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Results are presented on Omega production in central Pb+Pb collisions at 40 and 158 AGeV beam energy. Given are transverse-mass spectra, rapidity distributions, and total yields for the sum Omega+Antiomega at 40 AGeV and for Omega and Antiomega separately at 158 AGeV. The yields are strongly under-predicted by the string-hadronic UrQMD model and are in better agreement with predictions from a hadron gas models. PACS numbers: 25.75.Dw
Vortrag gehalten am 12. Januar 2005 in Frankfurt am Main, am Physikalischen Verein, anläßlich der Verleihung des Philipp-Siedler-Wissenschaftspreises an Dipl.-Phys. Christine Meurer, als Anerkennung für ihre Diplomarbeit "Xi- und Xi+ Produktion in Pb+Pb Stößen bei 40 A GeV am CERN SPS" (urn:nbn:de:hebis:30-13740). Am CERN, dem Europäischen Kernforschungszentrum, werden Bleiatomkerne auf nahezu Lichtgeschwindigkeit beschleunigt und zur Kollision gebracht. Dabei wird die Materie in einer Art Feuerball extrem verdichtet und erhitzt. Unter diesen Bedingungen brechen die Bestandteile der Atomkerne, die Nukleonen, auf und der Blick auf die eigentlichen Bausteine der Materie, die Quarks, wird möglich. Nach der Kollision expandiert der Feuerball und viele neue Teilchen, darunter auch die sogenannten seltsamen Teilchen, entstehen. Ihre Besonderheiten werden im Vortrag diskutiert: Ergebnisse zur Produktion des seltsamen Xi- -Teilchens in Pb+Pb-Stößen bei einer Energie von 40 A GeV werden vorgestellt. Aus dem transversalen Massenspektrum bei mittlerer Rapidität erhält man einen inversen Steigungsparamenter von T Xi- = (210±11±21)MeV . Die Integration des Rapiditätsspektrums liefert eine totale Anzahl der s im gesamten Phasenraum von (2.41 ± 0.15 ± 0.24) Teilchen pro Kollision. Desweiteren wird die Anregungsfunktion des Xi- -Hyperons sowie seine Zentralitätsabhänigkeit bei 40 A GeV diskutiert.
System-size dependence of strangeness production in nucleus-nucleus collisions at √sNN = 17.3 GeV
(2005)
Emission of pi, K, phi and Lambda was measured in near-central C+C and Si+Si collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S and Pb+Pb, the system-size dependence of relative strangeness production in nucleus-nucleus collisions is obtained. Its fast rise and the saturation observed at about 60 participating nucleons can be understood as onset of the formation of coherent partonic subsystems of increasing size. PACS numbers: 25.75.-q
Electric charge correlations were studied for p+p, C+C, Si+Si, and centrality selected Pb+Pb collisions at sqrt[sNN]=17.2 GeV with the NA49 large acceptance detector at the CERN SPS. In particular, long-range pseudorapidity correlations of oppositely charged particles were measured using the balance function method. The width of the balance function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions.
Particle production in central Pb+Pb collisions was studied with the NA49 large acceptance spectrometer at the CERN SPS at beam energies of 20, 30, 40, 80, and 158 GeV per nucleon. A change of the energy dependence is observed around 30A GeV for the yields of pions and strange particles as well as for the shapes of the transverse mass spectra. At present only a reaction scenario with onset of deconfinement is able to reproduce the measurements.
Using CORSIKA for simulating extensive air showers, we study the relation between the shower characteristics and features of hadronic multiparticle production at low energies. We report about investigations of typical energies and phase space regions of secondary particles which are important for muon production in extensive air showers. Possibilities to measure relevant quantities of hadron production in existing and planned accelerator experiments are discussed.