Strange Particle Production in pp Collisions at sqrt(s) = 0.9 and 7 TeV measured with the ALICE Experiment

Hadrons measured in proton-proton collisions at sqrt(s) = 0.9 and 7 TeV with the ALICE detector have been identified using various techniques: the specific energy loss and the time-of flight information for charged pions, kaons and protons, the displaced vertex resulting from their weak decay for K0, Lambda and Xi and the kink topology of decaying charged kaons. These various particle identification tools give the best separation at different momentum ranges and the results are combined to obtain spectra from pt = 100 MeV/c to 2.5 GeV/c. This allows to extract total yields. In detail we discuss the K/pi ratio together with previous measurements and we show a fit using a statistical approach.Comment: 4 pages, 3 figures, Proceedings of the ICPAQGP2010 conference in Goa, India, December 6th - 10th, 201

Statistical Model and the mesonic-baryonic transition region

The statistical model assuming chemical equilibriumand local strangeness conservation describes most of the observed features of strange particle production from SIS up to RHIC. Deviations are found as the maximum in the measured K+/pi+ ratio is much sharper than in the model calculations. At the incident energy of the maximum, the statistical model shows that freeze out changes regime from one being dominated by baryons at the lower energies toward one being dominated by mesons. It will be shown how deviations from the usual freeze-out curve influence the various particle ratios. Furthermore, other observables exhibit also changes just in this energy regime.Comment: 9 pages, 7 figures, CPOD conference proceeding

Conservation Laws and Particle Production in Heavy Ion Collisions

We discuss the role of the conservation laws related with U(1) internal symmetry group in the statistical model description of particle productions in ultrarelativistic heavy ion collisions. We derive and show the differences in particle multiplicities in the canonical and the grand canonical formulation of quantum number conservation. The time evolution and the approach to chemical equilibrium in the above ensembles is discussed in terms of kinetic master equation. The application of the statistical model to the description of (multi)strange particle yields at GSI/SIS and the SPS energies is also presented.Comment: Invited talk at International Symposium on Hadron and Nuclei, Seoul, Korea, 20-22 Feb 200

On the chemical equilibration of strangeness-exchange reaction in heavy-ion collisions

The strangeness-exchange reaction pi + Y -> K- + N is shown to be the dynamical origin of chemical equilibration for K- production in heavy-ion collisions up to beam energies of 10 A GeV. The hyperons occurring in this process are produced associately with K+ in baryon-baryon and meson-baryon interactions. This connection is demonstrated by the ratio K-/K+ which does not vary with centrality and shows a linear correlation with the yield of pions per participant. At incident energies above AGS this correlation no longer holds due to the change in the production mechanism of kaons.Comment: 9 pages, 4 figure

Kaon production at subthreshold and threshold energies

We summarize what we have learnt about the kaon production in nucleus-nucleus collisions in the last decade. We will address three questions: a) Is the $K^+$ production sensitive to the nuclear equation of state? b) How can it happen that at the same excess energy the same number of $K^+$ and $K^-$ are produced in heavy ion collisions although the elementary cross section in pp collisions differs by orders of magnitudes? and c) Why kaons don't flow?Comment: 5 pages, 4 figures, contribution to Strange Quark Matter 200