Status of Chemical Equilibrium in Relativistic Heavy Ion Collisions

Recent work on chemical equilibrium in heavy ion collisions is reviewed. The energy dependence of thermal parameters is discussed. The centrality dependence of thermal parameters at SPS energies is presented.Comment: 7 pages, 7 Postscript figure

Understanding K/πK/\pi ratio distribution in the mixed events

The event mixing method is analyzed for the study of the event-by-event $K/\pi$ ratio distribution. It is shown that there exists some correlation between the kaon and pion multiplicities in the mixed events. The $K/\pi$ ratio distributions in the mixed events for different sets of real events are shown. The dependence of the distributions on the mean $K/\pi$ ratio, mean and variance of multiplicity distribution in the real events is investigated systematically. The effect of imperfect particle identification on the $K/\pi$ ratio distribution in the mixed event is also considered.Comment: 11 pages in revtex, 8 eps figures include

Charge and Isospin Fluctuations in High Energy pp-Collisions

Charge and isospin event-by-event fluctuations in high-energy pp-collisions are predicted within the Unitary Eikonal Model, in particular the fluctuation patterns of the ratios of charged-to-charged and neutral-to-charged pions. These fluctuations are found to be sensitive to the presence of unstable resonances, such as $\rho$ and $\omega$ mesons. We predict that the charge-fluctuation observable $D_{UEM}$ should be restricted to the interval $8/3\le D_{UEM}\le 4$ depending on the $\rho /\pi$ production ratio. Also, the isospin fluctuations of the DCC-type of the ratio of neutral-to-charged pions are suppressed if pions are produced together with $\rho$ mesons.Comment: Latex, 5 pages, no figures. To appear in the proceedings of 9th Adriatic Meeting, Dubrovnik, Croatia, 4 - 14 September 2003. Added reference into reference no.

Scaling Distributions of Quarks, Mesons and Proton for all pTp_T, Energy and Centrality

We present the evidences for the existence of a universal scaling behavior of the production of $\pi^0$ at all transverse momenta in heavy-ion collisions at all centralities and all collision energies. The corresponding scaling behavior of the quarks is then derived just before the quarks recombine with antiquarks to form the pions. The degradation effect of the dense medium on the quark $p_T$ is derived from the scaling distribution. In the recombination model it is then possible to calculate the $p_T$ distributions of the produced proton and kaon, which are scaling also. Experimentally verifiable predictions are made. Implications of the existence of the scaling behavior are discussed.Comment: 10 pages in RevTeX, including 14 figures in eps file

A linear radiofrequency ion trap for accumulation, bunching, and emittance improvement of radioactive ion beams

An ion beam cooler and buncher has been developed for the manipulation of radioactive ion beams. The gas-filled linear radiofrequency ion trap system is installed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. Its purpose is to accumulate the 60-keV continuous ISOLDE ion beam with high efficiency and to convert it into low-energy low-emittance ion pulses. The efficiency was found to exceed 10% in agreement with simulations. A more than 10-fold reduction of the ISOLDE beam emittance can be achieved. The system has been used successfully for first on-line experiments. Its principle, setup and performance will be discussed

Resolving the Antibaryon-Production Puzzle in High-Energy Heavy-Ion Collisions

We argue that the observed antiproton production in heavy-ion collisions at CERN-SpS energies can be understood if (contrary to most sequential scattering approaches) the backward direction in the process $p\bar p \leftrightarrow \bar{n}\pi$ (with $\bar{n}$=5-6) is consistently accounted for within a thermal framework. Employing the standard picture of subsequent chemical and thermal freezeout, which induces an over-saturation of pion number with associated chemical potentials of $\mu_\pi\simeq$~60-80 MeV, enhances the backward reaction substantially. The resulting rates and corresponding cross sections turn out to be large enough to maintain the abundance of antiprotons at chemical freezeout until the decoupling temperature, in accord with the measured $\bar{p}/p$ ratio in Pb(158AGeV)+Pb collisions.Comment: 4 pages ReVTeX incl. 2 eps-figs, minor changes (two figs added, rate eq. written more explicitly), version accepted for publication in PR

Hadro-Chemistry and Evolution of (Anti-) Baryon Densities at RHIC

The consequences of hadro-chemical freezeout for the subsequent hadron gas evolution in central heavy-ion collisions at RHIC and LHC energies are discussed with special emphasis on effects due to antibaryons. Contrary to naive expectations, their individual conservation, as implied by experimental data, has significant impact on the chemical off-equilibrium composition of hadronic matter at collider energies. This may reflect on a variety of observables including source sizes and dilepton spectra.Comment: 4 pages ReVTeX incl. 3 ps-figs, submitted to PR

System-size dependence

The final state in The final state in heavy-ion collisions has a higher degree of strangeness saturation than the one produced in collisions between elementary particles like p-p or p-$\bar{p}$. A systematic analysis of this phenomenon is made for C-C, Si-Si and Pb-Pb collisions at the CERN SPS collider and for $Au-Au$ collisions at RHIC and at AGS energies. Strangeness saturation is shown to increase smoothly with the number of participants at AGS, CERN and RHIC energies.Comment: 5 pages, 5 figures, presented at SQM2003 conferenc

A linear radiofrequency quadrupole ion trap for the cooling and bunching of radioactive ion beams

A linear radiofrequency quadrupole ion guide and beam buncher has been installed at the ISOLTRAP mass spectrometry experiment at the ISOLDE facility at CERN. The apparatus is being used as a beam cooling, accumulation, and bunching system. It operates with a buffer gas that cools the injected ions and converts the quasicontinuous 60- keV beam from the ISOLDE facility to 2.5-keV beam pulses with improved normalized transverse emittance. Recent measurements suggest a capture efficiency of the ion guide of up to 40% and a cooling and bunching efficiency of at least 12% which is expected to still be increased. The improved ISOLTRAP setup has so far been used very successfully in three on-line experiments. (12 refs)

Strangeness, Charm and Beauty in Quark Matter: SQM 2007 Experimental Overview

This paper aims at providing an experimental overview of the Strangeness in Quark Matter 2007 ConferenceComment: Proceedings of Strangeness in Quark Matter 2007, submitted to Journal of Physics