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Simple relations between the masses of the two lightest up and down quarks were obtained on the basis of the simple physically based model compatible with the present-day theory of strong interactions, i.e. with quantum chromodynamics. Relations between the u- and d- quark masses, on one hand, and nucleon and pion masses, on the other hand, are also established. The u- and d-quark masses mu = 1,903 MeV, md = 4,594 MeV, calculated with the help of the obtained relations, are in very good agreement with the modern evaluations and calculations of these quantities. The average of the u and d quark masses mud = 3,248 MeV, obtained in the proposed approach, is also in good agreement with previous calculations. [ABSTRACT FROM AUTHOR]

Charge dependence of the pion-nucleon coupling constants and the 1 0 S -state low-energy nucleon-nucleon scattering parameters are studied on the basis of the Yukawa meson theory. The charge independence breaking effect in the pionnucleon coupling constants is entirely explained by the mass difference between the charged and the neutral pions and by the mass difference between the proton and the neutron. Using of well-known pseudovector pion-nucleon coupling constant   0 2 0.0749 7 pp f   , which characterize the proton-proton nuclear interaction, we calculate the charged   2 0.0802 7 c f  and the neutral   2 0 f  0.0750 7 pion-nucleon coupling constants, and also the pion-nucleon coupling constant   0 2 0.0751 7 nn f   , which characterize the neutron-neutron nuclear interaction. With the help of the obtained coupling constants, we also calculate values of the low-energy np- and nn-scattering parameters, which appear to be in good agreement with the experiment. [ABSTRACT FROM AUTHOR]

Charge independence breaking (CIB) in the pion-nucleon coupling constant and the nucleon-nucleon scattering length is considered on the basis of the Yukawa meson theory. CIB effect in these quantities is almost entirely explained by the mass difference between the charged and the neutral pions. Therewith charge splitting of the pionnucleon coupling constant is almost the same as charge splitting of the pion mass. Calculated difference between the proton-proton and the neutron-proton scattering length in this case comprises ~90% of the experimental value. [ABSTRACT FROM AUTHOR]