9,489 research outputs found
Polarization phenomena in elastic scattering, for axial parametrization of two-photon exchange
We analyze polarization phenomena for elastic lepton-nucleon scattering,
parametrizing the -exchange contribution, as the product of lepton and
nucleon axial vector currents, that correspond to exchange in the
annihilation channel. We found two combinations of polarization observables
(one for three T-odd observables and another one - for five T-even
observables), which allow to measure the ratio of nucleon
electromagnetic form factors in model independent way, without any specific
assumption about the -exchange mechanism. Both these combinations have
a general character and do not depend on the choice of the spin structure for
the -exchange. We show the inconsistency of other approximations
recently used in the literature.Comment: Eight pages, no figure
Radiative corrections to polarization observables for elastic -scattering. Part I: Virtual Compton Scattering
We calculate polarization phenomena for virtual Compton scattering on
protons, at relatively large momentum transfer 1 GeV 5
GeV on the basis of a model for with two main
contributions: -exchange in channel and -excitation in
-channel. This model applies from threshold to region. The
parameters entering in this model, such as coupling constants and
electromagnetic form factors are well known. The analyzing powers for
and the components of the final proton
polarization in are large in absolute value and
show strong sensitivity to interference. These results
can be applied to the calculation of radiative corrections to polarization
phenomena in elastic -scattering.Comment: 18 pages, 9 figure
Recent results on hadron form factors
We discuss the recent data on the electric proton form factor, obtained at
JLab, which show a spectacular deviation from the commonly assumed dipole
behavior. We discuss the implication of these results on the deuteron structure
and on the neutron electric form factor: at relatively large a revision
of the deuteron models may be required, and the neutron electric form factor
might become even larger than the proton electric form factor.Comment: 17 pages 4 figures Contribution to the Int. Workshop on Relativistic
Nuclear Physics from hundreds of MeV to TeV, Varna, Bulgaria, 10-16 September
2001. Replacement of Fig. 1 and relative tex
Polarization phenomena for meson production in nucleon-nucleon collisions
We analyze polarization phenomena for pseudoscalar and vector mesons
production in nucleon-nucleon collisions. We identify three energy regions
corresponding to different physics and different approaches in the analysis of
polarization effects. In the threshold region, characterized by the S-wave
production for all final particles, the general symmetry properties of strong
interaction can be applied. The region of intermediate energies, T=2-4 GeV, is
characterized by the essential role of central i.e. non-peripheral collisions,
where only a small number of s-channel states with definite quantum numbers,
and , contribute. At higher energies, T 10 GeV, the
leading mechanism is the diffractive dissociation and it is especially
interesting for baryon spectroscopy. The transition to this region is an open
field for experimental research at the Nuclotron.Comment: 25 pages, 9 figures Int. Workshop on Relativistic Nuclear Physics
from Hundreds of MeV to TeV, Varna, Bulgaria, 10-16 September 200
Sensitivity of pQCD deuteron structure to the nucleon form factors
We discuss the applicability of pQCD to the elastic scattering of electrons
on protons and deuterons. We analyze the -dependence of the reduced
deuteron form factor, taking into account the recent data on the electric
proton form factor and we find that the value of the QCD-scale parameter
differs essentially from the value GeV, previously
found using the dipole parametrization of the electromagnetic nucleon form
factors and . Moreover the predicted scaling behavior of the reduced
deuteron form factor can not be recovered in the Dirac and Pauli
representations for the nucleon electromagnetic form factors
QCD-view on hadron form factors in space-like and time-like momentum transfer regions
QCD gives definite predictions for hadron electromagnetic form factors in
space-like and time-like momentum transfer regions, such as the quark counting
rules, the hypothesis of hadron helicity conservation, and the relations
between nucleon and deuteron form factors in the formalism of reduced nuclear
matrix elements. Recent precise data about these form factors, obtained in
polarization experiments at the Jefferson Laboratory, have essentially changed
our view on this subject. QCD-predictions do not apply to these data up to
=5-6 GeV for deuteron and for the electric form factor of proton. An
analysis of these data suggests that the asymptotic region will more probably
start at =20-25 GeV. We show that the separation of magnetic and
electric proton form factors in the time-like region represents the most
stringent test of the asymptotic regime and QCD-predictions.Comment: 10 pages, 4 figures, Contribution to the 10th International
Conference on Nuclear Reacton Mechanisms, Varenna, Villa Monastero, Italy,
June 9-13, 200
Strong and electromagnetic interaction views on deuteron structure
The purpose of this contribution is to give an outlook of recent results
connected with deuteron physics, with electromagnetic and strong interacting
probes at intermediate energy. Special attention will be devoted to
polarization observables.Comment: 11 pages 5 figures Int. Workshop 'Relativistic Nuclear Physics: From
Hundreds MeV to TeV' Stara Lesna, Slovakia, June 26-July 1, Slovak Republi
Nuclear processes in magnetic fusion reactors with polarized fuel
We consider the processes , , , , , with particular attention for applications in fusion reactors. After
a model independent parametrization of the spin structure of the matrix
elements for these processes at thermal colliding energies, in terms of partial
amplitudes, we study polarization phenomena in the framework of a formalism of
helicity amplitudes. The strong angular dependence of the final nuclei and of
the polarization observables on the polarizations of the fuel components can be
helpful in the design of the reactor shielding, blanket arrangement etc..We
analyze also the angular dependence of the neutron polarization for the
processes and .Comment: 33 pages 4 figure
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