Isospin breaking of the narrow charmonium state of Belle at 3872 MeV as a deuson

The narrow charmonium state near 3872 MeV reported by the Belle Collaboration and confirmed by CDF lies almost exactly at the D-0(D) over bar*(0) threshold. As was predicted many years ago it can be a D (D) over bar* deuteronlike meson-meson state called a deuson. If so, its spin-parity should be 1(++), or possibly 0(-+), and its isospin predominantly 0. An important decay mode should be via D-0(D) over bar*(0) to D-0(D) over bar (0)pi(0). Large isospin breaking is expected because of the isospin mass splitting between the neutral and charged D (D*) mesons. Because of this large isospin breaking the decay X(3872)--> J/psip would be allowed, while J/psisigma a would be forbidden by C-parity, as indicated by the present data. (C) 2004 Published by Elsevier B.V.