The single-and multi-particle inclusive spectra for strongly inhomogeneous thermal boson systems are studied using the method of statistical operator. The thermal Wick's theorem is generalized and the analytical solution of the problem for an boost-invariant expanding boson gas is found. The results demonstrate the effects of inhomogeneity for such a system: the spectra and correlations for particles with wave-lengths larger than the system's homogeneity lengths change essentially as compared with the results based on the local Bose-Einstein thermal distributions. The effects noticeable grow for overpopulated media, where the chemical potential associated with violation of chemical equilibrium is large enough.

After five years of running at RHIC, and on the eve of the LHC heavy-ion program, we highlight the status of femtoscopic measurements. We emphasize the role interferometry plays in addressing fundamental questions about the state of matter created in such collisions, and present an enumerated list of measurements, analyses and calculations that are needed to advance the field in the coming years.Keywords: Theoretical and experimental identical-particle correlations; Theoretical and experimental femtoscopy; Particleantiparticle correlationsThe first two-pion interferometric measurements of the collider era emerged within a year of RHIC becoming operational. To the surprise of many in the field, the measurements were remarkably similar to those recorded at the AGS and the SPS. The analyses were inconsistent, both qualitatively and quantitatively, with dynamic models incorporating first-order phase transitions in general. In fact, parametric explanations of the data, the forms of which are often motivated by solutions to dynamical equations, suggest that the matter explodes violently, growing from a radius of 6 fm to 13 fm in only 10 fm/c. The surprisingly strong acceleration required for such behavior and the associated failure of many of the field's most sophisticated models became known as the "HBT Puzzle".Five years later, the field has made steady progress on a variety of fronts. Theoretically, sophisticated dynamic models have more successfully reproduced experimental results (though the very sophistication of these models has made it difficult to ascertain which aspects of the models are being validated by the comparison). New techniques have been applied to the analysis of experimental correlation functions, revealing greater detail about the size and shape of the emission region. During our discussions at the workshop, it was clear that a remarkable consensus had developed among the practitioners of the field. Although this agreement by no means represented a final conclusion, we found numerous points that could be stated without dissent. In this white paper we will first list the points concerning the current status of the field, then further below, enumerate points where participants agreed were important for further progress. Achievements:• Remarkable agreement has been observed between the RHIC experiments, PHENIX, PHOBOS and STAR. All three have produced high-statistics high-quality pion correlations, whose apparent source sizes are consistent to a few tenths of a fm. A similar consistency was observed among measurements performed at the top SPS energy; at lower SPS energies the maximum deviations are on the level of 20%.• Femtoscopic studies are highly multi-dimensional. Even the simplest and most common case of twoidentical pion correlations depend on six independent variables, which have only been fully explored within the past few years. This includes extracting characteristic source sizes as function of transverse momentum, rapidity and the angle with respect to the reaction plane for off-axis co...

The paper is devoted to the theoretical study of particle production in the Large Hadron Collider (LHC) Xe+Xe collisions at the energy s N N = 5 . 44 TeV. The description of common bulk observables, such as mean charged particle multiplicity, particle number ratios, and p T spectra, is obtained within the integrated hydrokinetic model, and the simulation results are compared to the corresponding experimental points. The comparison shows that the model is able to adequately describe the measured data for the considered collision type, similarly as for the cases of Pb+Pb LHC collisions and top Relativistic Heavy Ion Collider (RHIC) energy Au+Au collisions, analyzed in our previous works.

The results on description of direct photon yields, transverse momentum spectra, and flow harmonics, measured in ultrarelativistic heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) for different collision centrality classes, analyzed within the Integrated Hydrokinetic Model (iHKM) are reviewed. The iHKM simulation results, corresponding to the two opposite approaches to the matter evolution treatment at the final stage of the system’s expansion within the model, namely, the chemically equilibrated and the chemically frozen evolution, are compared. The so-called “direct photon puzzle” is addressed, and its possible solution, suggesting the account for additional photon emission at confinement, is considered.