions provide valuable data for studying properties of hadronic matter under extreme conditions. They also provide precise results on hadron...
The search for experimental signatures of the critical point (CP) of strongly
interacting matter is one of the main objectives of the NA61/SHINE experiment
at CERN SPS. In the course of the experiment, an energy (beam momentum 13A
– 150A GeV/c) and system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La) scan is
performed.
We investigate local proton density fluctuations connected to the...
The study of hadron formation, interaction and their properties in hot and dense QCD matter is one of the main topics in sub-nuclear physics. The short-lived states ($\sim$1 fm/c), produced and decayed within the QCD matter contain fundamental information about the surrounding medium created in collisions of heavy-ions at relativistic energies as well as about the interaction. HADES measures...
Fluctuations of the net-proton number can be measured experimentally and
thus provide important information about the matter created during heavy
ion collisions. Especially, these quantities may give clues about the
conjectured QCD critical point. We discuss the beam-energy dependence of
ratios of first four cumulants of the net-proton number, obtained using
the phenomenologically motivated...
Recent lattice QCD studies at vanishing density exhibit the parity-doubling structure for the low-lying baryons around the chiral crossover temperature. This finding is likely an imprint of the chiral symmetry restoration in the baryonic sector of QCD, and is expected to occur also in cold dense matter, which makes it of major relevance for compact stars. By contrast, typical effective models...
The hard thermal (dense) loop (HTL) approach for the quark-gluon plasma
and the hadron resonance gas (nuclear statistical equilibrium) model for low-
density hadronic matter are well-studied limits of the equation of state for
strongly interacting matter. However, when investigating the transition
between both phases of QCD in heavy-ion collisions or in Astrophysics, the
question arises how...
Geometry and dynamics of the particle-emitting source in heavy-ion collisions at high energies can be inferred via femtoscopy method. Two-particle correlations at small relative momentum exploit Quantum Statistics and the Final State Interactions which allow one to study the space-time characteristics of the source of the order of 10−15 m and 10−23 s, respectively. The RHIC Beam Energy Scan...
We discuss the recently measured event-by-event multiplicity fluctuations in relativistic heavy-ion collisions. It is shown that the observed non-monotonic behaviour of the scaled variance of multiplicity distribution as a function of collision centrality (such effect is not observed in a widely used string-hadronic models of nuclear collisions) can be fully explained by the correlations...
It is known that the quark-gluon plasma is well described in terms of the perfect fluid dynamics. However, for a more realistic investigation, the dissipative processes quantified by the transport parameters need to be included in the hydrodynamic evolution of the QGP. We study the quark-flavor dependence of the shear viscosity calculated in the relaxation time approximation of the Boltzmann...
We investigate the forward backward multiplicity correlations for PbPb and pPb at the LHC energies. We examine various variants of Glauber models with sources interpreted as strings with fluctuating end points, as well as the effect of the fluctuations from particle production. Favorable comparisons to the data from the ATLAS and ALICE collaborations are achieved.
Two-particle angular correlations are a robust tool which allows the exploration 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...
Quantum-mechanical effects and interactions cause correlations between particles with small momentum difference that carry information about the space-time evolution of the collision system on the femtometer scale. Measurements of these effects are usually done soon after new data arrive and provide an unique input to theoretical models. Nowadays, after almost a decade of the LHC operation and...
Studying the properties of strongly interacting hot and dense medium created in heavy ion
collisions has been accomplished in part by studying the azimuthal anisotropy of particle emission
in the transverse plane, known as anisotropic flow. Flow measurements are key observable
because it reflects the viscous hydrodynamic response to the initial spatial anisotropy, produced
in the early stages...
One of the main goals of the NA61/SHINE experiment at the CERN SPS is to study properties of strongly interacting matter by a two-dimensional scan of elementary and nuclear reactions as a function of system size and collision energy. This talk presents new results on a new observable relevant for this part of the NA61/SHINE program, which is the modification of positively (negatively) charged...
