Аннотация
The branching fractions of the decays [Formula: see text] and [Formula: see text] are calculated in the chiral quark NJL model. The decays exist due to the mass difference between [Formula: see text]- and [Formula: see text]-quarks leading to [Formula: see text] and [Formula: see text] mixing. Two different approaches are applied: the approximate calculation of this process, taking into account the transitions [Formula: see text] and [Formula: see text] explicitly without diagonalization and a more precise approach consisting in the diagonalization of the singlet and octet states leading to the physical fields [Formula: see text], [Formula: see text] and [Formula: see text]. The obtained results are in satisfactory agreement with current experimental data.