The dependence of strange hadron multiplicities on the speed of hadronization

Hadron multiplicities are calculated in the ALCOR model for the Pb+Pb collisions at CERN SPS energy. Considering the newest experimental results, we display our prediction obtained from the ALCOR model for stable hadrons including strange baryons and anti-baryons.Comment: 8 pages, LaTeX in IOP style, appeared in the Proceedings of Strangeness'97 Conference, Santorini, April 14-18 1997, J. of Physics G23 (1997) 194

Hard and soft probe - medium interactions in a 3D hydro+micro approach at RHIC

We utilize a 3D hybrid hydro+micro model for a comprehensive and consistent description of soft and hard particle production in ultra-relativistic heavy-ion collisions at RHIC. In the soft sector we focus on the dynamics of (multi-)strange baryons, where a clear strangeness dependence of their collision rates and freeze-out is observed. In the hard sector we study the radiative energy loss of hard partons in a soft medium in the multiple soft scattering approximation. While the nuclear suppression factor $R_{AA}$ does not reflect the high quality of the medium description (except in a reduced systematic uncertainty in extracting the quenching power of the medium), the hydrodynamical model also allows to study different centralities and in particular the angular variation of $R_{AA}$ with respect to the reaction plane, allowing for a controlled variation of the in-medium path-length.Comment: 5 pages, 4 figures, Quark Matter 2006 proceedings, to appear in Journal of Physics

Observing Quark-Gluon Plasma with Strange Hadrons

We review the methods and results obtained in an analysis of the experimental heavy ion collision research program at nuclear beam energy of 160-200A GeV. We study strange, and more generally, hadronic particle production experimental data. We discuss present expectations concerning how these observables will perform at other collision energies. We also present the dynamical theory of strangeness production and apply it to show that it agrees with available experimental results. We describe strange hadron production from the baryon-poor quark-gluon phase formed at much higher reaction energies, where the abundance of strange baryons and antibaryons exceeds that of nonstrange baryons and antibaryons.Comment: 39 journal pages (155kb text), 8 postscript figures, 8 table

Irreversible nucleation in molecular beam epitaxy: From theory to experiments

Recently, the nucleation rate on top of a terrace during the irreversible growth of a crystal surface by MBE has been determined exactly. In this paper we go beyond the standard model usually employed to study the nucleation process, and we analyze the qualitative and quantitative consequences of two important additional physical ingredients: the nonuniformity of the Ehrlich-Schwoebel barrier at the step-edge, because of the existence of kinks, and the steering effects, due to the interaction between the atoms of the flux and the substrate. We apply our results to typical experiments of second layer nucleation.Comment: 11 pages. Table I corrected and one appendix added. To be published in Phys. Rev. B (scheduled issue: 15 February 2003

Hadronization of massive quark matter

We present a fast hadronization model for the constituent quark plasma (CQP) produced in relativistic heavy ion collisions at SPS. The model is based on rate equations and on an equation of state inspired by the string phenomenology. This equation of state has a confining character. We display the time evolution of the relevant physical quantities during the hadronization process and the final hadron multiplicities. The results indicate that the hadronization of CQP is fast.Comment: 12 pages, Latex, 2 EPS figures, contribution to the Proceedings of the 4th International Conference on Strangeness in Quark Matter (SQM'98), Padova, Italy, 20-24 July 199

Phase Transitions Driven by Vortices in 2D Superfluids and Superconductors: From Kosterlitz-Thouless to 1st Order

The Landau-Ginzburg-Wilson hamiltonian is studied for different values of the parameter $\lambda$ which multiplies the quartic term (it turns out that this is equivalent to consider different values of the coherence length $\xi$ in units of the lattice spacing $a$). It is observed that amplitude fluctuations can change dramatically the nature of the phase transition: for small values of $\lambda$ ($\xi/a > 0.7$), instead of the smooth Kosterlitz-Thouless transition there is a {\em first order} transition with a discontinuous jump in the vortex density $v$ and a larger non-universal drop in the helicity modulus. In particular, for $\lambda$ sufficiently small ($\xi/a \cong 1$), the density of bound pairs of vortex-antivortex below $T_c$ is so low that, $v$ drops to zero almost for all temperature $T<Tc$.Comment: 8 pages, 5 .eps figure

Genetic Variance and Covariance Components for Feed Intake, Average Daily Gain, and Postweaning Gain in Growing Beef Cattle

Feed is the greatest cost for a beef cattle production enterprise. Data collection to determine feed efficiency of animals is also costly, because both gain and intake records are needed to calculate feed efficiency. Electronic intake monitoring systems such as GrowSafe or Insentec to collect feed intake data are expensive and thus limit the number of animals that can be tested. Scientists have worked to pinpoint optimal test durations for collecting both weight gain and feed intake records to lessen costs. A 70-day performance test is currently recommended for accurate calculation of efficiency, with growth data as the limiting factor. Research has suggested that a 35-day test is adequate to measure feed intake, but a test period of at least 70 days is suggested to measure gain with sufficient accuracy. The objective of this study was to estimate genetic parameters for growth and intake traits with particular attention to the relationship between on-test average daily gain (ADG) and national cattle evaluation postweaning gain (PWG). If the correlation between these two traits is strong, it could allow for the use of PWG as a proxy for ADG in the genetic evaluation of feed efficiency. This substitution would allow producers to reduce the length of the test required to measure feed intake accurately

Remnants of Initial Anisotropic High Energy Density Domains in Nucleus-Nucleus Collisions

Anisotropic high energy density domains may be formed at early stages of ultrarelativistic heavy ion collisions, e.g. due to phase transition dynamics or non-equilibrium phenomena like (mini-)jets. Here we investigate hadronic observables resulting from an initially created anisotropic high energy density domain. Based on our studies using a transport model we find that the initial anisotropies are reflected in the freeze-out multiplicity distribution of both pions and kaons due to secondary hadronic rescattering. The anisotropy appears to be stronger for particles at high transverse momenta. The overall kaon multiplicity increases with large fluctuations of local energy densities, while no change has been found in the pion multiplicity.Comment: Submitted to PR

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