G. I. Gakh

Two-component model for the deuteron electromagnetic structure

We suggest a simple phenomenological parametrization for the deuteron electromagnetic structure, and show that a good fit on all available data for the three deuteron electromagnetic form factors (in the range Q{sup 2}{<=}2 GeV{sup 2}) can be obtained with a small number of parameters. The present description of the deuteron is based on two components with different radii, one corresponding to two nucleons separated by {approx_equal}2 fm, and a standard isoscalar contribution, saturated by {omega} and {phi} mesons, only.

Polarization effects in the reaction

The electron positron annihilation reaction into four-pion production has been studied, through the channel e(+)+e(-)-> (rho) over bar+rho. The differential (and total) cross sections and various polarization observables for this reaction have been calculated in terms of the electromagnetic form factors of the corresponding gamma(*)rho rho current. The elements of the spin-density matrix of the rho meson were also calculated. Numerical estimations have been done, with the help of phenomenological form factors obtained in the spacelike region of the momentum transfer squared and analytically extended to the timelike region.

e^++e^-\to \rho^+ +\rho^-

The annihilation reaction e + + e ! ¯ � + � is considered. The constraint on time-like �-meson form factors from the measurement done by the BaBar collaboration at p s = 10.5 GeV is analyzed.

and determination of the

The dependence of the differential cross section and polarization observables in the

\rho -

\bar N+N\to \pi +e^++e^-

meson form factors in the time--like region

reaction on the polarizations of the proton target and antiproton beam (the produced electron may be unpolarized or longitudinally polarized) have been derived in a general form using hadron electromagnetic current conservation and

Experimental constraint on the ρ meson form factors in the time-like region

P-

General analysis and numerical estimations of polarization observables in thep¯+p→π0+e++e−reaction in an exclusive experimental setup

invariance of the hadron electromagnetic interaction. The analysis was done for the case of an exclusive experimental setup where the produced electron and pion are detected in coincidence. The explicit dependence of all polarization observables on two, from five, kinematic variables (the azimuthal angle

Experimental constraint on the

\varphi

\rho -

and the virtual-photon parameter