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

Abstract

The narrow charmonium state near 3872 MeV reported by the Belle collaboration and confirmedby CDF lies almost exactly at the neutral D anti-D* threshold. As was predicted many years ago it can be a deuteronlike meson-meson state called a deuson. If so, it should be an axial, or possibily a pseudoscalar state with C=0, and isospin predominantly 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) to J/psi rho would be allowed, while J/psi sigma would be forbidden by C-parity, as indicated by the present data.