[en] The paper discusses the status of the study of electric polarizability and intrinsic charge radius of the neutron as for the end of 20th century. Recent experimental data in the field of low energy physics are presented. The current theoretical version of the problem interpreting these data is also discussed. 17 refs

[en] The sets in Euclidean spaces are determined, which are the images of the mappings, performed by certain systems of functionals, from a set Ω in the Hilbert space H² of functions analytic in the unit disk. These sets express the correlations established by the elements of Ω between the functionals of the systems. Physically they give, for the functionals chosen, the correlation by experimental data between the pion charge radius, the pionic contribution to the muon magnetic moment and an Euclidean (or equivalent Chebyshev) measure of errors. (author)

No abstract available

[en] Muonic hydrogen (atom hydrogen in which the electron has been replaced by a muon) has been used to determine the proton radius. This determination is deduced from the measurement of the muon bond energy. This method is more accurate than the method based on the electron bond energy and the value obtained (0.8418 ± 0.0007) fm is unexpectedly lower than the previous value (0.877 ± 0.007) fm, which may challenge some predictions given by quantum electrodynamics. (A.C.)

No abstract available

[en] Here the 2S₁₂ – 2P₁₂ energy level shift of the π-gm atom is studied. It is shown that an experimental determination of the 2S₁₂ – 2Pf₁₂ energy level shift accurate to one part per thousand can provide an independent determination of the pion charge radius.

[en] Hofstadter's experiments [1,2] and experimental data for nucleus radii [3] allow to consider nucleons space objects of sufficient dimension. To clarify initial concept [4,5,6] it's necessary to evaluate radii of other hadrons. The evaluation could be performed under the assumption [4,5] of equal increment of these radii R_n= nd (n=1,2,3..., d-constant). Numerical values of such evaluations using tabular mass values (radii are given in Fermi, masses - in MeV) are in table 1.Variations of hadron radii increment in d_n,n-1 = R_n-R_n-1 (table 2) can be the effect of some incorrectness of the accepted suppositions.Thus the experiment points to the approximated persistence of radius increment (d∼0,2)

[en] We construct the correlation between the mean squared pion charge radius rsub(π)sup(2) and the pionic contribution asub(μ)(π⁺π^-) to the muon magnetic moment by means of spacelike data for the pion form factor and investigate the dependence of the correlation on errors of these data. We put into evidence, in the correlation picture, regions of (sometimes very high) instability of the conditional bounds of these magnitudes with respect to errors (and also with respect to each other). The existence of such instabilities in the physically interesting part of the correlation picture asks for extreme care in the interpretation of numerical values for the (conditional) bounds, considered without reference to this picture. (author)

[en] We formulate the information about the mean squared pion charge radius rsub(π)sup(2) and the pionic contribution asub(μ)(π⁺π^-) to the muon magnetic moment, contained in spacelike data for the pion form factor, in terms of a three-dimensional set Δ(d). This set expresses, for the class of all (real) analytic functions f(z) in the unit disk |<1 and normalized to f(0) = 1, to which the pion form factor belongs, the correlation between the values of rsub(π)sup(2), asub(μ)(π⁺π^-) and their distances d(f) to the data. The correlation is computed for two forms of the distance: an Euclidean distance chi(f) related to the usual chi² and a Chebyshev distance π(f), which controls the deviations in the data points individually. It implies bounds for rsub(π)sup(2) and asub(μ)(π⁺π^-) and characterizes their stability properties and their dependence on the chosen form of d(f). (author)

[en] QCD sum rules for processes with small momentum transfers are used to calculate the values of the charge radii of the proton and neutron. The results obtained are in good agreement with the experimental values