Proceedings Series


Vol. 3 (2010), No. 3, pp. 495 – 776

EMMI Workshop and XXVI Max Born Symposium Three Days of Strong Interactions

Wrocław, Poland; July 9-11, 2009

Science, Scientists and Show


Why Do We Speak of Laws of Nature?

abstract

The concept of a law of nature has origins which date back several millennia. The idea of a divine law-giver is found in the Mesopotamian, Jewish and Christian religions. Hellenistic scientists did not speak of laws, but used mathematical terms to describe their discoveries. The religious and scientific traditions would not converge, however, until Descartes and Newton laid the foundations of modern science and shaped the modern concept of a law of nature. It seems that during the 20th century this notion gradually comes out of use at least in the scientific language.


Fluctuations in Relativistic Heavy-ion Collisions from the Glauber Models

abstract

In the first part of the paper we discuss the role of the two-body nucleon–nucleon correlations on signatures of the heavy-ion collisions which are a priori expected to be sensitive to these effects. We find that while the fluctuations of the number of produced particles are indeed affected, other quantities (\(v_2\) fluctuations, size fluctuations) are insensitive to the presence of the \(NN\) correlations in the nucleon distributions. In the second part we show that the fluctuations of the transverse size of the initial source cause, after a suitable hydrodynamic evolution, fluctuations of the transverse flow velocity at hadronic freeze-out. This in turn yields the event-by-event fluctuations of the transverse momentum of the produced particles, \(\langle p_{\rm T} \rangle \). Our results demonstrate that practically all of the observed event-by-event \(\langle p_{\rm T} \rangle \) fluctuations may be explained this way.


Inhomogeneous Phases of Strongly Interacting Matter

abstract

We discuss possible inhomogeneous phases in two regions of the QCD phase diagram: We begin with color superconducting quark matter at moderately high densities, which is an imbalanced Fermi system due to the finite strange quark mass and neutrality constraints. Within an NJL-type toy model we find that this situation could lead to the formation of a soliton lattice. Similar solutions also exist in the context of the chiral phase transition. As an interesting result, the first-order transition line in the phase diagram of homogeneous phases gets replaced by an inhomogeneous phase which is bordered by two second-order transition lines.


Strangeness Excitation Functions and Transition from Baryonic to Mesonic Freeze-out

abstract

The sharp peak in the \(K^+/\pi ^+\) ratio in relativistic heavy-ion collisions is discussed in the framework of the Statistical Model. In this model a rapid change is expected as the hadronic gas undergoes a transition from a baryon-dominated to a meson-dominated gas. The maximum in the \({\mit \Lambda }/\pi \) ratio is well reproduced by the Statistical Model, but the change in the \(K^+/\pi ^+\) ratio is somewhat less pronounced than the one observed by the NA49 Collaboration. The calculated smooth increase of the \(K^-/\pi ^-\) ratio and the shape of the \({\mit \Xi }^-/\pi ^+\) and \({\mit \Omega }^-/\pi ^+\) ratios exhibiting maxima at different incident energies is consistent with the presently available experimental data. We conclude that the measured particle ratios with 20–30% deviations agree with a hadronic freeze-out scenario. These deviations seem to occur just in the transition from baryon-dominated to meson-dominated freeze-out.


The Casimir Effect

abstract

The Casimir effect is usually interpreted as due to the modification of the zero point energy of QED when two perfectly conducting plates are put very close to each other, and as a proof of the “reality” of this zero point energy. The Dark Energy, necessary to explain the acceleration of the expansion of the Universe is sometimes viewed as another proof of the same reality. The usual interpretation of the Casimir effect is however challenged by some authors who rather consider it as a “giant” van der Waals effect. All these aspects are shortly reviewed.


Dual Order Parameters and the Deconfinement Transition

abstract

We investigate the chiral and the deconfinement transition within the framework of Dyson–Schwinger equations using quenched lattice data for the temperature dependent gluon propagator as input. We extract corresponding order parameters from the Landau gauge quark propagator with U(1)-valued boundary conditions. We study the chiral transition using the conventional quark condensate, whereas for the deconfinement transition we determine the dual condensate (‘dressed Polyakov loop’). In addition, we consider an alternative order parameter for deconfinement, the dual scalar quark dressing function. As a result we find almost the same transition temperatures for the chiral and deconfinement transitions.


Transverse Hydrodynamics with Sudden Isotropization and Freeze-out

abstract

We assume that the early evolution of matter produced in relativistic heavy-ion collisions is described by the transverse hydrodynamics. In this approach only transverse degrees of freedom are thermalized, while the longitudinal motion is described by free streaming. When the energy density of the system drops to a certain value, the system becomes isotropic (locally, in the momentum space) and freezes out. The sudden isotropization transition is described with the help of the Landau matching conditions, and the freeze-out is modeled with Therminator. Within this scenario one is able to reproduce in the quite satisfactory way the transverse-momentum spectra, the elliptic flow coefficient \(v_2\), and the HBT radii of pions studied at RHIC (Au + Au collisions at \(\sqrt {s_{NN}} = 200 \) GeV). The obtained results indicate that the system produced at RHIC does not have to be fully thermalized in the early stage. On the other hand, the final three-dimensional thermalization is necessary to reproduce the HBT radius \(R_{\rm long}\).


QCD Thermodynamics and the Polyakov Loop

abstract

We discuss the phase diagram of QCD at finite temperature \(T\) and baryon chemical potential \(\mu _B\) using the Polyakov-loop coupled Nambu–Jona-Lasinio (PNJL) model. We propose a way to prescribe the phase diagram by means of the thermodynamic quantities. We find that the resulting phase diagram is consistent with the conventional one defined by the chiral condensate and the Polyakov loop.


AdS/CFT and Heavy Ion Collisions

abstract

I describe the parton picture at strong coupling as emerging from the gauge/gravity duality and its consequences for high-energy scattering and for the hard probes of a strongly coupled plasma, as potentially relevant for heavy collisions at RHIC and LHC. I emphasize the differences with respect to the corresponding picture in perturbative QCD.


Non-congruent Phase Transitions in Cosmic Matter and in the Laboratory

abstract

Non-congruence appears to be the most general form of phase transition in cosmic matter and in the laboratory. In terrestrial applications non-congruence means coexistence of phases with different chemical composition in systems consisting of two (or more) chemical elements. It is just the case for all phase transitions in high-temperature chemically reactive mixtures, which are typical for uranium-bearing compounds in many nuclear energy devices, both contemporary and perspective. As for cosmic matter, most of real and hypothetical phase transitions without nuclear reactions, i.e. , those in the interiors of giant planets (solar and extrasolar), those in brown dwarfs and other sub-stellar objects, as well as in the outer crust of compact stars, are very plausible candidates for such type of phase transformations. Two exotic phase transitions, the gas–liquid phase transition in dense nuclear matter and the quark–hadron transition occurring in the interior of compact stars as well as in high-energy heavy-ion collisions are under discussion as the most extreme example of hypothetical non-congruence for phase transformations in High Energy Density Matter.


all authors

C.M. Ko, S.H. Lee, W. Liu, Y. Oh, S. Yasui, B.-W. Zhang

Charms in Relativistic Heavy-ion Collisions

abstract

Studying charm production in relativistic heavy-ion collisions provides the possibility to probe the properties of produced quark–gluon plasma. In this paper, we review our work on charm quark energy loss, charmed baryon to meson ratio, thermal charm production, and the production of charmed multiquark hadrons in relativistic heavy-ion collisions.


The Equation of State From Lattice QCD

abstract

Numerical results on the QCD equation-of-state from lattices with temporal extents 4, 6 and 8 are presented. The computations have been performed within two different discretization schemes, the p4 and the asqtad actions which improve lattice artefacts for thermodynamic observables at high temperatures. In the course of these computations also observables that are sensitive to deconfinement and chiral symmetry restoration were analyzed. In addition, quantities measuring fluctuations and correlations of baryon number, strangeness and electric charge have been studied.


Dissipative Superfluids, from Cold Atoms to Quark Matter

abstract

Some results about dissipative processes in superfluids are presented. We focus on fermionic superfluidity and restrict our analysis to the contribution of phonons to bulk viscosity, shear viscosity and thermal conductivity. At sufficiently low temperatures phonons give the dominant contribution to the transport coefficients if all the other low energy excitations of the system are gapped. We first consider a system of cold fermionic atoms close to the unitarity limit. Then we turn to the superfluid phase of quark matter that may be realized at high baryonic density.


New View of the QCD Phase Diagram

abstract

Quarkyonic matter is confining but can have densities much larger than \({\mit \Lambda }_{\rm QCD}^3\). Its existence is argued in the large \(N_c\) limit of QCD and implies that there are at least three phases of QCD with greatly different bulk properties. These are a Confined Phase of hadrons, a Deconfined Phase of quarks and gluons, and the Quarkyonic Phase. In the Quarkyonic Phase, the baryon density is accounted for by a quasi-free gas of quarks, and the antiquarks and gluons are confined into mesons, glueballs. Quarks near the Fermi surface also are treated as baryons. (In addition to these phases, there is a color superconducting phase that has vastly different transport properties than the above, but with bulk properties, such as pressure and energy density, that are not greatly different than that of Quarkyonic Matter.)


On the Dynamics of Unstable Quark-Gluon Plasma

abstract

Since the quark-gluon plasma, which is unstable due to anisotropic momentum distribution, evolves fast in time, plasma’s characteristics have to be studied as initial value problems. The chromodynamic fluctuations and the momentum broadening of a fast parton traversing the plasma are discussed here. The two quantities are shown to exponentially grow in time.


Medium Effects and Quantum Condensates in Low-density Nuclear Matter

abstract

The equation of state of nuclear matter at finite temperature and density with various proton fractions is considered at subsaturation densities and finite temperatures. The formation of few-body correlations, in particular bound clusters is taken into account considering free nucleons, as well as clusters, like quasiparticles. Medium modification of the clusters is described by self-energy and Pauli blocking effects. Benchmarks such as the nuclear statistical equilibrium, virial expansion and the relativistic mean field approximation are considered. An interesting effect is the formation of a two-nucleon or four-particle quantum condensate, showing the crossover from Cooper pairing to Bose–Einstein condensation. The resulting thermodynamic properties are of interest for heavy-ion collisions and astrophysical applications. Quantum condensates and the Mott effect are also of relevance for the structure of finite nuclei, especially dilute excited states like the Hoyle state of \(^{12}\)C.


The Phase Structure of Dense QCD from Chiral Models

abstract

A new phase of dense QCD proposed in the limit of large number of colors, Quarkyonic Phase, is discussed in chiral approaches. The interplay between chiral symmetry breaking and confinement together with the \(N_c\) dependence of the phase diagram are dealt with in the PNJL model. We also discuss a possible phase at finite density where chiral symmetry is spontaneously broken while its center remains unbroken. The quark number susceptibility exhibits a strong enhancement at the restoration point of the center symmetry rather than that of the chiral symmetry. This is reminiscent of the quarkyonic transition.


Astrophysics of Dense Quark Matter in Compact Stars

abstract

Massive neutron stars may harbor deconfined quark matter in their cores. I review some recent work on the microphysics and the phenomenology of compact stars with cores made of quark matter. This includes the equilibrium and stability of non-rotating and rapidly rotating stars, gravitational radiation from deformations in their quark cores, neutrino radiation and dichotomy of fast and slow cooling, and pulsar radio-timing anomalies.


Low-mass Dileptons in Heavy-ion Collisions

abstract

A review of low-mass dilepton production in heavy-ion collisions is presented, covering measurements performed over a very broad energy range from 1–2 \(A\)GeV at the BEVALAC or GSI, to 40–200 \(A\)GeV at the SPS and up to \(\sqrt {s_{_{NN}}}=200\) GeV at RHIC.


QCD Thermodynamics: Confronting the Polyakov-Quark–Meson Model with Lattice QCD

abstract

NJL-type effective models represent a low-energy realization of QCD and incorporate pertinent aspects such as chiral symmetry and its spontaneous breaking, the center symmetry in the heavy-quark limit as well as the axial anomaly. One such model, the Polyakov-quark–meson model for three light quark flavors, is introduced in order to study the phase structure of strongly-interacting matter. With recent high-statistics lattice QCD simulations of the finite-temperature equation of state, a detailed comparison with model results becomes accessible. Such comparisons allow to estimate volume and truncation effects of quantities, obtained on the lattice and provide possible lattice extrapolation procedures to finite chemical potential which are important to locate a critical endpoint in the QCD phase diagram.


Phase Transitions in Dense Baryonic Matter and Cooling of Rotating Neutron Stars

abstract

New astrophysical instruments such as skA (square kilometer Array) and IXO (formerly Constellation X) promise the discovery of tens of thousands of new isolated rotating neutron stars (pulsars), neutron stars in low-mass X-ray binaries (LMXBs), anomalous X-ray pulsars (AXPs), and soft gamma repeaters (SGRs). Many of these neutron stars will experience dramatic density changes over their active lifetimes, driven by either stellar spin-up or spin-down, which may trigger phase transitions in their dense baryonic cores. More than that, accretion of matter onto neutron stars in LMXBs is believed to cause pycno-nuclear fusion reactions in the inner crusts of neutron stars. The associated reaction rates may be drastically altered if strange quark matter would be absolutely stable. This paper outlines the investigative steps that need to be performed in order to explore the thermal response of neutron stars to rotationally-driven phase transitions in their cores as well as to nuclear burning scenarios in their crusts. Such research complements the exploration of the phase diagram of dense baryonic matter through particle collider experiments, as performed at RHIC in the USA and as planned at the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany.


Charmonium Production at the LHC

abstract

We summarise the perspectives on quarkonium, in particular charmonium, detection at the LHC, both for proton–proton and heavy-ion collisions. We give a review of the experimental capabilities of the four LHC detectors: ALICE, ATLAS, CMS and LHCb.


Lowest Negative Parity Baryons in the \(1/N_c\) Expansion

abstract

We review a recently proposed approach to study the lowest negative parity baryons within the \(1/N_c\) expansion. The method is based on the derivation of the matrix elements of SU(\(2N_f\)) generators for mixed symmetric \([N_c-1,1]\) flavor-spin states. Presently it is applied to the \(N = 1\) band and a comparison is made with a former method based on the decoupling of the system into a symmetric core of \(N_c-1\) quarks and an excited one. We prove that the decoupling is not necessary and moreover, it misses some important physical consequences.


QED Thermodynamics at Intermediate Coupling

abstract

We discuss reorganizing finite temperature perturbation theory using hard-thermal-loop (HTL) perturbation theory in order to improve the convergence of successive perturbative approximations to the free energy of a gauge theory. We briefly review the history of the technique and present new results for the three-loop HTL-improved approximation for the free energy of QED. We show that the hard-thermal-loop perturbation reorganization improves the convergence of the successive approximations to the QED free energy at intermediate coupling, \(e \sim 2\). The reorganization is gauge invariant by construction, and due to cancellation among various contributions, one can obtain a completely analytic result for the resummed thermodynamic potential at three loops.


A Microscopic Study of Pion Condensation Within Nambu–Jona-Lasinio Model

abstract

We have studied the phenomenology of pion condensation in 2-flavor neutral quark matter at finite density with Nambu–Jona-Lasinio (NJL) model of QCD. We have discussed the role of the bare quark mass \(m\) and the electric chemical potential \(\mu _{e}\) in controlling the condensation. The central result of this work is that the onset for \(\pi \)-condensed phase occurs when \(|\mu _{e}|\) reaches the value of the in-medium pion mass \(M_{\pi }\), provided the transition is of the second order, even for a composite pion system in the medium. Finally, we have shown that the condensation is extremely fragile with respect to the explicit chiral symmetry breaking via a finite current quark mass.


Accessibility of Color Superconducting Quark Matter Phases in Heavy-ion Collisions

abstract

We discuss a hybrid equation of state (EoS) that fulfills constraints for mass-radius relationships and cooling of compact stars. The quark matter EoS is obtained from a Polyakov-loop Nambu–Jona-Lasinio (PNJL) model with color superconductivity, and the hadronic one from a relativistic mean-field (RMF) model with density-dependent couplings (DD–RMF). For the construction of the phase transition regions we employ here for simplicity a Maxwell construction. We present the phase diagram for symmetric matter which exhibits two remarkable features: (1) a “nose”-like structure of the hadronic-to-quark matter phase border with an increase of the critical density at temperatures below \(T \sim 150\) MeV and (2) a high critical temperature for the border of the two-flavor color superconducting (2SC) phase, \(T_{\rm c} \gt 160\) MeV. We show the trajectories of heavy-ion collisions in the plane of excitation energy versus baryon density calculated using the UrQMD code and conjecture that for incident energies of \(4 \dots 8\) \(A\) GeV as provided, e.g., by the Nuclotron-M at JINR Dubna or by lowest energies at the future heavy-ion collision experiments CBM at FAIR and NICA at JINR, the color superconducting quark matter phase becomes accessible.


Quarkonium Dissociation in a Polyakov–Nambu–Jona-Lasinio Quark Plasma

abstract

We investigate the Mott effect for heavy quarkonia due to Debye screening of the heavy quark potential in a plasma of massless quarks and antiquarks. The influence of residual color correlation is investigated by coupling the light quark sector to a temporal gauge field driven by the Polyakov loop potential. This leads to an increase of the Mott dissociation temperatures for quarkonia states which stabilizes in particular the excited states, but has marginal effect on the ground states. The temperature dependence of binding energies suggests that the dissciation of the charmonium (bottomonium) ground state by thermal activation sets in at temperatures of 200 MeV (250 MeV).


EoS and Bulk Viscosity of Cold Quark Matter in a Running Coupling NJL Model

abstract

We analyze the thermodynamical properties of color superconducting quark matter in the isotropic color spin locking (iso-CSL) phase at zero temperature and finite chemical potential. We perform calculations in the NJL model with quark–quark and quark–antiquark coupling for two parametrizations of the coupling strength: (a) constant value and (b) logarithmic dependence on the chemical potential. The bulk viscosity of the iso-CSL phase is calculated for both parametrizations for electrically neutral two-flavor matter in \(\beta \)-equilibrium. We discuss an extension of this model to the three-flavor case where we find that behaviour of the strange quark mass is qualitatively different for the cases (a) and (b). In this context we examine the influence of the value of QCD momentum scale \({\mit \Lambda }_{\rm {QCD}}\) and investigate the stability of three-flavor quark matter in the iso-CSL phase under compact star (CS) constraints.


Decay Widths of Charmonia in a Hot Equilibrated Medium

abstract

We investigate the properties of charmonia in a thermal medium, showing that with increasing temperature the decay widths of these mesons behave in a non-trivial way. Employing a potential model with interaction potential extracted from thermal lattice QCD calculations of the free-energy of a static quark–antiquark pair, we study some decay processes in the crossover region. We find that at temperatures \(T \sim T_{\rm c}\) the decay widths of the \(J/{\mit \Psi }\) that depend on the value of the wave function at the origin are enhanced with respect to the values in vacuum. In the same temperature range the decay width of the process \(\chi _{cJ} \to J/{\mit \Psi } + \gamma \) is enhanced by approximately a factor \(6\) with respect to the value in vacuum. At higher temperatures the charmonia states dissociate and the widths of both decay processes become vanishing small.


MARTINI — Monte Carlo Simulation of Jet Evolution

abstract

We present the Modular Algorithm for Relativistic Treatment of heavy IoN Interactions (MARTINI), an event generator for the hard and penetrating probes in high energy nucleus–nucleus collisions. The simulation consists of a time evolution model for the soft background, such as hydrodynamics, PYTHIA 8.1 to generate and hadronize the hard partons after the medium evolution, which is based on the McGill-AMY formalism and includes both radiative and elastic processes. MARTINI allows for the generation of full event configurations in the high \(p_{\rm T}\) region. We present results for the neutral pion and photon nuclear modification factor in Au+Au collisions at RHIC.


Diquark Bose–Einstein Condensation at Strong Coupling

abstract

We investigate the phase structure of the SU\(_f(2)\otimes \,{\rm SU}_c(3)\) Nambu–Jona-Lasinio model as a function of the scalar diquark coupling strength. Above a critical coupling, the binding energy is sufficiently large to overcompensate the quark masses and a massless scalar diquark bound state emerges which leads to Bose condensation already in the vacuum.


top

ver. 2024.03.17 • we use cookies and MathJax