EDP Sciences OAI-PMH repository (1.2.0)

    Upper limits on resonance contributions to proton-proton elastic scattering in the c.m. mass range 2.05-2.85 GeV/ c

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    Recently published excitation functions in proton-proton (pp) elastic scattering observables in the laboratory energy range 0.5-2.5GeV provide an excellent data base to establish firm upper limits on the elasticities ηel = Γel/Γtot of possible isovector resonant contributions to the nucleon-nucleon (NN) system. Such contributions have been predicted to arise from dibaryonic states, with c.m. masses between 2.1-2.9GeV/c2, but have not been confirmed experimentally. A method to determine quantitatively the maximum value of ηel compatible with experimental data is presented. We use energy-dependent phase shift fits to the pp data base to model the non-resonant interaction. Based upon the differential cross-section data measured by the EDDA Collaboration an unbiased statistical test is constructed to obtain upper limits on ηel, that exclude larger values with a 99% confidence level. Results in the c.m. mass range 2.05-2.85GeV/c2 and total widths of 10-100MeV/c2 in the partial waves 1 S 0, 1 D 2, 3 P 0, 3 P 1, and 3 F 3 are presented and discussed

    Backward pion photoproduction

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    We present a systematic analysis of backward pion photoproduction for the reactions γ \gamma p \rightarrow π0 \pi^{0}_{} p and γ \gamma p \rightarrow π+ \pi^{+}_{} n . Regge phenomenology is applied at invariant collision energies above 3GeV in order to fix the reaction amplitude. A comparision with older data on π0 \pi^{0}_{} - and π+ \pi^{+}_{} -photoproduction at ϑ \vartheta = 180° indicates that the high-energy limit as given by the Regge calculation could be reached possibly at energies of around s \sqrt{{s}} ≃ 3 GeV. In the energy region of s \sqrt{{s}} \le2.5 GeV, covered by the new measurements of γ \gamma p \rightarrow π0 \pi^{0}_{} p differential cross-sections at large angles at ELSA, JLab, and LEPS, we see no clear signal for a convergence towards the Regge results. The baryon trajectories obtained in our analysis are in good agreement with those given by the spectrum of excited baryons

    Determination of the gluon polarization at RHIC and COMPASS

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    The most recent determinations of the gluon polarization in the nucleon, ΔGG {\frac{{\Delta G}}{{G}}} , obtained at RHIC and COMPASS experiments, are reviewed. The former accesses the gluon polarization mainly through the production of neutral pions (PHENIX) or jets (STAR) in polarized proton collisions. The latter uses the photon-gluon fusion in polarized lepton-nucleon scattering, tagged either by open charm or high-pT hadrons production. All the results are in good agreement, and favour values of ΔG roughly between 0 and 0.5 at a few (GeV/c)2 , thus in contradiction with what could be derived from the Ellis-Jaffe sum rule and the axial anomaly. Much stronger constraints will be obtained in a near future by both programs, helping us to clarify the role of gluons in the nucleon spin

    Determination of vector meson properties by matching resonance saturation to a constituent quark model

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    The properties of mesonic resonances can be calculated in terms of the low-energy coefficients of chiral perturbation theory (χ\chiPT) by extending unitarized χ\chiPT to higher energies. On the other hand, these low-energy coefficients can be calculated in two different models, namely i) by assuming resonance saturation and ii) within a constituent quark model. By matching the expressions of the two models combined with the results of unitarized χ\chiPT and the Weinberg sum rules, the properties of vector and axial-vector mesons can be calculated in the combined large-N c and chiral limit

    Orthogonal polynomial approach to calculate the two-nucleon transition operator in three dimensions

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    We give a short report on the possibility to use orthogonal polynomials (OP) in calculations that involve the two-nucleon (2N) transition operator. The presented work adds another approach to the set of previously developed methods (described in Phys. Rev. C 81, 034006 (2010); Few-Body Syst. 53, 237 (2012); K. Topolnicki, PhD thesis, Jagiellonian University (2014)) and is applied to the transition operator calculated at laboratory kinetic energy 300MeV. The new results for neutron-neutron and neutron-proton scattering observables converge to the results presented in Few-Body Syst. 53, 237 (2012) and to results obtained using the Arnoldi algorithm (Y. Saad, Iterative methods for sparse linear systems (SIAM Philadelphia, PA, USA 2003)). The numerical cost of the calculations performed using the new scheme is large and the new method can serve only as a backup to cross-check the previously used calculation schemes

    Structures of rotating traditional neutron stars and hyperon stars in the relativistic

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    The influence of rotation on the total masses and radii of neutron stars is calculated by Hartle’s slow-rotation formalism, while the equation of state is considered in a relativistic σ\sigma-ω\omega model. As the changes of the mass and radius of a real neutron star caused by rotation are very small in comparison with the total mass and radius, one can see that Hartle’s approximate method is rational to deal with the rotating neutron stars. If three property values, mass, radius and period, are observed for the same neutron star, then the EOS of this neutron star could be decided entirely

    Dynamics of polarization buildup by spin filtering

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    There has been much recent research into polarizing an antiproton beam, instigated by the recent proposal from the PAX (Polarized Antiproton eXperiment) project at GSI Darmstadt. It plans to polarize an antiproton beam by repeated interaction with a polarized internal target in a storage ring. The method of polarization by spin filtering requires many of the beam particles to remain within the ring after scattering off the polarized internal target via electromagnetic and hadronic interactions. We present and solve sets of differential equations which describe the buildup of polarization by spin filtering in many different scenarios of interest to projects planning to produce high-intensity polarized beams. These scenarios are: 1) spin filtering of a fully stored beam; 2) spin filtering while the beam is being accumulated, i.e. unpolarized particles are continuously being fed into the beam; 3) the particle input rate is equal to the rate at which particles are being lost due to scattering beyond the ring acceptance angle, the beam intensity remaining constant; 4) increasing the initial polarization of a stored beam by spin filtering; 5) the input of particles into the beam is stopped after a certain amount of time, but spin filtering continues. The rate of depolarization of a stored polarized beam on passing through an electron cooler is also shown to be negligible

    Éditorial

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    Evaluation de la qualité des eaux d'une rivière avec les protozoaires ciliés comme bioindicateurs de pollution. Comparaison avec la physico-chimie

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    Le but de notre étude était de connaître l'impact de la restructuration d'une station d'épuration sur la qualité des eaux de la Dore, grâce à l'utilisation des Protozoaires Ciliés comme indicateurs et à l'analyse physico-chimique des eaux. Pour la récolte du matériel biologique, un substrat artificiel (blocs de polyuréthane) a été utilisé permettant ainsi un échantillonnage standardisé. Après détermination des Ciliés et comptage des individus, l'application du système des saprobies, l'étude de la structure du peuplement (indices de diversité, diagrammes rang-fréquence) et analyse factorielle des correspondances permettent la mise en évidence de la qualité des eaux. Parallèlement une étude physico-chimique a été faite. 9 points du cours d'eau ont été suivis. L'étude montre une nette amélioration de la qualité des eaux au niveau de tous les points situés en aval du rejet de la station d'épuration par rapport à des études faites en 1985 et 1986 avant la restructuration de la station. Seules des pollutions organiques vraisemblablement d'origine domestique ont été enregistrées entre certaines stations. Les résultats des deux méthodes traités par l'A.F.C. (Analyse Factorielle des Correspondances) concordent sur l'ensemble de l'étude

    Application of habitat modelling in river rehabilitation and artificial habitat design

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    Over the last years there has been a growing interest in river rehabilitation and the design of artificial habitat funded by an increasing knowledge of the importance of physical habitat for populations of Atlantic salmon and trout. With the current developments in two- and three-dimensional computational hydraulics, a capability of predictive hydraulic modelling has been established and modelling and analysis of the artificial habitats are thereby possible as a part of the planning stage. This have been utilised in a project to integrate hydraulic modelling tools, habitat modelling tools, river editing tools and visualization tools into a system for analysis and design of river rehabilitation projects and artificial habitat construction. Current work includes development a river editing system where the user can edit the bathymetry of the river manually or automatically by inserting standardised habitat features like current deflectors or weirs, and a strengthening of the hydraulic and habitat models to include effects of winter temperatures and ice in the analysis. Early versions and prototypes of the system have been used in the design of artificial habitat for juvenile fish and in construction of migratory habitat for adult Atlantic salmon through weir basins
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