311 research outputs found
Forest hydrology and watershed management = hydrologie forestiÚre et aménagement des bassins hydrologiques
On compare les Ă©coulements d'une parcelle (400 mÂČ), de bassins-versants Ă©lĂ©mentaires (environ (1.5 ha) et d'un petit bassin-versant (4.5 kmÂČ) situĂ©s sur le mĂȘme substratum gĂ©ologique, en forĂȘt tropicale humide. Le ruissellement annuel de la parcelle est de 8.8 % et celui du petit bassin de 23 % (1981), diffĂ©rence s'expliquant par l'analyse des systĂšmes pĂ©dologiques. Les Ă©coulements des bassins Ă©lĂ©mentaires peuvent ĂȘtre semblables Ă ceux de la parcelle ou du petit bassin, selon le stade d'Ă©volution de leur couverture pĂ©dologique. (RĂ©sumĂ© d'auteur
L'opération ECEREX : études sur la mise en valeur de l'écosystÚme forestier guyanais aprÚs déboisement : le point sur les recherches en cours
Nuclear energy density functional from chiral pion-nucleon dynamics: Isovector spin-orbit terms
We extend a recent calculation of the nuclear energy density functional in
the systematic framework of chiral perturbation theory by computing the
isovector spin-orbit terms: . The calculation
includes the one-pion exchange Fock diagram and the iterated one-pion exchange
Hartree and Fock diagrams. From these few leading order contributions in the
small momentum expansion one obtains already a good equation of state of
isospin-symmetric nuclear matter. We find that the parameterfree results for
the (density-dependent) strength functions and agree
fairly well with that of phenomenological Skyrme forces for densities . At very low densities a strong variation of the strength functions
and with density sets in. This has to do with chiral
singularities and the presence of two competing small mass scales
and . The novel density dependencies of and
as predicted by our parameterfree (leading order) calculation should
be examined in nuclear structure calculations.Comment: 9 pages, 3 figure, published in: Physical Review C68, 014323 (2003
The USCT reference database
Ultrasound Computer Tomography (USCT) is an emerging technology mostly aimed at breast cancer imaging. Following the idea of open science a USCT reference database is established with open and easy to use data and code interfaces. The aim is to promote and facilitate the exchange of available reconstruction algorithms and raw data sets from different USCT devices throughout the growing USCT community. Additionally, the feedback about data and system architecture of the scientists working on reconstruction methods will be published online to help to drive further development of the various measurement setups
Systematic study of the pp -> pp omega reaction
A systematic study of the production of omega-mesons in
proton-proton-collisions was carried out in a kinematically complete experiment
at three excess energies(epsilon= 92, 128, 173MeV). Both protons were detected
using the large-acceptance COSY-TOF spectrometer at an external beam line at
the Cooler Synchrotron COSY at Forschungszentrum J\"ulich. The total cross
section, angular distributions of both omega-mesons and protons were measured
and presented in various reference frames such as the overall CMS, helicity and
Jackson frame. In addition, the orientation of the omega-spin and invariant
mass spectra were determined. We observe omega-production to take place
dominantly in Ss and Sp final states at epsilon = 92, 128 MeV and,
additionally, in Sd at epsilon= 173 MeV. No obvious indication of resonant
omega-production via N^*-resonances was found, as proton angular distributions
are almost isotropic and invariant mass spectra are compatible with phase space
distributions. A dominant role of ^3P_1 and ^1S_0 initial partial waves for
omega-production was concluded from the orientation of the decay plane of the
omega-meson. Although the Jackson angle distributions in the omega-p-Jackson
frame are anisotropic we argue that this is not an indication of a resonance
but rather a kinematical effect reflecting the anisotropy of the omega angular
distribution. The helicity angle distribution in the omega-p-helicity frame
shows an anisotropy which probably reflects effects of the omega angular
momenta in the final state; this observable may be, in addition to the
orientation of the omega decay plane, the most sensitive one to judge the
validity of theoretical descriptions of the production process.Comment: 17 pages, 16 figures, accepted for publication in EPJ
Time-integrated luminosity recorded by the BABAR detector at the PEP-II e+e- collider
This article is the Preprint version of the final published artcile which can be accessed at the link below.We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the Ï(4S), Ï(3S), and Ï(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e-âe+e- and (for the Ï(4S) only) e+e-âÎŒ+ÎŒ- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross-sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross-sections of e+e-âe+e- and e+e-âÎŒ+ÎŒ-, the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross-sections. For data collected on the Ï(3S) and Ï(2S) resonances, an additional uncertainty arises due to Ïâe+e-X background. For data collected off the Ï resonances, we estimate an additional uncertainty due to time dependent efficiency variations, which can affect the short off-resonance runs. The relative uncertainties on the luminosities of the on-resonance (off-resonance) samples are 0.43% (0.43%) for the Ï(4S), 0.58% (0.72%) for the Ï(3S), and 0.68% (0.88%) for the Ï(2S).This work is supported by the US Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat Ă lâEnergie Atomique and Institut National de Physique NuclĂ©aire et de Physiquedes Particules (France), the Bundesministerium fĂŒr Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Ciencia e InnovaciĂłn (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A.P. Sloan Foundation (USA)
Track Finding Efficiency in BaBar
We describe several studies to measure the charged track reconstruction
efficiency and asymmetry of the BaBar detector. The first two studies measure
the tracking efficiency of a charged particle using and initial state
radiation decays. The third uses the decays to study the asymmetry in
tracking, the fourth measures the tracking efficiency for low momentum tracks,
and the last measures the reconstruction efficiency of particles. The
first section also examines the stability of the measurements vs BaBar running
periods.Comment: 20 pages, 30 figures, Submitted to Nuclear Instruments and Methods in
Physics Research
The pK0\Sigma+ final state in proton-proton collisions
This paper reports results from a study of the reaction pp->pK0\Sigma+ at
beam momenta of p_{beam} = 2950, 3059, and 3200 MeV/c (excess energies of
\epsilon= 126, 161, and 206 MeV). Total cross sections were determined for all
energies; a set of differential cross sections (Dalitz plots; invariant mass
spectra of all two-body subsystems; angular distributions of all final state
particles; distributions in helicity and Jackson frames) are presented for
\epsilon= 161 MeV. The total cross sections are proportional to the volume of
available three-body phase-space indicating that the transition matrix element
does not change significantly in this range of excess energies. It is concluded
from the differential data that the reaction proceeds dominantly via the
N(1710)P_{11} and/or N(1720)P_{13} resonance(s); N(1650)S_{11} and
\Delta(1600)P_{33} could also contribute.Comment: 15 pages, 10 figure
Diffuse scattering
Diffuse neutron scattering covers a wide range of phenomena related to short range nuclear and magnetic orderings. Although it is âa prioriâ simple to measure, the underlying physics is often quite complex. Extracting useful and reliable information requires careful corrections and calibrations, and appropriate models of analysis, specifics for each physical case. This paper yields a partial and subjective glance on this specific subject, showing studies about chemical orderings in binary alloys and magnetic correlations in frustrated âspin icesâ as examples
Observation of the baryonic decay B \uaf 0 \u2192 \u39bc+ p \uaf K-K+
We report the observation of the baryonic decay B\uaf0\u2192\u39bc+p\uafK-K+ using a data sample of 471
7106 BB\uaf pairs produced in e+e- annihilations at s=10.58GeV. This data sample was recorded with the BABAR detector at the PEP-II storage ring at SLAC. We find B(B\uaf0\u2192\u39bc+p\uafK-K+)=(2.5\ub10.4(stat)\ub10.2(syst)\ub10.6B(\u39bc+))
710-5, where the uncertainties are statistical, systematic, and due to the uncertainty of the \u39bc+\u2192pK-\u3c0+ branching fraction, respectively. The result has a significance corresponding to 5.0 standard deviations, including all uncertainties. For the resonant decay B\uaf0\u2192\u39bc+p\uaf\u3c6, we determine the upper limit B(B\uaf0\u2192\u39bc+p\uaf\u3c6)<1.2
710-5 at 90% confidence level
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