205 research outputs found
Particle yield fluctuations and chemical non-equilibrium at RHIC
We study charge fluctuations within the statistical hadronization model.
Considering both the particle yield ratios and the charge fluctuations we show
that it is possible to differentiate between chemical equilibrium and
non-equilibrium freeze-out conditions. As an example of the procedure we show
quantitatively how the relative yield ratio together with the
normalized net charge fluctuation v(Q)=\ave{\Delta Q^2}/\ave{\Nch} constrain
the chemical conditions at freeze-out. We also discuss the influence of the
limited detector acceptance on fluctuation measurements, and show how this can
be accounted for within a quantitative analysis.Comment: Accepted for publication by Physical Review
Resonances and fluctuations at SPS and RHIC
We perform an analysis of preliminary data on hadron yields and fluctuations
within the Statistical hadronization ansatz. We describe the theoretical
disagreements between different statistical models currently on the market, and
show how the simultaneous analysis of yields and fluctuations can be used to
determine if one of them can be connected to underlying physics. We perform
such an analysis on preliminary RHIC and SPS A-A data that includes particle
yields, ratios and event by event fluctuations. We show that the equilibrium
statistical model can not describe the fluctuation measured at RHIC and
SPS, unless an unrealistically small volume is assumed. Such small volume then
makes it impossible to describe the total particle multiplicity. The
non-equilibrium model,on the other hand, describes both the fluctuation
and yields acceptably due to the extra boost to the fluctuation provided
by the high pion chemical potential. We show, however, that both models
significantly over-estimate the fluctuation measured at the SPS, and
speculate for the reason behind this.Comment: Presented at Hot Quarks, 2006 In press, European Physical Journal
An operational information systems architecture for assessing sustainable transportation planning: Principles and design
This paper offers the description of an integrated information system framework for the assessment of transportation planning and management. After an introductory exposition, in the first part of the paper, a broad overview of international experiences regarding information systems on transportation is given, focusing in particular on the relationship between transportation system's performance monitoring and the decision-making process, and on the importance of this connection in the evaluation and planning process, in Italian and European cases. Next, the methodological design of an information system to support efficient and sustainable transportation planning and management aiming to integrate inputs from several different data sources is presented. The resulting framework deploys modular and integrated databases which include data stemming from different national or regional data banks and which integrate information belonging to different transportation fields. For this reason, it allows public administrations to account for many strategic elements that influence their decisions regarding transportation, both from a systemic and infrastructural point of view
Strange Hadron Resonances and QGP Freeze-out
We describe how the abundance and distribution of hyperon resonances can be
used to probe freeze-out conditions. We demonstrate that resonance yields allow
us to measure the time scales of chemical and thermal freeze-outs. This should
permit a direct differentiation between the explosive sudden, and staged
adiabatic freeze-out scenarios.Comment: 8 pages including 4 figures, in Proceedings of Strange Quark Matter
2001, Frankfurt, submitted to J. Phys. G version 2: refernces
corrected/added, numercial corrections in figures 2,3,
Forward-backward correlations in nucleus-nucleus collisions: baseline contributions from geometrical fluctuations
We discuss the effects of initial collision geometry and centrality bin
definition on correlation and fluctuation observables in nucleus-nucleus
collisions. We focus on the forward-backward correlation coefficient recently
measured by the STAR Collaboration in Au+Au collisions at RHIC. Our study is
carried out within two models: the Glauber Monte Carlo code with a `toy'
wounded nucleon model and the hadron-string dynamics (HSD) transport approach.
We show that strong correlations can arise due to averaging over events in one
centrality bin. We, furthermore, argue that a study of the dependence of
correlations on the centrality bin definition as well as the bin size may
distinguish between these `trivial' correlations and correlations arising from
`new physics'.Comment: 12 pages, 6 figure
Specific Microbial Communities Are Selected in Minimally-Processed Fruit and Vegetables according to the Type of Product
Fruits and vegetables (F&V) products are recommended for the daily diet due to their low caloric content, high amount of vitamins, minerals and fiber. Furthermore, these foods are a source of various phytochemical compounds, such as polyphenols, flavonoids and sterols, exerting antioxidant activity. Despite the benefits derived from eating raw F&V, the quality and safety of these products may represent a source of concern, since they can be quickly spoiled and have a very short shelf-life. Moreover, they may be a vehicle of pathogenic microorganisms. This study aims to evaluate the bacterial and fungal populations in F&V products (i.e., iceberg lettuces, arugula, spinaches, fennels, tomatoes and pears) by using culture-dependent microbiological analysis and high-throughput sequencing (HTS), in order to decipher the microbial populations that characterize minimally-processed F&V. Our results show that F&V harbor diverse and product-specific bacterial and fungal communities, with vegetables leaf morphology and type of edible fraction of fruits exerting the highest influence. In addition, we observed that several alterative (e.g., Pseudomonas and Aspergillus) and potentially pathogenic taxa (such as Staphylococcus and Cladosporium) are present, thus emphasizing the need for novel product-specific strategies to control the microbial composition of F&V and extend their shelf-life
Statistical hadronization phenomenology in fluctuations at ultra-relativistic energies
We discuss the information that can be obtained from an analysis of
fluctuations in heavy ion collisions within the context of the statistical
model of particle production. We then examine the recently published
experimental data on ratio fluctuations, and use it to obtain constraints on
the statistical properties (physically relevant ensemble, degree of chemical
equilibration, scaling across energies and system sizes) and freeze-out
dynamics (amount of reinteraction between chemical and thermal freeze-out) of
the system.Comment: Proceedings, SQM2009. Fig. 4, the main results figure, was wrong due
to editing mistake, now correcte
A comparison of statistical hadronization models
We investigate the sensitivity of fits of hadron spectra produced in heavy
ion collisions to the choice of statistical hadronization model. We start by
giving an overview of statistical model ambiguities, and what they tell us
about freeze-out dynamics. We then use Montecarlo generated data to determine
sensitivity to model choice. We fit the statistical hadronization models under
consideration to RHIC data, and find that a comparison fits can shed
light on some presently contentious questions.Comment: Proceedings for SQM2003 [7th Int. Conf. on Strangeness in Quark
Matter (Atlantic Beach, NC, USA, Mar 12-17, 2003)], to be published in
Journal of Physics G (Typos corrected, reference added
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