94 research outputs found
Multipole Extraction: A novel, model independent method
A novel method for extracting multipole amplitudes in the nucleon resonance
region from electroproduction data is presented. The method is based on
statistical concepts and it relies heavily on Monte Carlo and simulation
techniques; it produces precise identification and determination of the
contributing multipole amplitudes in the resonance region and for the first
time a rigorous determination of the associated experimental uncertainty. The
results are demonstrated to be independent of any model bias. The method is
applied in the reanalysis of the Bates and Mainz data.Comment: Proceedings, "Shape of Hadrons" Workshop, 27-29 April 2006, Athens,
GREEC
On hadron deformation: a model independent extraction of EMR from pion photoproduction data
The multipole content of pion photoproduction at the
resonance has been extracted from a data set dominated by recent Mainz
Microtron (MAMI) precision measurements. The analysis has been carried out in
the Athens Model Independent Analysis Scheme (AMIAS), thus eliminating any
model bias. The benchmark quantity for nucleon deformation, , was determined to be ,
thus reconfirming in a model independent way that the conjecture of baryon
deformation is valid. The derived multipole amplitudes provide stringent
constraints on QCD simulations and QCD inspired models striving to describe
hadronic structure. They are in good agreement with phenomenological models
which explicitly incorporate pionic degrees of freedom and with lattice QCD
calculations.Comment: 14 pages, 9 figures, 2 table
Momentum distributions and spectroscopic factors of doubly-closed shell nuclei in correlated basis function theory
The momentum distributions, natural orbits, spectroscopic factors and
quasi-hole
wave functions of the C12, O16, Ca40, Ca48, and Pb208 doubly closed shell
nuclei, have been calculated in the framework of the Correlated Basis Function
theory, by using the Fermi hypernetted chain resummation techniques. The
calculations have been done by using the realistic Argonne v8' nucleon-nucleon
potential, together with the Urbana IX three-body interaction. Operator
dependent correlations, which consider channels up to the tensor ones, have
been
used. We found noticeable effects produced by the correlations. For high
momentum values, the momentum distributions show large enhancements with
respect to the independent particle model results. Natural orbits occupation
numbers are depleted by about the 10\% with respect to the independent particle
model values. The effects of the correlations on the spectroscopic factors are
larger on the more deeply bound states.Comment: Modified version of the previous paper (there are new figures). The
paper has been accepted for publication in Physical Review
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