The isolation by distance model is both a population process and a surface model. In this model the surface is, on average, flat in every direction. By contrast, probably most observed genetic ...surfaces exhibit trends generated by complex long-distance populational processes. When one estimates the parameters of a Malécot-Morton equation for those surfaces, the isolation by distance model does not fit. In the simplest case, in first-order trends (two-dimensional clines) the genetic differentiation increases dramatically, faster per unit distance than it would by isolation by distance alone. When isolation by distance takes place but is hidden through the apparent and complicated relief of a surface, another surface model incorporating trend spatial analysis can bypass the difficulty of estimating the isolation by distance process if approached through the Malécot-Morton equation or through a measure of spatial autocorrelation.
The only recent eta' photoproduction data off proton available in literature are the differential and total cross sections published by the CLAS and CB-ELSA-TAPS Collaborations. However, the wide ...information about reaction cross sections are not sufficient to understand the role of resonances involved in the process. Different theoretical works stressed the importance to measure also polarization observables in order to solve the ambiguities in the choice of the parameters used in their models. We present the analysis of eta' photoproduction off the proton analysis, identifying the investigated meson by the pi+pi-eta, pi super(0)pi super(0)eta, and gamma gamma decay modes by using the GRAAL apparatus; and we show the preliminary GRAAL results on the beam asymmetry capital sigma at beam energy of 1475 MeV.
Differential and total cross section measurements on eta' photoproduction were published by the CLAS Collaboration (M. Dugger et al., Phys.Rev.Lett.96, 062001 (2006) and M. Williams et al., ...Phys.Rev.C80, 045213 (2009)) for center-of-mass energies from near the threshold up to 2.84 GeV, and by the CB-ELSA-TAPS Collaboration (V. Crede et al., Phys.Rev.C80, 055202 (2009)) up to 2.36 GeV and also making a precise threshold scan of the differential cross section in the 1446 - 1527.4 MeV gamma beam energy range. However, the wide information about reaction cross sections are not sufficient to understand the role of resonances involved in the process. Different theoretical works stressed the importance to have also polarization observables in order to solve the ambiguity in the choice of the parameters used in their models. We present the analysis of the eta' photoproduction off the proton, identifying the meson via the gamma gamma , pi super(0)pi super(0)eta, and pi super(+)pi super(-)eta decay modes by using the GRAAL apparatus; and we show the preliminary GRAAL results on the beam asymmetry capital sigma from the threshold (1.446 GeV) up to 1.5 GeV.
GRAAL: a polarized γ-ray beam at ESRF Bocquet, J.P.; Ajaka, J.; Anghinolfi, M. ...
Nuclear Physics A,
08/1997, Letnik:
622, Številka:
1-2
Journal Article, Conference Proceeding
Recenzirano
The GRAAL facility produces a highly polarized gamma-ray beam by Compton scattering of laser photons on the electrons of the European Synchrotron Radiation Facility (ESRF) at Grenoble. Preliminary ...results have been obtained with the LAGRANGE detector showing its excellent performances.
Neutron detection efficiency of BGO calorimeter at GRAAL Bartalini, O.; Bellini, V.; Bocquet, J.P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2006, Letnik:
562, Številka:
1
Journal Article
Recenzirano
Experimental results on the neutron detection efficiency of the GRAAL BGO calorimeter obtained from a study of
γ
p
→
π
+
n
reaction are reported. Pulse height spectra were measured for neutron ...energies from 80 to 650
MeV. A comparison of the experimental data with a GEANT-based simulation is presented.
New experimental approach to study meson photoproduction in nuclei is discussed. It is based on the measurement of the recoil nucleon as a tagger for identification of the initial step of reaction. ...Propagation of mesons and nucleons within a nucleus is described by the Intra-Nuclear Cascade (INC) model. Simulations and preliminary experimental data for the deuteron target obtained at GRAAL are presented.
A photon beam for ELFE at desy D'Angelo, A.; Bellini, V.; Breuer, M. ...
Nuclear Physics A,
08/1997, Letnik:
622, Številka:
1-2
Journal Article, Conference Proceeding
Recenzirano
The Compton backscattering technique may be used to produce highly polarized and tagged photon beams of low background. The general characteristics of these beams are outlined and the application of ...this technique to the ELFE electron facility at HERA is discussed in order to obtain a photon beam in the multi-GeV energy range.
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