785 research outputs found
Phasespace Correlations of Antideuterons in Heavy Ion Collisions
In the framework of the relativistic quantum molecular dynamics approach
({\small RQMD}) we investigate antideuteron () observables in
Au+Au collisions at 10.7~AGeV. The impact parameter dependence of the formation
ratios and is calculated. In central
collisions, the antideuteron formation ratio is predicted to be two orders of
magnitude lower than the deuteron formation ratio. The yield in
central Au+Au collisions is one order of magnitude lower than in Si+Al
collisions. In semicentral collisions different configuration space
distributions of 's and 's lead to a large
``squeeze--out'' effect for antideuterons, which is not predicted for the
's
A stopped Delta-Matter Source in Heavy Ion Collisions at 10 GeV/n
We predict the formation of highly dense baryon-rich resonance matter in
Au+Au collisions at AGS energies. The final pion yields show observable signs
for resonance matter. The Delta(1232) resonance is predicted to be the dominant
source for pions of small transverse momenta. Rescattering effects --
consecutive excitation and deexcitation of Deltas -- lead to a long apparent
lifetime (> 10 fm/c) and rather large volumina (several 100 fm^3) of the
Delta-matter state. Heavier baryon resonances prove to be crucial for reaction
dynamics and particle production at AGS.Comment: 17 pages, 5 postscript figures, uses psfig.sty and revtex.st
Reconstruction of the Proton Source in Relativistic Heavy Ion Collisions
We describe a direct method to reconstruct the transverse proton source formed in a relativistic heavy ion collision, making use of experimentally measured proton and deuteron spectra and assuming that deuterons are formed via two-nucleon coalescence. We show that an ambiguity with respect to the source temperature still persists and we indicate a possible solution to the problem
Dibaryons with Strangeness: their Weak Nonleptonic Decay using SU(3) Symmetry and how to find them in Relativistic Heavy-Ion Collisions
Weak SU(3) symmetry is successfully applied to the weak hadronic decay
amplitudes of octet hyperons. Weak nonmesonic and mesonic decays of various
dibaryons with strangeness, their dominant decay modes, and lifetimes are
calculated. Production estimates for BNL's Relativistic Heavy-Ion Collider are
presented employing wave function coalescence. Signals for detecting strange
dibaryon states in heavy-ion collisions and revealing information about the
unknown hyperon-hyperon interactions are outlined.Comment: 4 pages, 2 figures, uses RevTeX, discussion about the model of the
weak decay and experimental signals extended, references update
Transcriptional profile of maize roots under acid soil growth
Aluminum (Al) toxicity is one of the most important yield-limiting factors of many crops worldwide. The primary symptom of Al toxicity syndrome is the inhibition of root growth leading to poor water and nutrient absorption. Al tolerance has been extensively studied using hydroponic experiments. However, unlike soil conditions, this method does not address all of the components that are necessary for proper root growth and development. In the present study, we grew two maize genotypes with contrasting tolerance to Al in soil containing toxic levels of Al and then compared their transcriptomic responses
Properties of Exotic Matter for Heavy Ion Searches
We examine the properties of both forms of strange matter, small lumps of
strange quark matter (strangelets) and of strange hadronic matter (Metastable
Exotic Multihypernuclear Objects: MEMOs) and their relevance for present and
future heavy ion searches. The strong and weak decays are discussed separately
to distinguish between long-lived and short-lived candidates where the former
ones are detectable in present heavy ion experiments while the latter ones in
future heavy ion experiments, respectively. We find some long-lived strangelet
candidates which are highly negatively charged with a mass to charge ratio like
a anti deuteron (M/Z=-2) but masses of A=10 to 16. We predict also many
short-lived candidates, both in quark and in hadronic form, which can be highly
charged. Purely hyperonic nuclei are bound and have a negative charge while
carrying a positive baryon number. We demonstrate also that multiply charmed
exotics (charmlets) might be bound and can be produced at future heavy ion
colliders.Comment: 10 pages, 4 figures, uses IOP style and epsf.sty, to be published in
Journal of Physics, Proceedings of the International Symposium on Strangeness
in Quark Matter 1997, April 14-18, Thera (Santorini), Hellas. Corrected
typos, added comment about bag constant
A series of new conjugated oligothiophenes for organic electronics
Thiophene oligomers and polymers can be found in a huge number of materials with applications in the field of Organic Electronics. Chemical and electrochemical syntheses along with electrochemical studies and complete characterization of a series of new conjugated oligothiophene derivatives are reported. Two different molecular architectures, D-A (donor-acceptor) and A-D-A (acceptor-donor-acceptor), were taken into account. The results from voltammetric experiments and optical studies confirm the close relationship between the structure of these compounds and their electrochemical behaviour. This series of oligothiophenes shows low bandgaps, a mandatory requirement for their use in Organic Electronics, and, clearly, they are promising candidates for future synthetic studies in order to modify their optical and electrochemical properties to achieve better performances as organic semiconductors
QCD equation of state in a virial expansion
We describe recent three-flavor QCD lattice data for the pressure, speed of
soun d and interaction measure at nonzero temperature and vanishing chemical
potentia l within a virial expansion. For the deconfined phase we use a
phenomenological model which includes non-pert urbative effects from dimension
two gluon condensates that reproduce the free en ergy of quenched QCD very
well. The hadronic phase is parameterized by a generalized resonance-gas model.
Furthermore, we extend this approach to finite quark densities introducing an
ex plicit -dependence of the interaction. We calculate pressure,
quark-number density, entropy and energy density and compare to results of
lattice calculatio ns. We, additionally, investigate the structure of the phase
diagram by calculating the isobaric and isentropic lines as well as the
critical endpoint in the ()-plane.Comment: 9 pages, 11 figures. Submitted to Phys. Rev.
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