A. F. Krutov

Relativistic properties of spin and pion electromagnetic structure

The role of the Wigner spin rotation effects in the electromagnetic structure of pion is investigated. Pion is considered as quark-antiquark system in the framework of the instant form relativistic hamiltonian dynamics. It is shown that the spin rotation effects give the important contribution to the pion mean square radius, to the pion form factor at the intermediate momentum transfers and to the form-factor asymptotic behaviour. The calculations are performed with the different model wave functions. It is shown that the contribution of the spin rotation depends weakly on the model for the interaction of quarks in pion.

Asymptotic estimation of some multiple integrals and the electromagnetic deuteron form factors at high momentum transfer

A theorem about asymptotic estimation of multiple integrals of a special type is proved for the case when the integrand peaks at the integration domain boundary, but not at a point of extremum. Using this theorem, the asymptotic expansion of the electromagnetic deuteron form factors at high momentum transfers is obtained in the framework of a two-nucleon model in both the nonrelativistic and relativistic impulse approximations. It is found that the relativistic effects slow down the decrease of deuteron form factors and result in agreement between the relativistic asymptotics and experimental data at high momentum transfers.

Definition of the waist plane for general astigmatic Gaussian beams.

We propose a possible generalization of the waist plane for a two-dimensional astigmatic Gaussian beam as a plane of minimal spot area of the beam during propagation. It is shown that the defocusing component of the beam phase vanishes in this plane. Some examples of astigmatic Gaussian beams and corresponding area waist planes are presented and discussed.

Electromagnetic structure of the proton within the CP-violation hypothesis

The so-called non-Rosenbluth behavior of the proton electromagnetic form factors can be explained within the hypothesis of CP violation in electromagnetic processes involving composite systems of strongly interacting particles. It is shown that this hypothesis leads to the appearance of an additional, anapole, form factor of the proton. The proton electromagnetic form factors, including the anapole form factor, are estimated on the basis of experimental data on elastic electron-proton scattering.

Pion form factor in time like region in a framework of relativistic composite quark model

The analytical properties of the pion form factor in the complex plane of momentum transfers are discussed in the Poincaré-invariant quark model. It is shown, that these analytical properties are similar to ones following from basic principles of quantum field theory. The strong dependence of pion form factor on the type of the pion wave functions is obtained in the time-like momentum transfers region. The conditions of resonance behavior of the form factor in this region are formulated in our model. The simple examples of wave functions giving the resonance behavior of the form factor are constructed.

Relativistic constituent quark model and experiments at JLab

Within the relativistic-quantum-mechanics version developed by the present authors in their previous studies, the pion electromagnetic form factor is calculated in the region of high momentum transfers reached and planned to be reached in experiments at the Thomas Jefferson Laboratory (JLab). An asymptotic expansion was obtained for the pion form factor for Q2 → ∞. This expansion describes well existing experimental values and the results of a QCD simulation of future experiments at JLab. It is shown that the region of experiments at JLab is an asymptotic region for the relativistic constituent quark model and that the behavior of the pion form factor, Fπ(Q2)Q2 = const, can be obtained within this model.

Relativistic asymptotics of the deuteron and pion form factors

We present an investigation of the electromagnetic structure of the deuteron and the pion in a relativistic approach in the range of future JLab experiments. It is shown that this range could be considered as asymptotical for these systems. An asymptotical analysis of the deuteron and pion form factors is performed. We find that our relativistic calculations coincide with pQCD predictions if some restrictions are imposed.

Contribution of meson-exchange currents to the electromagnetic structure of the deuteron at high momentum transfers

The leading term of the asymptotic expansion of the contributions of the πNN and ρπγ processes to the electromagnetic form factors of the deuteron at high momentum transfers is calculated. The resulting asymptotic behavior is compared with experimental data obtained at the Thomas Jefferson Laboratory. Constraints on the functional dependence of meson-nucleon vertex functions that ensure a correct asymptotic behavior of deuteron form factors are discussed.

Mathematical analysis of the asymptotic behavior of the electromagnetic deuteron form factors at high momentum transfer

A theorem about asymptotic estimation of multiple integral of a special type is proved for the case when the integrand peaks at the integration domain bound, but not at a point of extremum. As an example of application of this theorem the asymptotic expansion of the electromagnetic deuteron form factors at high momentum transfers is obtained in both nonrelativistic and relativistic impulse approximations. It is found that relativistic effects slow down the decrease of deuteron form factors and result in agreement between the relativistic asymptotics and experimental data at high momentum transfers. The presence of quark degrees of freedom is investigated.