Leptonic decays of heavy pseudoscalar mesons
Gershtein S.S., Khlopov M.Yu.
It is indicated that Si/(4) symmetry breaking due to the increased mass of the s and с quarks can lead to an appreciable fraction of two-particle lepton decays of heavy (charmed) pseudoscalar mesons. The difference between the experimental values of the vector and axial Cabibbo factors can be explained within the framework of the developed model.