We use the method of QCD sum rules in the presence of an external pion field to investigate isospin symmetry breakings in pionnucleon couplings. Possible manifestations of such isospin symmetry breaking are examined in the context of low-energy nucleonnucleon (NN) scattering. We discuss numerical results in relation to both the existing data and other theoretical predictions.

Deuteron electrodisintegration cross section in threshold region has been calculated by using the Kisslinger's hybrid quark-hadron model, including isoscalar MEC. The appearance of the second maximum can be explained by the dependence of cross section on , and may be the signal of six-quark clusters.

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