12 research outputs found
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
production sensitive to the nuclear equation of state? b) How can it happen
that at the same excess energy the same number of and 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
On the exact conservation laws in thermal models and the analysis of AGS and SIS experimental results
The production of hadrons in relativistic heavy ion collisions is studied
using a statistical ensemble with thermal and chemical equilibrium. Special
attention is given to exact conservation laws, i.e. certain charges are treated
canonically instead of using the usual grand canonical approach. For small
systems, the exact conservation of baryon number, strangeness and electric
charge is to be taken into account. We have derived compact, analytical
expressions for particle abundances in such ensemble. As an application, the
change in ratios in AGS experiments with different interaction system
sizes is well reproduced. The canonical treatment of three charges becomes
impractical very quickly with increasing system size. Thus, we draw our
attention to exact conservation of strangeness, and treat baryon number and
electric charge grand canonically. We present expressions for particle
abundances in such ensemble as well, and apply them to reproduce the large
variety of particle ratios in GSI SIS 2 A GeV Ni-Ni experiments. At the
energies considered here, the exact strangeness conservation fully accounts for
strange particle suppression, and no extra chemical factor is needed.Comment: Talk given at Strangeness in Quark Matter '98, Padova, Italy (1998).
Submitted to J.Phys. G. 5 pages, 2 figure
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
Enhanced Out-of-plane Emission of K+ Mesons observed in Au+Au Collisions at 1 AGeV
The azimuthal angular distribution of K+ mesons has been measured in Au + Au
collisions at 1 AGeV. In peripheral and semi-central collisions, K+ mesons
preferentially are emitted perpendicular to the reaction plane. The strength of
the azimuthal anisotropy of K+ emission is comparable to the one of pions. No
in-plane flow was found for K+ mesons near projectile and target rapidity.Comment: Accepted for publication in Phys. Rev.Let
Strangeness at SIS energies
In this contribution we discuss the physics of strange hadrons in low energy
() heavy ion collision. In this energy range the relevant
strange particle are the kaons and anti-kaons. The most interesting aspect
concerning these particles are so called in-medium modifications. We will
attempt to review the current status of understanding of these in medium
modifications. In addition we will briefly discuss other issues related with
kaon production, such as the nuclear equation of state and chemical
equilibrium.Comment: Proceedings Strange Quark Matter 2003, Atlantic Beach, NC, USA, March
200
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