Secondary phi meson peak as an indicator of QCD phase transition in ultrarelativistic heavy ion collisions

In a previous paper, we have shown that a double phi peak structure appears in the dilepton invariant mass spectrum if a first order QCD phase transition occurs in ultrarelativistic heavy ion collisions. Furthermore, the transition temperature can be determined from the transverse momentum distribution of the low mass phi peak. In this work, we extend the study to the case that a smooth crossover occurs in the quark-gluon plasma to the hadronic matter transition. We find that the double phi peak structure still exists in the dilepton spectrum and thus remains a viable signal for the formation of the quark-gluon plasma in ultrarelativistic heavy ion collisions.Comment: 8 pages, 9 uuencoded postscript figures included, Latex, LBL-3572

Critique of a Pion Exchange Model for Interquark Forces

I describe four serious defects of a widely discussed pion exchange model for interquark forces: it doesn't solve the "spin-orbit problem" as advertised, it fails to describe the internal structure of baryon resonances, it leads to disastrous conclusions when extended to mesons, and it is not reasonably connected to the physics of heavy-light systems.Comment: 20 pages, 6 figures; some clarifications and references adde

Analytic Approach to Perturbative QCD

The two-loop invariant (running) coupling of QCD is written in terms of the Lambert W function. The analyticity structure of the coupling in the complex Q^2-plane is established. The corresponding analytic coupling is reconstructed via a dispersion relation. We also consider some other approximations to the QCD beta-function, when the corresponding couplings are solved in terms of the Lambert function. The Landau gauge gluon propagator has been considered in the renormalization group invariant analytic approach (IAA). It is shown that there is a nonperturbative ambiguity in determination of the anomalous dimension function of the gluon field. Several analytic solutions for the propagator at the one-loop order are constructed. Properties of the obtained analytical solutions are discussed.Comment: Latex-file, 19 pages, 2 tables, 51 references, to be published in Int. J. Mod. Phys.

Hadronic observables from SIS to SPS energies - anything strange with strangeness ?

We calculate $p, \pi^\pm, K^\pm$ and $\Lambda$(+$\Sigma^0$) rapidity distributions and compare to experimental data from SIS to SPS energies within the UrQMD and HSD transport approaches that are both based on string, quark, diquark ($q, \bar{q}, qq, \bar{q}\bar{q}$) and hadronic degrees of freedom. The two transport models do not include any explicit phase transition to a quark-gluon plasma (QGP). It is found that both approaches agree rather well with each other and with the experimental rapidity distributions for protons, $\Lambda$'s, $\pi^\pm$ and $K^\pm$. Inspite of this apparent agreement both transport models fail to reproduce the maximum in the excitation function for the ratio $K^+/\pi^+$ found experimentally between 11 and 40 A$\cdot$GeV. A comparison to the various experimental data shows that this 'failure' is dominantly due to an insufficient description of pion rapidity distributions rather than missing 'strangeness'. The modest differences in the transport model results -- on the other hand -- can be attributed to different implementations of string formation and fragmentation, that are not sufficiently controlled by experimental data for the 'elementary' reactions in vacuum.Comment: 46 pages, including 15 eps figures, to be published in Phys. Rev.

Dynamics of Hot Bulk QCD Matter: from the Quark-Gluon Plasma to Hadronic Freeze-Out

We introduce a combined macroscopic/microscopic transport approach employing relativistic hydrodynamics for the early, dense, deconfined stage of the reaction and a microscopic non-equilibrium model for the later hadronic stage where the equilibrium assumptions are not valid anymore. Within this approach we study the dynamics of hot, bulk QCD matter, which is expected to be created in ultra-relativistic heavy ion collisions at the SPS, the RHIC and the LHC. Our approach is capable of self-consistently calculating the freeze-out of the hadronic system, while accounting for the collective flow on the hadronization hypersurface generated by the QGP expansion. In particular, we perform a detailed analysis of the reaction dynamics, hadronic freeze-out, and transverse flow.Comment: 55 pages, 15 figure

QGP Theory: Status and Perspectives

The current status of Quark-Gluon-Plasma Theory is reviewed. Special emphasis is placed on QGP signatures, the interpretation of current data and what to expect from RHIC in the near future.Comment: 20 pages, invited overview talk at the 4th International Conference on the Physcis and Astrophysics of the Quark-Gluon-Plasma, November 2001, Jaipur, India, to appear in Praman

Space-time evolution and HBT analysis of relativistic heavy ion collisions in a chiral SU(3) x SU(3) model

The space-time dynamics and pion-HBT radii in central heavy ion-collisions at CERN-SPS and BNL-RHIC are investigated within a hydrodynamic simulation. The dependence of the dynamics and the HBT-parameters on the EoS is studied with different parametrisations of a chiral SU(3) sigma-omega model. The selfconsistent collective expansion includes the effects of effective hadron masses, generated by the nonstrange and strange scalar condensates. Different chiral EoS show different types of phase transitions and even a crossover. The influence of the order of the phase transition and of the difference in the latent heat on the space-time dynamics and pion-HBT radii is studied. A small latent heat, i.e. a weak first-order chiral phase transition, or even a smooth crossover leads to distinctly different HBT predictions than a strong first order phase transition. A quantitative description of the data, both at SPS energies as well as at RHIC energies, appears difficult to achieve within the ideal hydrodynamical approach using the SU(3) chiral EoS. A strong first-order quasi-adiabatic chiral phase transition seems to be disfavored by the pion-HBT data from CERN-SPS and BNL-RHIC

Signatures of Quark-Gluon-Plasma formation in high energy heavy-ion collisions: A critical review

A critical review on signatures of Quark-Gluon-Plasma formation is given and the current (1998) experimental status is discussed. After giving an introduction to the properties of QCD matter in both, equilibrium- and non-equilibrium theories, we focus on observables which may yield experimental evidence for QGP formation. For each individual observable the discussion is divided into three sections: first the connection between the respective observable and QGP formation in terms of the underlying theoretical concepts is given, then the relevant experimental results are reviewed and finally the current status concerning the interpretation of both, theory and experiment, is discussed. A comprehensive summary including an outlook towards RHIC is given in the final section.Comment: Topical review, submitted to Journal of Physics G: 68 pages, including 39 figures (revised version: only minor modifications, some references added

Cluster Transformation Coefficients for Structure and Dynamics Calculations in n-Particle Systems: Atoms, Nuclei, and Quarks

The structure and dynamics of an n-particle system are described with coupled nonlinear Heisenberg's commutator equations where the nonlinear terms are generated by the two-body interaction that excites the reference vacuum via particle-particle and particle-hole excitations. Nonperturbative solutions of the system are obtained with the use of dynamic linearization approximation and cluster transformation coefficients. The dynamic linearization approximation converts the commutator chain into an eigenvalue problem. The cluster coefficients factorize the matrix elements of the (n)-particles or particle-hole systems in terms of the matrix elements of the (n-1)-systems coupled to a particle-particle, particle-hole, and hole-hole boson. Group properties of the particle-particle, particle-hole, and hole-hole permutation groups simplify the calculation of these coefficients. The particle-particle vacuum-excitations generate superconductive diagrams in the dynamics of 3-quarks systems. Applications of the model to fermionic and bosonic systems are discussed.Comment: 13 pages, 5 figures, Wigner Proceedings for Conference Wigner Centenial Pecs, July 8-12, 200

Octopus Engagement: Educating Through Involvement

The purpose of our project is to showcase our group presentation that we arranged as a part of our Marine Conservation and Restoration course. We went to Goldsboro Elementary School to visit a class of third-grade students in their science class. As a group, we shared what we knew about octopuses so they could take a step into the world of marine biology. Our presentation consisted of fascinating facts and fun visual aids that captivated the students and allowed them to form a deeper connection with the octopus. To enhance their learning, we organized four fun activities, one being a spin on simon says called “octopus says”, another being an octopus scavenger hunt, while also personalizing an octopus tentacle to attach to a classroom poster. Finally, each of them created their own octopus hat. A pre and post-test was also completed to see what the students took away from our presentation. Overall, this experience highlighted the importance of interactive learning and inspiring young minds in the classroom.https://stars.library.ucf.edu/hip-2024fall/1041/thumbnail.jp