54 research outputs found
Manifestation of the JLab proton polarization data on the behaviour of strange nucleon form factors
Special eight-resonance unitary and analytic model of nucleon electromagnetic
structure is used to analyze, first the classical proton form factor data
obtained by the Rosenbluth technique and then also the contradicting JLab
proton polarization data on the ratio with the
aim to investigate a manifestation of the latter on the strange nucleon form
factors behaviour.Comment: Latex, 9 pages, 3 figures. Talk given at the PAVI06 International
Workshop, 16-20 May, 2006, Milos, Greec
Unitary and analytic model of nucleon EM structure, the puzzle with JLab proton polarization data and new insight into proton charge distribution
The Unitary and analytic model of nucleon electromagnetic structure,
describing all existing nucleon form factor data, is briefly reviewed. Then in
the framework of this model the problem of inconsistency of older proton
electric form factor data in space-like region (obtained from process by the Rosenbluth technique) with recent Jefferson Lab data on
the ratio (measured in precise polarization
experiment) is suggested
to be solved in favour of the latter data which, however, unlike older data
cause an existence of the form factor zero, i.e. a difraction minimum in
around GeV. The new behaviour of
with the zero gives modified proton charge distribution with enlarged value of
the mean square charge radius.Comment: 9 pages, 11 eps figures. Talk presented at the workshop on Lepton
Scattering and the Structure of Hadrons and Nuclei, Erice (Italy), September
200
Polarizacijski podaci za protone iz JLaba i globalni unitarni i analitiÄki model EM strukture nukleona
It is demonstrated that the new JLab proton polarization data, which are in a rather strong disagreement with the proton electric form factor data in the space-like region obtained by the Rosenbluth technique, are consistent with all known form factor properties, including also the QCD asymptotics. However, they require the existence of a zero value (i.e. a diffraction minimum) of the proton electric form factor around t=15 GeV2. That leads to a change of our understanding of the charge distribution inside the proton.Pokazujemo da novi polarizacijski podaci iz JLaba za protone, koji su u velikom neskladu s podacima za protonski elektriÄni faktor oblika u prostornom podruÄju izvedenim Rosenbluthovom metodom, su u skladu sa svim poznatim svojstvima faktora oblika, ukljuÄivÅ”i i QCD asimptotiÄke vrijednosti. MeÄutim, oni zahtijevaju nultu vrijednost (tj., difrakcijski minimum) protonskog elektriÄnog faktora oblika oko t=15 GeV2 . To mijenja naÅ”e poznavanje raspodjele naboja u protonu
New sum rules for nucleon and trinucleon total photoproduction cross-sections
Two new sum rules are derived relating Dirac radii and anomalous magnetic
moments of the considered strongly interacting fermions with the convergent
integral over a difference of the total proton and neutron, as well as
and , photoproduction cross-sections.Comment: 1 eps figure. Contribution presented at the PHOTON'03, April 7-11,
2003, Frascati (Roma), Ital
Sum rule for a difference of proton and neutron total photoproduction cross-sections
Starting from very high energy inelastic electron-nucleon scattering with a
production of a hadronic state to be moved closely to the direction of the
initial nucleon, then utilizing analytic properties of parts of forward virtual
Compton scattering amplitudes on proton and neutron, one obtains the relation
between nucleon form factors and a difference of proton and neutron
differential electroproduction cross-sections. In particular, for the case of
small transferred momenta, one finally derives sum rule, relating Dirac proton
mean square radius and anomalous magnetic moments of proton and neutron to the
integral over a difference of the total proton and neutron photoproduction
cross-sections.Comment: LaTeX2e, 7 pages, 1 eps figure (revised version
Polarizacijski podaci za protone iz JLaba i globalni unitarni i analitiÄki model EM strukture nukleona
It is demonstrated that the new JLab proton polarization data, which are in a rather strong disagreement with the proton electric form factor data in the space-like region obtained by the Rosenbluth technique, are consistent with all known form factor properties, including also the QCD asymptotics. However, they require the existence of a zero value (i.e. a diffraction minimum) of the proton electric form factor around t=15 GeV2. That leads to a change of our understanding of the charge distribution inside the proton.Pokazujemo da novi polarizacijski podaci iz JLaba za protone, koji su u velikom neskladu s podacima za protonski elektriÄni faktor oblika u prostornom podruÄju izvedenim Rosenbluthovom metodom, su u skladu sa svim poznatim svojstvima faktora oblika, ukljuÄivÅ”i i QCD asimptotiÄke vrijednosti. MeÄutim, oni zahtijevaju nultu vrijednost (tj., difrakcijski minimum) protonskog elektriÄnog faktora oblika oko t=15 GeV2 . To mijenja naÅ”e poznavanje raspodjele naboja u protonu
Faktori oblika pseudoskalarnih mezona od vektorske struje stranih kvarkova
Similarly to the electromagnetic pseudoscalar-meson transition form factors, one can also define strange-quark vector current pseudoscalar-meson transition form factors, contributing only to the behaviour of the isoscalar parts of the former ones. Their explicit form is found by constructing unitary and analytical models of the strange pseudoscalar-meson transition form factors dependent only on Ļ and Ļ coupling constant ratios as free parameters. Numerical values of these ratios are then determined from the corresponding pseudoscalar-meson transition form factors by employing the Ļ-Ļ mixing and a special assumption on the coupling of the quark components of vector-meson wave functions to the flavour component of currents under consideration.Poput elektromagnetskih prijelaznih faktora oblika pseudoskalarnih mezona, mogu se definirati i prijelazni faktori oblika pseudoskalarnih mezona od vektorske struje stranih kvarkova, koji doprinose samo svojstvima izoskalarnih dijelova prvih. Njihova se eksplicitna formulacija nalazi razvijanjem unitarnih i analitiÄkih modela za strane prijelazne faktore oblika pseudoskalarnih mezona koji ovise samo o omjerima konstanti vezanja Ļ and Ļ mezona kao slobodnim parametrima. Iznosi tih omjera se odreÄuju iz odnosnih prijelaznih faktora oblika pseudoskalarnih mezona upotrebom posebnog mijeÅ”anja Ļ-Ļ i posebnom pretpostavkom o vezanju kvarkovskih komponenata valnih funkcija vektorskih mezona na okusnu komponentu studiranih struja
The elastic electron-deuteron scattering beyond one-photon exchange
We discuss the elastic ed scattering beyond Born approximation. It is shown
that the reaction amplitude contains six generalized form factors, but only
three linearly independent combinations of them (we call them generalized
charge, quadrupole and magnetic form factors) contribute to the reaction cross
section in the second order perturbation theory. We examine two-photon exchange
and find that it includes two types of diagrams, when two virtual photons
interact with the same nucleon and when the photons interact with different
nucleons. Estimations based on nonrelativistic calculations with the deuteron
wave function for realistic NN potential show that the main contribution to the
generalized charge, quadrupole and magnetic form factors comes from diagrams of
the first type.Comment: v2, published version in PR
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