8 research outputs found
Analysis of kaon spectra at SIS energies - what remains from the KN potential
We study the reaction Au+Au at 1.48 AGeV and analyze the influence of the KN
optical potential on cm spectra and azimuthal distributions at mid-rapidity. We
find a significant change of the yields but only slight changes in the shapes
of the distributions when turning off the optical potential. However, the
spectra show contributions from different reaction times, where early kaons
contribute stronger to higher momenta and late kaons to lower momenta.
Azimuthal distributions of the kaons at mid-rapidity show a strong centrality
dependence. Their shape is influenced by the KN optical potential as well as by
re-scattering.Comment: SQM 2003 proceedings, 4 figures, 6 page
Hyperon production in Ar+KCl collisions at 1.76A GeV
We present transverse momentum spectra, rapidity distribution and
multiplicity of Lambda-hyperons measured with the HADES spectrometer in the
reaction Ar(1.76A GeV)+KCl. The yield of Xi- is calculated from our previously
reported Xi-/(Lambda+Sigma0) ratio and compared to other strange particle
multiplicities. Employing a strangeness balance equation the multiplicities of
the yet unmeasured charged Sigma hyperons can be estimated. Finally a
statistical hadronization model is used to fit the yields of pi-, K+, K0s, K-,
phi, Lambda and Xi-. The resulting chemical freeze-out temperature of T=(76+-2)
MeV is compared to the measured slope parameters obtained from fits to the
transverse mass distributions of the particles
Kaon properties in (proto)neutron stars
The modification on kaon and antikaon properties of in the interior of
(proto-)neutron stars is investigated using a chiral SU(3) model. The
parameters of the model are fitted to nuclear matter saturation properties,
baryon octet vacuum masses, hyperon optical potentials and low energy a
kaon-nucleon scattering lengths. We study the kaon/antikaon medium modification
and explore the possibility of antikaon condensation in (proto-)neutron star
matter at zero as well as finite temperature/entropy and neutrino content. The
effect of hyperons on kaon and antikaon optical potentials is also investigated
at different stages of the neutron star evolution.Comment: 17 pages including 4 figure
Recent astrophysical and accelerator based results on the Hadronic Equation of State
In astrophysics as well as in hadron physics progress has recently been made
on the determination of the hadronic equation of state (EOS) of compressed
matter. The results are contradictory, however. Simulations of heavy ion
reactions are now sufficiently robust to predict the stiffness of the (EOS)
from (i) the energy dependence of the ratio of from Au+Au and C+C
collisions and (ii) the centrality dependence of the multiplicities. The
data are best described with a compressibility coefficient at normal nuclear
matter density around 200 MeV, a value which is usually called
``soft'' The recent observation of a neutron star with a mass of twice the
solar mass is only compatible with theoretical predictions if the EOS is stiff.
We review the present situation.Comment: invited talk Strange Quark Matter Conference SQM06 in Los Angele