The six-quark structure of long-lived $D$-mesons and $\psi/J$

The harmonic quarks are applied to the analysis of quark structures of long-lived $D$-mesons and $\psi/J$. In the harmonic quark model the quarks of long-lived mesons ($\pi^0$, $\pi^\pm$, $K^\pm$, $K^0$, $B^0$, $B^\pm$) are weakly relativistic objects with the excess energy of valent quarks less than 7 MeV. In contrast to this, the long-lived $D$-mesons in two-quark standard have the apparent excess energies of a few hundred MeV. It was established that all long-lived $D$-mesons and $\psi/J$ have the six-quark structures. There are two valent quarks and two additional neutral quark-antiquark $u$-pairs. The quark structures of $D^0$, $D^\pm$, $D_s^\pm$ and $\psi/J$ are given. The excess energies of six-quark $D$-mesons also does not exceed 7 MeV. A six-color quark composition and the absence of two-quark $D$-mesons in the context of QCD are discussed.