Phenomenology of Ultra-Relativistic Heavy-Ion Collisions

Abstract

PrefaceThe experimental studies of strongly interacting matter produced in ultrarelativistic heavy-ion collisions belong to the avant-garde of contemporary highenergy physics. This new and vastly developing field requires theoretical understanding how new experimental phenomena are related to the physical properties of the created system. This book delivers foundations of such understanding -it shows the links between basic theoretical concepts, discussed gradually from the elementary to more advanced level, and the results of experiments. In this way, I hope, experimentalists may learn more about the foundations of the models used by them to fit and interpret the data, while theoreticians may learn more about practical applications of their ideas.The book emphasizes the role played in the interpretation of the experimental results by thermodynamics, relativistic hydrodynamics, and relativistic kinetic theory. These frameworks are used to analyze the soft hadron production, i.e., the production of hadrons with relatively small transverse momenta with respect to the collision axis. Soft hadrons contribute to more than 90% of the produced particles and their measured properties reveal information about the bulk properties of the very hot and dense system formed at the early stages of collisions -an interacting quark-gluon plasma.A discussion of hard phenomena, i.e., the production of hadrons with large transverse momenta, has been omitted (except for the general comments concerning the jet quenching). Certainly, the role of hard processes is becoming more and more important with the increasing beam energy, however, their discussion would double the size of the present book.The successful application of the perfect-fluid hydrodynamics in description of ultra-relativistic heavy-ion collisions allows us to establish a uniform picture of these complicated processes. In some sense we are lucky that such complex systems may be described within a concise and well-defined framework. The perfect-fluid hydrodynamics, combined with the modeling of the initial state by the Glauber model or the color glass condensate on one side, and supplemented by the kinetic simulations of the freeze-out process on the other side, forms the foundation of an approach that may be regarded as the standard model of ultra-relativistic heavy-ion collisions. Yet, several shortcomings of the hydrodynamic approach indicate directions for many current and new investigations. To list a few: The problem of very early equilibration of matter formed in heavy-ion collisions is discussed in a very broad context including more elementary processes such as e + e − annihilation. Difficulties connected with the correct description of the correlations form a challenge for consistent modeling of the momentum and spacetime distributions of particles. Finally, the role of the viscosity and other dissipative effects should be elucidated. By the way, the recent developments in the field of dissipative hydrodynamics are examples of the permanent progress that is taki...

Thermodynamically Consistent Formulation of Quasiparticle Viscous Hydrodynamics

“…The resulting EoS of such a system depends only parametrically on the mass of the constituents (m = const.) [1]. Hence, within this approach it is impossible to reproduce a realistic EoS, such as the one obtained using lQCD calculations.…”

Modelling early stages of relativistic heavy-ion collisions

“…Due to lack of space we skip all the unnecessary details, referring to the original literature for a more complete treatment [1][2][3]. In the present study we limit ourselves to a simple geometrical initial condition with just one flux tube of a given transverse area.…”

Hagedorn’s Hadron Mass Spectrum and the Onset of Deconfinement

“…At freeze-out the system occupies a volume which is much larger than a volume of an individual hadron. Thus, one concludes that strongly interacting matter is created in heavy ion collisions [6].…”