71,248 research outputs found

### Vector-to-Pseudoscalar and Meson-to-Baryon Ratios in Hadronic Z Decays at LEP

Mass dependences of the total production rates per hadronic Z decay of all
light-flavour hadrons measured so far at LEP are extrapolated to the zero mass
limit (m=0) using phenomenological laws of hadron production related to the
spin, isospin, strangeness content and mass of the particles. The
vector-to-pseudoscalar and meson-to-baryon ratios at m=0 are found to be: rho^+
/ 3 pi^+ = 1.2 +/- 0.3 and pi^+ / p = 2.9 +/- 0.3, in good agreement with the
predictions of quark combinatorics.Comment: LaTeX with sprocl.sty; 6 pages with 2 eps-figures; minor Editor's
corrections. Talk given at the 30th International Symposium on Multiparticle
Dynamics, Tihany, Lake Balaton, Hungary, October 9-15, 2000. To be published
in the Proceedings (World Scientific, Singapore

### (Non)Thermal Aspects of Charmonium Production and a New Look at J/$\psi$ Suppression

To investigate a recent proposal that J/$\psi$ production in
ultra-relativistic nuclear collisions is of thermal origin we have reanalyzed
the data from the NA38/50 collaboration within a thermal model including charm.
Comparison of the calculated with measured yields demonstrates the non-thermal
origin of hidden charm production at SPS energy. However, the ratio
$\psi^{'}$/(J/$\psi)$ exhibits, in central nucleus-nucleus collisions, thermal
features which lead us to a new interpretation of open charm and charmonium
production at SPS energy. Implications for RHIC and LHC energy measurements
will be discussed.Comment: 12 pages, 3 eps figures, final version with slight corrections, Phys.
Lett. B (in print

### Statistical hadronization of charmed quarks at SPS and RHIC

Production of open and hidden charm hadrons in heavy ion collisions is
considered within the statistical coalescence model. The charmed
quark-antiquark pairs are assumed to be created at the initial stage of the
reaction in hard parton collisions. The number of these pairs is conserved
during the evolution of the system. At the hadronization stage, the charmed
(anti)quarks are distributed among open and hidden charm hadrons in accordance
with the laws of statistical mechanics.
The model is in agreement with the experimental data on J/psi to Drell-Yan
ratio in Pb+Pb collisions at SPS. This agreement can be reached only if a
rather strong enhancement of the open charm production in central Pb+Pb
collisions is assumed. A possible mechanism of the charm enhancement is
discussed.
At the top RHIC energy, the model predicts an increase of J/psi to Drell-Yan
ratio in more central nucleus-nucleus collisions with respect to less central
ones.Comment: Presented at 16th International Conference "Quark Matter", Nantes
(France), July 18-24, 2002; 4 pages, LaTeX, 2 PS-figure

### Extended Modified Observable Technique for a Multi-Parametric Trilinear Gauge Coupling Estimation at LEP II

This paper describes the extension of the Modified Observables technique in
estimating simultaneously more than one Trilinear Gauge Couplings. The optimal
properties, unbiasedness and consistent error estimation of this method are
demonstrated by Monte Carlo experimentation using $\ell \nu jj$ four-fermion
final state topologies. Emphasis is given in the determination of the expected
sensitivities in estimating the $\lambda_{\gamma} - \Delta g_{1}^{z}$ and
$\Delta k_{\gamma} - \Delta g_{1}^{z}$ pair of couplings with data from the 183
GeV LEPII run.Comment: (17 pages, 8 figures

### Multidimensional Binning Techniques for a Two Parameter Trilinear Gauge Coupling Estimation at LEP II

This paper describes two generalization schemes of the Optimal Variables
technique in estimating simultaneously two Trilinear Gauge Couplings. The first
is an iterative procedure to perform a 2-dimensional fit using the linear terms
of the expansion of the probability density function with respect to the
corresponding couplings, whilst the second is a clustering method of
probability distribution representation in five dimensions. The pair production
of W's at 183 GeV center of mass energy, where one W decays leptonically and
the other hadronically, was used to demonstrate the optimal properties of the
proposed estimation techniques.Comment: (25 pages, 11 figures

### Using a Logic Programming Framework to Control Database Query Dialogues in Natural Language

We present a natural language question/answering system to interface the University of Évora databases that uses clarification dialogs in order to clarify user questions. It was developed in an integrated logic programming framework, based on constraint logic programming using the GnuProlog(-cx) language [2,11] and the ISCO framework [1]. The use of this LP framework allows the integration of Prolog-like inference mechanisms with classes and inheritance, constraint solving algorithms and provides the connection with relational databases, such as PostgreSQL. This system focus on the questions’ pragmatic analysis, to handle ambiguity, and on an efficient dialogue mechanism, which is able to place relevant questions to clarify the user intentions in a straightforward manner. Proper Nouns resolution and the pp-attachment problem are also handled.
This paper briefly presents this innovative system focusing on its ability to correctly determine the user intention through its dialogue capability

### Multiplicities, fluctuations and correlations

The recent results on hadron multiplicities in heavy and light quark
fragmentation, multiplicity local fluctuations and multiparticle correlations
submitted to the Conference are reviewed.Comment: 5 pages, 4 eps figs. Talk given at the 31st International Conference
on High Energy Physics (ICHEP02), Amsterdam, The Netherlands, 24-31 July
2002. To appear in the Proceeding

### Kahler geometry of toric varieties and extremal metrics

Recently Guillemin gave an explicit combinatorial way of constructing "toric"
Kahler metrics on (symplectic) toric varieties, using only data on the moment
polytope. In this paper, differential geometric properties of these metrics are
investigated using Guillemin's construction. In particular, a nice
combinatorial formula for the scalar curvature is given, and the Euler-Lagrange
condition for such "toric" metrics being extremal (in the sense of Calabi) is
derived. A construction, due to Calabi, of a 1-parameter family of extremal
metrics of non-constant scalar curvature is recast very simply and explicitly.
Finally, a curious combinatorial formula for convex polytopes, that follows
from the relation between the total integral of the scalar curvature and the
wedge product of the first Chern class with a suitable power of the Kahler
class, is presented.Comment: 12 pages, submitted to International Journal of Mathematic

### Dual projection in a two-dimensional curved expanding universe

It is a well known result that the scalar field is composed of two chiral
particles (Floreanini-Jackiw particles) of opposite chiralities. Also, that a
Siegel particle spectrum is formed by a nonmover field (a Hull's noton) and a
FJ particle. In this work we show that in a scalar field spectrum, in a curved
expanding universe scenario, we can find two dynamical chiral fields.Comment: 6 pages, Revtex. Final version to appear in Int. J. Mod. Phys.

### Toric Kahler Metrics: Cohomogeneity One Examples of Constant Scalar Curvature in Action-Angle Coordinates

In these notes, after an introduction to toric Kahler geometry, we present
Calabi's family of U(n)-invariant extremal Kahler metrics in symplectic
action-angle coordinates and show that it actually contains, as particular
cases, many interesting cohomogeneity one examples of constant scalar
curvature.Comment: 20 pages, 1 figure, for the proceedings of the XI International
Conference on Geometry, Integrability and Quantization, Varna, Bulgaria, June
5--10, 200

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