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The Hanbury-Brown and Twiss (HBT) effects predict a Bose–Einstein enhancement of the two-particle momentum correlations of identical bosons at small relative momentum. However, the parallel momentum correlations between identical fermions are less argued. The momentum correlations can be altered by many factors, among which the spin interaction effects are discussed in this paper. It is found that the spin interaction plays an important role on the momentum correlations of identical fermions. For spin triplet state, a full Fermi–Dirac suppression represents as expected. On the contrary, a fake Bose–Einstein enhancement shows up for spin singlet state. The measured momentum correlations of fermions could hence provide some hints of spin interactions between them if all other factors such as Coulomb interactions were removed. Spin interactions make it more complicated to extract physical information from momentum correlations between fermions.

Correlation functions measured in heavy-ion collisions are used to extract information about the space-time extent of the emitting sources. Similar techniques can be applied to study some spectroscopic properties of unbound states produced during the dynamical evolution of the colliding system.

The first year of LHC data taking provided an integrated luminosity of about 35 pb^-1 in proton–proton collisions at . The accelerator and the experiments have demonstrated an excellent performance. The experiments have obtained important physics results in many areas, ranging from tests of the Standard Model to searches for new particles. Among other results, the physics highlights have been the measurements of the W-, Z-boson and production cross-sections, improved limits on supersymmetric and other hypothetical particles and the observation of jet-quenching, elliptical flow and J/ψ suppression in lead–lead collisions at .

It is known that the presence of background magnetic field in cosmic plasma distorts the acoustic peaks in CMBR. This primarily results from different types of waves in the plasma with velocities depending on the angle between the magnetic field and the wave vector. We consider the consequences of these effects in relativistic heavy-ion collisions where very strong magnetic fields arise during early stages of the plasma evolution. We show that flow coefficients can be significantly affected by these effects when the magnetic field remains strong during early stages due to strong induced fields in the conducting plasma. In particular, the presence of magnetic field can lead to enhancement in the elliptic flow coefficient v₂.

We review up-to-date results on high-p_T particles and jets in heavy-ion collisions by three major LHC experiments, ALICE, ATLAS and CMS. Results of analyses of 2010 and 2011 Pb+Pb data at are discussed. We concentrate mainly on results by fully reconstructed jets and discuss similarities and important differences in measurements among experiments. We point to the importance of understanding the results in a view of difference between quark-initiated and gluon-initiated jets.

Rapid thermalization in ultra-relativistic heavy-ion collisions leads to fast changing potential between a heavy quark and antiquark from zero temperature potential to the finite temperature one. Time-dependent perturbation theory can then be used to calculate the survival probability of the initial quarkonium state. In view of very short time scales of thermalization at relativistic heavy-ion collider (RHIC) and large hadron collider (LHC) energies, we calculate the survival probability of $\mathrm{J∕\psi }$ and $\mathrm{\Upsilon }$ using sudden approximation. Our results show that quarkonium decay may be significant even when temperature of quark–gluon plasma (QGP) remains low enough so that the conventional quarkonium melting due to Debye screening is ineffective.

According to the usual application of the sequential-suppression picture to the dynamics of heavy quarkonia in the hot medium formed in ultrarelativistic nuclear collisions, quark–antiquark pairs created in a given bound or unbound state remain in that same state as the medium evolves. We argue that this scenario implicitly assumes an adiabatic evolution of the quarkonia and we show that the validity of the adiabaticity assumption is questionable.

In this work, we have extracted the initial temperature from the transverse momentum spectra of charged particles in Au + Au collisions using STAR data at RHIC energies from $\sqrt{s_{NN}}$ = 7.7–200 GeV. The initial energy density $(𝜀)$, shear viscosity to entropy density ratio $(\eta /s)$, trace anomaly $(\mathrm{\Delta })$, the squared speed of sound $(C_s^2)$, entropy density, and bulk viscosity to entropy density ratio $(\zeta /s)$ are obtained and compared with the lattice QCD calculations for (2 + 1) flavor. The initial temperatures obtained are compared with various hadronization and chemical freeze-out temperatures. The analysis of the data shows that the deconfinement-to-confinement transition possibly takes place between $\sqrt{s_{NN}}$ = 11.5 and 19.6 GeV.

We investigate the charged particle spectra produced in the heavy-ion collisions at nine centralities from different systems, i.e. $\mathrm{\text{Pb}}+\mathrm{\text{Pb}}$ at $\sqrt{s_{NN}}=2.76$ TeV and 5.02 TeV as well as $\mathrm{\text{Xe}}+\mathrm{\text{Xe}}$ at $\sqrt{s_{NN}}=5.44$ TeV, at Large Hadron Collider (LHC) using one empirical formula inspired by the stationary solution of the Fokker-Planck equation, dubbed as the generalized Fokker-Planck solution (GFPS). Our results show that the GFPS can reproduce the experimental particle spectrum up to transverse momentum $p_T$ about 45 GeV/c with the maximum discrepancy 30% covering 10 orders of magnitude. The discrepancy between the data and the results from the GFPS decreases to 15% when the maximum of the charged particle transverse momentum is cut to 20 GeV/c. We confirmed that the Tsallis distribution derived from the non-extensive statistics, which can reproduce the particle spectra produced in small collision systems, such as $\mathrm{\text{p}}+\mathrm{\text{p}}$, up to few hundreds GeV/c, can only apply to systematically study the particle spectra up to 8 GeV/c in $\mathrm{\text{A}}+\mathrm{\text{A}}$ collisions at LHC, as pointed out in the study of identified particle spectra in $\mathrm{\text{Pb}}+\mathrm{\text{Pb}}$ collisions at $\sqrt{s_{NN}}=2.76$ TeV. A brief discussion on GFPS is also given.

The experimental transverse momentum spectra of the charged pions and kaons, protons and antiprotons, produced at midrapidity in $p+p$ collisions at ${(s)}^{1/2}=2.76$ and 5.02 TeV, central (0–5%) and peripheral (60–80%) Pb+Pb collisions at ${(s_{nn})}^{1/2}=2.76$ TeV, central (0–5%), semicentral (40–50%) and peripheral (80–90%) Pb+Pb collisions at ${(s_{nn})}^{1/2}=5.02$ TeV, measured by ALICE collaboration, were analyzed using the Tsallis distribution function as well as Hagedorn formula with the embedded transverse flow. To exclude the influence (on the results) of different available fitting $p_t$ ranges in the analyzed collisions, we compare the results obtained from combined (simultaneous) fits of midrapidity spectra of the charged pions and kaons, protons and antiprotons with the above theoretical model functions using the identical fitting $p_t$ ranges in $p+p$ as well as Pb+Pb collisions at ${(s_{nn})}^{1/2}=2.76$ and 5.02 TeV. Using the combined fits with the thermodynamically consistent Tsallis distribution as well as the simple Tsallis distribution without thermodynamical description, it is obtained that the global temperature $T$ and non-extensivity parameter $q$ slightly increase (consistently for all the particle types) with an increase in center-of-mass (c.m.) energy ${(s)}^{1/2}$ of $p+p$ collisions from 2.76 TeV to 5.02 TeV, indicating that the more violent and faster $p+p$ collisions at ${(s)}^{1/2}=5.02$ TeV result in a smaller degree of thermalization (higher degree of non-equilibrium) compared to that in $p+p$ collisions at ${(s)}^{1/2}=2.76$ TeV. The $q$ values for pions and kaons proved to be very close to each other, whereas $q$ for protons and antiprotons proved to be significantly lower than that for pions and kaons, that is $q(\mathrm{\text{baryons}})<q(\mathrm{\text{mesons}})$. The results of the combined fits using Hagedorn formula with the embedded transverse flow are consistent with practically no (zero) transverse (radial) flow in $p+p$ collisions at ${(s)}^{1/2}=2.76$ and 5.02 TeV. Using Hagedorn formula with the embedded transverse flow, it is obtained that the value of the (average) transverse flow velocity increases and the temperature $T$ decreases with an increase in collision centrality in Pb+Pb collisions at ${(s_{nn})}^{1/2}=2.76$ and 5.02 TeV, which is in good agreement with the results of the combined Boltzmann–Gibbs blast-wave fits to the particle spectra in Pb+Pb collisions at ${(s_{nn})}^{1/2}=2.76$ and 5.02 TeV in recent works of ALICE collaboration. The temperature $(T)$ parameter, which approximates the kinetic freeze-out temperature, was shown to coincide in central (0–5%) Pb+Pb collisions at ${(s_{nn})}^{1/2}=2.76$ and 5.02 TeV, which implies, taking into account the results of our previous analysis, that kinetic freeze-out temperature stays practically constant in central heavy-ion collisions in ${(s_{nn})}^{1/2}=200\text{–}5020$ GeV energy range.

The extremely large electromagnetic fields generated in heavy-ion collisions provide access to novel observables that are expected to constrain various key transport properties of the quark-gluon plasma and could help solve one of the outstanding puzzles in QCD: the strong CP problem. In this review we present a brief overview of the theoretical and experimental characterization of these electromagnetic fields. After reviewing the current state, emphasizing one of the observables — the charge-dependent flow — we discuss the various discrepancies between the measurements and theoretical predictions. Finally, to help resolve the discrepancies, we suggest new measurements and theoretical ideas.

In this paper, a search for power-law fluctuations with fractality and intermittency analysis to explore the QCD phase diagram and the critical point is summarized. Experimental data on self-similar correlations and fluctuations with respect to the size of phase–space volume in various high energy heavy-ion collisions are presented, with special emphasis on background subtraction and efficiency correction of the measurement. Phenomenological modeling and theoretical work on the subject are discussed. Finally, we highlight possible directions for future research.

Various heavy quarkonium states can be employed as a testing ground for the magnetic field created and later possibly persisted in heavy ion collision (HIC) experiments. In this paper, we have shown the modification in the binding energies, and ionization potentials categorically for different species of quarkonia in the medium in the presence of a magnetic field. For the study, we have considered quarkonium states which are well described by the real-valued effective potential in the thermal medium which is evolving by respecting the hydrodynamical power law. Furthermore while addressing the issue of their survival, we have not ignored the possibility of transitions between various bound-to-bound and bound-to-unbound states for different charmonium and bottomonium states. Our analysis shows that this phenomenon can be considered as a benchmark for understanding the presence, strength and persistence of the magnetic field which is expected to be produced through the high-energy nucleus–nucleus collisions.

The lepton charge asymmetry in $W^{\pm }$ production in the nuclear collisions at $\sqrt{s_{\mathrm{\text{NN}}}}=5.02$TeV is investigated with a parton and hadron cascade model PACIAE. Recently published ALICE and the ATLAS data of lepton charge asymmetry are well reproduced. An interesting linear scaling behavior is observed in the lepton charge asymmetry as a function of the collision system valence quark number asymmetry among different sizes of nuclear collision systems at $\sqrt{s_{\mathrm{\text{NN}}}}=5.02$TeV. This linear scaling behavior may serve as an additional constraint on the PDF (nPDF) extractions.

The experimental observation of disoriented chiral condensate is affected due to various physical and detector related effects. We study and quantify the strength of the experimental signal, "neutral pion fraction" within the framework of a simple DCC model, using the analysis methods based on the multi-resolution discrete wavelet technique and by evaluating the signal to background ratio. The scope and limitations of DCC search in heavy-ion collision experiments using various combination of detector systems are investigated.

Nuclear matter is predicted to undergo a phase transition and become a plasma of quarks and gluons (QGP) at high temperature and density. Recent experimental results from high-energy heavy-ion collisions at the Relativistic Heavy-ion Collider (RHIC) indicate the production of a strongly interacting quark-gluon matter with fluid-like properties. I will discuss some expected features of QCD at high temperature and density, theoretical interpretations of experimental observations and challenges in unraveling some of the basic properties of dense matter in the strongly interacting regime.

Magnetic fields created in the noncentral heavy-ion collision are studied within a microscopic transport model, namely the Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). Simulations were carried out for different impact parameters within the SPS energy range (E_lab = 10-158A GeV) and for highest energies accessible for RHIC. We show that the magnetic field emerging in heavy-ion collisions has the magnitude of the order of for the SPS energy range and for the RHIC energies. The estimated value of the magnetic field strength for the LHC energy amounts to .

A novel attempt has been made to probe the QCD phase boundary by using the experimental data for transverse momenta of ϕ mesons produced in nuclear collisions at AGS, SPS and RHIC energies. The data are confronted with simple thermodynamic expectations and lattice QCD results. The experimental data indicate a first-order phase transition, with a mixed phase stretching the energy density between ~1 and 3.2 GeV/fm³ corresponding to SPS energies.

We review progress in the hydrodynamic description of heavy-ion collisions, focusing on recent developments in modeling the fluctuating initial state and event-by-event viscous hydrodynamic simulations. We discuss how hydrodynamics can be used to extract information on fundamental properties of quantum chromodynamics from experimental data, and review successes and challenges of the hydrodynamic framework.

Jets are expected to play a prominent role in the ongoing efforts to characterize the hot and dense QCD medium created in ultrarelativistic heavy-ion collisions. The success of this program depends crucially on the existence of a full theoretical account of the dynamical effects of the medium on the jets that develop within it. By focussing on the discussion of the essential ingredients underlying such a theoretical formulation, we aim to set the appropriate context in which current and future developments can be understood.