From the deuteron to deusons, an analysis of deuteronlike meson-meson bound states

A systematic study of possible deuteronlike two-meson bound states, deusons, is presented. Previous arguments that many such bound states may exist are elaborated with detailed arguments and numerical calculations including, in particular, the tensor potential. This tensor potential which is crucial for the deuteron binding is shown to be very important also in the mesonic case. In the heavy meson sector one-pion exchange alone is strong enough to form at least deuteronlike B anti B* and B* anti B* composites bound by approximately 50 MeV. Composites of D anti D* and D* anti D* states bound by pion exchange alone are expected near the thresholds, while in the light meson sector one generally needs some additional short range attraction to form bound states. Within the light meson sector pion exchange gives strong attraction for P anti V and V anti V systems with quantum numbers where the best non-q anti q candidates exist, although pion exchange alone is not strong enough to support such bound states. Thus, although one cannot conclude with certainty, this fact does favour the picture that the η(1440) and the f1(1420) are mainly K anti K* composites and the f0(1710) mainly a K* anti K* bound state while the f0(1515) and f2(1520) could be predominantly (ρρ±ωω)/√2 composites. If the predicted D anti D* and D* anti D* states are found, these would support this interpretation of the light states. In channels with exotic flavour or CP quantum numbers pion exchange is generally repulsive or quite weak. Therefore one does not expect that such deuteronlike bound states exist, although B*B* may be an exception. (orig.)