42 research outputs found
Schwellennahe Erzeugung von Kaonen und Antikaonen in Proton-Kern-Stößen
Am Schwerionensynchrotron der GSI Darmstadt wurde die Produktion von K- und pi-Mesonen in Proton-Kern-Kollisionen ("pA") experimentell untersucht. Verschiedene Targetkerne (C, Au), Strahlenergien (1.6, 2.5, 3.5 GeV) und Beobachtungswinkel (32°-64°) ergaben eine reichhaltige Systematik und gestatteten Extrapolationen auf totale Wirkungsquerschnitte. In der Arbeit werden Vergleiche der einzelnen Messungen miteinander und mit pA-Messungen anderer Gruppen angestellt und diskutiert. Die Einordnung zwischen pp- und AA-Daten und der Vergleich mit theoretischen Vorhersagen ermöglicht grundlegende Aussagen über das Verhalten von K-Mesonen in Kernmaterie, sogenannte Medium-Effekte
Particle production and chemical freezeout from the hybrid UrQMD approach at NICA energies
The energy dependence of various particle ratios is calculated within the
Ultra-Relativistic Quantum Molecular Dynamics approach and compared with the
hadron resonance gas (HRG) model and measurements from various experiments,
including RHIC-BES, SPS and AGS. It is found that the UrQMD particle ratios
agree well with the experimental results at the RHIC-BES energies. Thus, we
have utilized UrQMD in simulating particle ratios at other beam energies down
to 3 GeV, which will be accessed at NICA and FAIR future facilities. We observe
that the particle ratios for crossover and first-order phase transition,
implemented in the hybrid UrQMD v3.4, are nearly indistinguishable, especially
at low energies (at large baryon chemical potentials or high density).Comment: 13 pages, 5 figures, 2 tables, one reference is added and one
paragraph is rephrased. To appear in EPJ
Entropy per rapidity in Pb-Pb central collisions using Thermal and Artificial neural network(ANN) models at LHC energies
The entropy per rapidity produced in central Pb-Pb
ultra-relativistic nuclear collisions at LHC energies is calculated using
experimentally observed identified particle spectra and source radii estimated
from Hanbury Brown-Twiss (HBT) for particles, , , , ,
, and , and , , , and at and TeV, respectively. Artificial neural network (ANN)
simulation model is used to estimate the entropy per rapidity at the
considered energies. The simulation results are compared with equivalent
experimental data, and good agreement is achieved. A mathematical equation
describes experimental data is obtained. Extrapolating the transverse momentum
spectra at is required to calculate thus we use two
different fitting functions, Tsallis distribution and the Hadron Resonance Gas
(HRG) model. The success of ANN model to describe the experimental measurements
will imply further prediction for the entropy per rapidity in the absence of
the experiment
Contribution of the nucleon-hyperon reaction channels to K production in proton-nucleus collisions
The cross sections for producing K mesons in nucleon-hyperon elementary
processes are estimated assuming one-pion exchange and using the experimentally
known pion-hyperon cross sections. The results are implemented in a transport
model which is applied to calculation of proton-nucleus collisions. In
significant difference to earlier estimates for heavy-ion collisions the
inclusion of the nucleon-hyperon cross section roughly doubles the K
production in near-threshold proton-nucleus collisions
Overview of Antikaon-Nuclear Quasi-Bound States
Experimental evidence for antikaon-nuclear quasi-bound states is briefly
reviewed. Theoretical and phenomenological arguments for and against the
existence of such states are considered, based on constructing antikaon-nuclear
optical potentials from various sources. Results of RMF calculations that
provide a lower limit of Gamma(antikaon) = 50 +/- 10 MeV on the width of
antikaon-nuclear quasi-bound states are discussed.Comment: Plenary talk given at FB18, Santos, Brazil, August 2006, to be
published in the Proceedings, Nucl. Phys. A. Overview updated to the
aftermath of HYP06 in which the experimental claims for strange tribaryons
were withdraw
Kaon and Antikaon Production in Heavy Ion Collisions at 1.5 AGeV
At the Kaon Spectrometer KaoS at SIS, GSI the production of kaons and
antikaons in heavy ion reactions at a beam energy of 1.5 AGeV has been measured
for the collision systems Ni+Ni and Au+Au. The K-/K+ ratio is found to be
constant for both systems and as a function of impact parameter but the slopes
of K+ and K- spectra differ for all impact parameters. Furthermore the
respective polar angle distributions will be presented as a function of
centrality.Comment: 4 pages, 4 figures, SQM2001 in Frankfurt, Sept.2001, submitted to
Journal of Physics
The role of three-body collisions in phi-meson production processes near threshold
The amplitude of subthreshold phi-meson production is calculated using
dominant tree-level diagrams for three-body collisions. It is shown that the
production can overwhelmingly be described by two-step processes. The effect of
the genuine three-body contribution (i.e. the contribution which cannot be
factorized) is discussed. The production rate of phi-mesons is presented for
proton induced reactions on carbon.Comment: 19 page
K+ and K- production in heavy-ion collisions at SIS-energies
The production and the propagation of K+ and of K- mesons in heavy-ion
collisions at beam energies of 1 to 2 AGeV have systematically been
investigated with the Kaon Spectrometer KaoS at the SIS at the GSI. The ratio
of the K+ production excitation function for Au+Au and for C+C reactions
increases with decreasing beam energy, which is expected for a soft nuclear
equation-of-state. At 1.5 AGeV a comprehensive study of the K+ and of the K-
emission as a function of the size of the collision system, of the collision
centrality, of the kaon energy, and of the polar emission angle has been
performed. The K-/K+ ratio is found to be nearly constant as a function of the
collision centrality. The spectral slopes and the polar emission patterns are
different for K- and for K+. These observations indicate that K+ mesons
decouple earlier from the reaction zone than K- mesons.Comment: invited talk given at the SQM2003 conference in Atlantic Beach, USA
(March 2003), to be published in Journal of Physics G, 10pages, 7 figure