881 research outputs found
Phase-space density in heavy-ion collisions revisited
We derive the phase space density of bosons from a general boson
interferometry formula.
We find that the phase space density is connected with the two-particles and
the single particle density distribution functions. If the boson density is
large, the two particles density distribution function can not be expressed as
a product of two single particle density distributions. However, if the boson
density is so small that two particles density distribution function can be
expressed as a product of two single particle density distributions, then
Bertsch's formula is recovered. For a Gaussian model, the effects of
multi-particles Bose-Einstein correlations on the mean phase space density are
studied.Comment: 18 Pages, Four eps files, EPJC in Pres
On kinematics and dynamics of independent pion emission
Multiparticle boson states, proposed recently for 'independently' emitted
pions in heavy ion collisions, are reconsidered in standard second quantized
formalism and shown to emerge from a simplistic chaotic current dynamics.
Compact equations relate the density operator, the generating functional of
multiparticle counts, and the correlator of the external current to each other.
'Bose-Einstein-condensation' is related to the external pulse. A quantum master
equation is advocated for future Monte-Carlo simulations.Comment: 10 pages LaTeX, Sec.7 adde
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
Hbt Analysis of Anisotropic Transverse Flow
The effects of anisotropic transverse collective flow on the HBT correlation
function is studied. There exist three different physics contributions related
to flow which affect the correlation function: anisotropic source shape,
anisotropic space-momentum correlations in pion emission, and the effects
related to the HBT measurement of the size of a moving source in different
reference frames. Resolution of these contributions experimentally can lead to
a detailed understanding of both collective flow in nucleus-nucleus collisions
and the HBT technique itself. A method is presented which permits the
derivation of model independent relations between the radius of a source
measured in a frame in which it is moving and in its rest frame.Comment: latex, 16 pages, 1 figur
Evidence for chemical equilibration at RHIC
This contribution focuses on the results of statistical model calculations at
RHIC energies, including recently available experimental data. Previous
calculations of particle yield ratios showed good agreement with measurements
at SPS and lower energies, suggesting that the composite system possesses a
high degree of chemical equilibrium at freeze-out. The effect of feeddown
contamination on the model parameters is discussed, and the sensitivity of
individual ratios to the model parameters (, ) is illustrated.Comment: Talk presented at Strange Quarks in Matter 2001, Frankfurt, September
24-29, 2001. Proceedings to be published by J. Phys. G. 8 pages with 4
figure
Multi-boson effects and the normalization of the two-pion correlation function
The two-pion correlation function can be defined as a ratio of either the
measured momentum distributions or the normalized momentum space probabilities.
We show that the first alternative avoids certain ambiguities since then the
normalization of the two-pion correlator contains important information on the
multiplicity distribution of the event ensemble which is lost in the second
alternative. We illustrate this explicitly for specific classes of event
ensembles.Comment: 6 pages, three figures,submit to PR
Bioactivity of volatile organic compounds by Aureobasidium species against gray mold of tomato and table grape
Aureobasidium strains isolated from diverse unconventional environments belonging to the species A. pullulans, A. melanogenum, and A. subglaciale were evaluated for Volatile Organic Compounds (VOCs) production as a part of their modes of action against Botrytis cinerea of tomato and table grape. By in vitro assay, VOCs generated by the antagonists belonging to the species A. subglaciale showed the highest inhibition percentage of the pathogen mycelial growth (65.4%). In vivo tests were conducted with tomatoes and grapes artificially inoculated with B. cinerea conidial suspension, and exposed to VOCs emitted by the most efficient antagonists of each species (AP1, AM10, AS14) showing that VOCs of AP1 (A. pullulans) reduced the incidence by 67%, partially confirmed by the in vitro results. Conversely, on table grape, VOCs produced by all the strains did not control the fungal incidence but were only reducing the infection severity (< 44.4% by A. pullulans; < 30.5% by A. melanogenum, and A. subglaciale). Solid-phase microextraction (SPME) and subsequent gas chromatography coupled to mass spectrometry identified ethanol, 3-methyl-1-butanol, 2-methyl-1-propanol as the most produced VOCs. However, there were differences in the amounts of produced VOCs as well as in their repertoire. The EC50 values of VOCs for reduction of mycelial growth of B. cinerea uncovered 3-methyl-1-butanol as the most effective compound. The study demonstrated that the production and the efficacy of VOCs by Aureobasidium could be directly related to the specific species and pathosystem and uncovers new possibilities for searching more efficient VOCs producing strains in unconventional habitats other than plant
Analytic Solution of the Pion-Laser Model
Brooding over bosons, wave packets and Bose - Einstein correlations, we find
that a generalization of the pion-laser model for the case of overlapping
wave-packets is analytically solvable with complete n-particle symmetrization.
The effective radius parameter of the two-particle correlation function is
reduced for low values and enlargened for high values of the mean momentum in
the rare gas limiting case, as compared to the case when multi-particle
symmetrization effects are neglected.
These results explicitly depend on the multiplicity, providing a theoretical
basis for event-by-event analysis of high energy heavy ion reactions.Comment: LaTeX, ReVTeX 3.1, 7 pages, uses 1 eps figure and epsfig.sty
(shortened version
Hanbury-Brown--Twiss Analysis in a Solvable Model
The analysis of meson correlations by Hanbury-Brown--Twiss interferometry is
tested with a simple model of meson production by resonance decay. We derive
conditions which should be satisfied in order to relate the measured momentum
correlation to the classical source size. The Bose correlation effects are
apparent in both the ratio of meson pairs to singles and in the ratio of like
to unlike pairs. With our parameter values, we find that the single particle
distribution is too distorted by the correlation to allow a straightforward
analysis using pair correlation normalized by the singles rates. An analysis
comparing symmetrized to unsymmetrized pairs is more robust, but nonclassical
off-shell effects are important at realistic temperatures.Comment: 21 pages + 9 figures (tarred etc. using uufiles, submitted
separately), REVTeX 3.0, preprint number: DOE/ER/40561-112/INT93-00-3
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