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 $\mu_p G_{Ep}(Q^2)/G_{Mp}(Q^2)$ 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 $e^{-}p$ process by the Rosenbluth technique) with recent Jefferson Lab data on the ratio $G_{Ep}(t)/G_{Mp}(t)$ (measured in precise polarization $\overrightarrow{e}^{-}p\to e^{-}\overrightarrow{p}$ 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 $|G_{Ep}(t)|$ around $t=-Q^{2}=-13$GeV$^{2}$. The new behaviour of $G_{Ep}(t)$ 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 analitički 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 električni faktor oblika u prostornom području izvedenim Rosenbluthovom metodom, su u skladu sa svim poznatim svojstvima faktora oblika, uključivši i QCD asimptotičke vrijednosti. Međutim, oni zahtijevaju nultu vrijednost (tj., difrakcijski minimum) protonskog električnog faktora oblika oko t=15 GeV2 . To mijenja naše 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 $He^3$ and $H^3$, 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 $X$ 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 analitički 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 električni faktor oblika u prostornom području izvedenim Rosenbluthovom metodom, su u skladu sa svim poznatim svojstvima faktora oblika, uključivši i QCD asimptotičke vrijednosti. Međutim, oni zahtijevaju nultu vrijednost (tj., difrakcijski minimum) protonskog električnog faktora oblika oko t=15 GeV2 . To mijenja naše 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 ω and φ 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 ω-φ 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 analitičkih modela za strane prijelazne faktore oblika pseudoskalarnih mezona koji ovise samo o omjerima konstanti vezanja ω and φ mezona kao slobodnim parametrima. Iznosi tih omjera se određuju iz odnosnih prijelaznih faktora oblika pseudoskalarnih mezona upotrebom posebnog miješanja ω-φ 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