The spectrum of tetraquark states with hidden charm is studied within an effective QCD Coulomb gauge Hamiltonian approach. Of the four independent color schemes, two are investigated, the $(q\bar{ c})_1(c\bar{ q})_1$ singlet-singlet (molecule) and the $(qc)_3(\bar{ q}\bar{ c})_3$ triplet-triplet (diquark), for selected $J^{ PC}$ states using a variational method. The predicted masses of triplet-triplet tetraquarks are roughly a GeV heavier than the singlet-singlet states. There is also an interesting flavor dependence with $(q\bar{ q})_1(c\bar{ c}_1)$ states about half a GeV lighter than $(q\bar{ c})_1(\bar{ q}c)_1$. The lightest $1^{ ++}$ and $1^{ --}$ predictions are in agreement with the observed X(3872) and Y(4008) masses, respectively, suggesting they both have a $\omega J/ \psi$ rather than $D^*\bar D^*$ molecular type structure. This is consistent with observed $X$, $Y$ decays to $\pi^\pm J/ \psi$ and not $D^*\bar D^*$ .
Categories: hep-ph