Thermal hadron production in pp and p{\bar p} collisions

It is shown that the hadron production in high energy pp and p{\bar p} collisions, calculated by assuming that particles originate in hadron gas fireballs at thermal and partial chemical equilibrium, agrees very well with the data. The temperature of the hadron gas fireballs, determined by fitting hadron abundances, does not seem to depend on the centre of mass energy, having a nearly constant value of about 170 MeV. This value is in agreement with that obtained in e^+e^- collisions and supports a universal hadronization mechanism in all kinds of reactions consisting in a parton-hadron transition at critical values of temperature and pressure.Comment: 41 pages, 11 .eps figures, published in Z. Phys. C Revision - Corrections of two formulae in Sect.

Air transport in Africa: toward sustainable business models for African airlines

Although there is a vast amount of literature on airline business models and their evolution in changing global landscapes, there is a general lack of research into the applicability of those models, traditionally defined in European and North American contexts, to the African scene. Implicit in this study is the hypothesis that the African environment is unique enough to warrant its own host of strategies, which may be distinctive enough to form part of a new strategic template, or business model. Initially, a review of existing literature is undertaken to profile the African aviation environment and evaluate existing airline business models and their evolution, both globally and in Africa. The methodology consists firstly of a cluster exercise, whereby 57 African airlines are analysed in terms of their network and size, to yield a number of heterogeneous groups which serve to identify the current business models of airlines on the continent. Following this, eight airlines (representative of the groups outlined in the cluster analysis) were subsequently selected for analysis in terms of the Product and Organisational Architecture framework. While it was evident that the traditional models are followed in Africa, in some instances variations were apparent. Full-service network carriers and regional carriers were concluded as being the most prominent and stable in the African market. The applicability of the low-cost carrier model in Africa was also examined at length, with mixed results. The analysis also raised network density and connectivity as essential components of business models for delivering profits in an African context

Equation of State and Collective Dynamics

This talk summarizes the present status of a program to quantitatively relate data from the Relativistic Heavy Ion Collider (RHIC) on collective expansion flow to the Equation of State (EOS) of hot and dense strongly interacting matter, including the quark-gluon plasma and the quark-hadron phase transition. The limits reached with the present state of the art and the next steps required to make further progress will both be discussed.Comment: 8 pages, 6 two-part figures. Invited talk given at the 5th International Conference on the Physics and Astrophysics of Quark-Gluon Plasma (ICPAQGP 2005), Kolkata (India), Feb 8-12, 2005. Proceedings to be published in Journal of Physics: Conference Series (Jan-E Alam et al., eds.

Evolution of pion HBT radii from RHIC to LHC -- Predictions from ideal hydrodynamics

We present hydrodynamic predictions for the charged pion HBT radii for a range of initial conditions covering those presumably reached in Pb+Pb collisions at the LHC. We study central (b=0) and semi-central (b=7fm) collisions and show the expected increase of the HBT radii and their azimuthal oscillations. The predicted trends in the oscillation amplitudes reflect a change of the final source shape from out-of-plane to in-plane deformation as the initial entropy density is increased.Comment: 6 pages, incl. 5 figures. Contribution to the CERN Theory Institute Workshop "Heavy Ion Collisions at the LHC -- Last Call for Predictions", CERN, 14 May - 8 June 2007, to appear in J. Phys.

Fitted HBT radii versus space-time variances in flow-dominated models

The inability of otherwise successful dynamical models to reproduce the ``HBT radii'' extracted from two-particle correlations measured at the Relativistic Heavy Ion Collider (RHIC) is known as the ``RHIC HBT Puzzle.'' Most comparisons between models and experiment exploit the fact that for Gaussian sources the HBT radii agree with certain combinations of the space-time widths of the source which can be directly computed from the emission function, without having to evaluate, at significant expense, the two-particle correlation function. We here study the validity of this approach for realistic emission function models some of which exhibit significant deviations from simple Gaussian behaviour. By Fourier transforming the emission function we compute the 2-particle correlation function and fit it with a Gaussian to partially mimic the procedure used for measured correlation functions. We describe a novel algorithm to perform this Gaussian fit analytically. We find that for realistic hydrodynamic models the HBT radii extracted from this procedure agree better with the data than the values previously extracted from the space-time widths of the emission function. Although serious discrepancies between the calculated and measured HBT radii remain, we show that a more ``apples-to-apples'' comparison of models with data can play an important role in any eventually successful theoretical description of RHIC HBT data.Comment: 12 pages, 16 color figure

Early thermalization at RHIC

It is shown that recent RHIC data on hadron spectra and elliptic flow can be excellently reproduced within a hydrodynamic description of the collision dynamics, and that this provides strong evidence for rapid thermalization while the system is still in the quark-gluon plasma phase. But even though the hydrodynamic approach provides an impressive description of the single-particle momentum distributions, it fails to describe the two-particle momentum correlation (HBT) data for central Au+Au collisions at RHIC. We suggest that this is not likely to be repaired by further improvements in our understanding of the early collision stages, but probably requires a better modelling of the freeze-out process. We close with a prediction of the phases of the azimuthal oscillations of the HBT radii in noncentral collisions at RHIC.Comment: 12 pages, including 6 figures. Invited talk at the International Conference on "Statistical QCD", Bielefeld, August 26-30, 2001, to appear in the proceedings (F. Karsch and H. Satz, eds.) in Nucl. Phys.