454 research outputs found
Radial flow has little effect on clusterization at intermediate energies in the framework of the Lattice Gas Model
The Lattice Gas Model was extended to incorporate the effect of radial flow.
Contrary to popular belief, radial flow has little effect on the clusterization
process in intermediate energy heavy-ion collisions except adding an ordered
motion to the particles in the fragmentation source. We compared the results
from the lattice gas model with and without radial flow to experimental data.
We found that charge yields from central collisions are not significantly
affected by inclusion of any reasonable radial flow.Comment: 8 pages, 2 figures, submitted to PRC; Minor update and resubmitted to
PR
Cavitation and bubble collapse in hot asymmetric nuclear matter
The dynamics of embryonic bubbles in overheated, viscous and non-Markovian
nuclear matter is studied. It is shown that the memory and the Fermi surface
distortions significantly affect the hinderance of bubble collapse and
determine a characteristic oscillations of the bubble radius. These
oscillations occur due to the additional elastic force induced by the memory
integral.Comment: Revtex file (10 pages) and 3 figure
Thermal Hadron Production in High Energy Heavy Ion Collisions
We provide a method to test if hadrons produced in high energy heavy ion
collisions were emitted at freeze-out from an equilibrium hadron gas. Our
considerations are based on an ideal gas at fixed temperature , baryon
number density , and vanishing total strangeness. The constituents of this
gas are all hadron resonances up to a mass of 2 GeV; they are taken to decay
according to the experimentally observed branching ratios. The ratios of the
various resulting hadron production rates are tabulated as functions of
and . These tables can be used for the equilibration analysis of any heavy
ion data; we illustrate this for some specific cases.Comment: 12 pages (not included :13 figures + tables) report CERN-TH 6523/92
and Bielefeld preprint BI-TP 92/0
Coulomb Effect: A Possible Probe for the Evolution of Hadronic Matter
Electromagnetic field produced in high-energy heavy-ion collisions contains
much useful information, because the field can be directly related to the
motion of the matter in the whole stage of the reaction. One can divide the
total electromagnetic field into three parts, i.e., the contributions from the
incident nuclei, non-participating nucleons and charged fluid, the latter
consisting of strongly interacting hadrons or quarks. Parametrizing the
space-time evolution of the charged fluid based on hydrodynamic model, we study
the development of the electromagnetic field which accompanies the high-energy
heavy-ion collisions. We found that the incident nuclei bring a rather strong
electromagnetic field to the interaction region of hadrons or quarks over a few
fm after the collision. On the other hand, the observed charged hadrons'
spectra are mostly affected (Coulomb effect) by the field of the charged fluid.
We compare the result of our model with experimental data and found that the
model reproduces them well. The pion yield ratio pi^-/pi+ at a RHIC energy,
Au+Au 100+100 GeV/nucleon, is also predicted.Comment: 23 pages, RevTex, 19 eps figures, revised versio
Unlike particle correlations and the strange quark matter distillation process
We present a new technique for observing the strange quark matter
distillation process based on unlike particle correlations. A simulation is
presented based on the scenario of a two-phase thermodynamical evolution model.Comment: 15 pages, 2 figures, 1 tabl
Resonance Model of for Kaon Production in Heavy Ion Collisions
The elementary production cross sections
and are needed to describe
kaon production in heavy ion collisions. The reactions
were studied previously by a resonance model. The model can explain the
experimental data quite well \cite{tsu}. In this article, the total cross
sections at intermediate energies (from the kaon
production threshold to3 GeV of center-of-mass energy) are
calculated for the first time using the same resonance model. The resonances,
and for the reactions, and
, and for the reactions are taken into account coherently as
the intermediate states in the calculations. Also t-channel vector meson exchange is included. The results show that
exchange is neglegible for the
reactions, whereas this meson does not contribute to the reactions. Furthemore, the
contributions to kaon production in heavy ion collisions are not only
non-neglegible but also very different from the
reactions. An argument valid for cannot be extended to
reactions. Therefore, cross sections for including correctly the different isospins must beComment: ( Replaced with corrections of printing errors in the Table. ) 15
pages, Latex file with 4 figures, 1 figure is included in the text. A
compressed uuencode file for 3 figures is appended. (A figure file format was
changed.) Also available upon reques
Tetrazine- and trans-cyclooctene-functionalised polypept(o)ides for fast bioorthogonal tetrazine ligation
The inverse electron demand Diets-Alder (IEDDA) reaction-initiated ligation between 1,2,4,5-tetra-zines (Tz) and trans-cyclooctenes (TCO) is one of the fastest bioorthogonal reactions known today and is therefore increasingly used for in vivo click chemistry. Described herein is the synthesis of Tz- and TCO-functionalised polypeptides, polypeptoids and polypeptide-block-polypeptoids (polypept(o) ides) by ring-opening polymerisation of the corresponding N-carboxyanhydrides using Tz- or TCO-functional amine initiators. Despite the reactivity of tetrazines, polymers with low dispersity and high end group integrity can be obtained as observed by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) spectroscopy and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Amphiphilic Tz-functionalised block copolypept(o)ides were used to prepare polymeric micelles and organic colloids by miniemulsion techniques, which may find an application as clearing agents in pretargeted nuclear imaging and therapy using efficient in vivo click chemistry. The reaction kinetics of the tetrazine ligation using the synthesised polymers and the accessibility of the Tz groups on the polymeric nanoparticles were evaluated using UV Vis and fluorescence correlation spectroscopy (FCS), and second-order rate constants were determined by stopped-flow spectrophotometry ensuring quantitative conversions in seconds at sub-millimolar concentrations (10-30 s).Drug Delivery Technolog
Bose-Einstein Correlations of Pion Wavepackets
A wavepacket model for a system of free pions, which takes into account the
full permutation symmetry of the wavefunction and which is suitable for any
phase space parametrization is developed. The properties of the resulting mixed
ensembles and the two-particle correlation function are discussed. A physical
interpretation of the chaoticity lambda as localizat of the pions in the source
is presented.
Two techniques to generate test-particles, which satisfy the probability
densities of the wavepacket state, are studied:
1. A Monte Carlo procedure in momentum space based on the standard Metropolis
technique.
2. A molecular dynamic procedure using Bohm's quantum theory of motion.
In order to reduce the numerical complexity, the separation of the
wavefunction into momentum space clusters is discussed. In this context th
influence of an unauthorized factorization of the state, i. e. the omissio of
interference terms, is investigated. It is shown that the correlation radius
remains almost uneffected, but the chaoticity parameter decreases
substantially. A similar effect is observed in systems with high multiplic
where the omission of higher order corrections in the analysis of two-part
correlations causes a reduction of the chaoticity and the radius.
The approximative treatment of the Coulomb interaction between pions and
source is investigated. The results suggest that Coulomb effects on the co
radii are not symmetric for pion pairs of different charges. For negative the
radius, integrated over the whole momentum spectrum, increases substan while
for positive pions the radius remains almost unchanged.Comment: 15 pages, 8 figures, 0.8 Mb, uses ljour2-macro, Submitted to Z. Phys.
A (1997
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